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Cosmology / Gravitation Posters: Abstracts

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1101: Cosmokinetics

Authors: M. A. Amin(Stanford University/KIPAC), R. D. Blandford(Stanford University/KIPAC), E. A. Baltz(KIPAC), P. J. Marshall(KIPAC)

Our fundamental lack of understanding of the acceleration of the Universe suggests that we consider a kinematic description. The simplest formalism involves the third derivative of the scale factor through a jerk parameter. A new approach is presented for describing the results of astronomical observations in terms of the jerk parameter and this is related to the equation of state approach. Simple perturbative expansions about flat Lambda-CDM are given.

1102: Creation of a Brane World with Gauss-Bonnet Term

Authors: Koh-suke Aoyanagi, Kei-ichi Maeda (Waseda University)

We study the creation of a brane world using an instanton solution.We analyze brane models with a Gauss-Bonnet term in a bulk spacetime.The curvature of 3-brane is assumed to be closed, flat, or open.We construct instanton solutions with branes for our models,and calculate the value of the actions to discuss the initial state of a brane universe.

1103: The Cause of the Present Cosmic Acceleration

Authors: Arbab, A.I. (Riyadh Teachers' College, Saudi Arabia)

We have shown the the present cosmic acceleration is due to the fact that the gravitational force is increasing with time. In this universe the cosmological constant evolves with time. For the universe to remain critical acceleration has to increase to counteract the increasing strength of gravity. The consequences of this model on the earth moon are investigated in the study of the Earth-Moon system and the data obtained agree with observation.

1104: Generation of Large-Scale Magnetic Fields from Dilaton Inflation in Noncommutative Spacetime

Authors: Kazuharu Bamba and J. Yokoyama (Osaka University)

The generation of large-scale magnetic fields is studied in dilaton electromagnetism in noncommutative inflationary cosmology taking into account the effects of the spacetime uncertainty principle motivated by string theory. We show that it is possible to generate large-scale magnetic fields with sufficient strength to account for the observed fields in galaxies and clusters of galaxies through only adiabatic compression without dynamo amplification mechanism in models of power-law inflation based on spacetime noncommutativity without introducing a huge hierarchy between the dilaton's potential and its coupling to the electromagnetic fields.

1105: Dark Matter and Dark Energy from a Single Scalar Field

Authors: Silvio A. Bonometto, Roberto Mainini, Loris Colombo (Universita' di Milano-Bicocca/INFN Milano)

The Peccei Quinn (PQ) solution of the strong-CP problem implies the existence of axions, which are a viable candidate for DM. We show that the PQ approach can be modified so to yield also DE, in fair proportions, without tuning any extra parameter. DM and DE arise from a single scalar field and are weekly coupled in the present epoch. Flucutations are shown to have a fair evolution. The model is fitted to WMAP first wear release, using a MCMC technique and performs as well as LCDM, coupled or uncoupled dynamical DE. Best fit cosmological parameters for different models are mostly within 2 sigma's. The main peculiarity of the model is to favor high values of the Hubble parameter.

1106: A New Theory of Spontaneous Decay Resolves Paradoxes of General Relativity, Quantum Mechanics, and Cosmology

Authors: Avtar Singh, Sc. D. (MIT Alumni)

A new mathematical theory, the Gravity Nullification model (GNM), is proposed for integrating the missing physics of the spontaneous decay of particles into the existing physics theories, specifically the general theory of relativity, without altering its original formulation. The integration of GNM addresses the following key questions raised by the High Energy Physics Advisory Panel (HEPAP) of the National Science Foundation: - Are there undiscovered principles of nature? - How can we solve the mystery of dark energy? - Are there extra dimensions of space? - Do all the forces become one? - What is dark matter? - How did the universe come to be? - What happened to the antimatter? The above questions, and many others described in the present paper that plague the flagship theories of physics today point to the missing physics in these theories. A new relativistic wave-particle model has also been developed using GNM, which explains both the observed classical as well as quantum behaviors. It also resolves the observed paradox of relativity theory related to the action-at-a-distance or non-locality observed in quantum experiments. GNM also closes the gap between quantum mechanics and theory of relativity by extending the validity of the gravity formulation of general relativity into the quantum scale without a singularity. This approach is then used to predict the observed behavior of the universe and resolves the following shortcomings of the widely accepted Big Bang Model (BBM) without resorting to the incredible scenario of inflation involving “superluminal expansion” during the early evolution of the universe: - Singularities in the initial conditions of BBM (black hole singularity) - Horizon problem - Flatness problem - Cosmological constant problem The theory presented in this paper restores simplicity and beauty to physics to enhance its credibility, comprehensibility, and acceptance. It also restores the once lost elegance to the “Absurd Universe” (Michael S. Turner, Astronomy Magazine, 2004), predicted by the current theories.

1107: Formation of Primordial Black Holes After Inflation

Authors: Kathleen A.Thompson (SLAC)

We examine the formation of primordial black holes (PBH's) in the very early Universe. We are interested in scenarios in which there was a period of inflation and some of the inflationary quantum perturbations evolve far enough into the nonlinear regime that PBH's form. Our goal is to reliably extrapolate from a given inflation model to a spectrum of initial PBH masses.

1108: Two Astrophysical Phenomena in Higher Dimensional Cosmology

Authors: Sujit Chatterjee (New Alipore College, India)

Higher dimensional spacetime is now an active field of research in its attempts to unify gravity with other types of interactions as also to address the problem of hierarchy in field theory.Utilizing an earlier solution[1] of the present author the bahavior of the Luminosuty distance and Nucleosynthesis is discussed in the framework of higher dimensional spacetime.It is found that for models satisfying, q > -1 ( where q is the deceleration parameter)the deSitter universe allows for the maximum luminosity distance.The restriction, q > -1 is quite realistic as corroborated in Tinsley's pioneering work[2].This , however , extends to higher dimension an earlier work of Barnes[3] in this field. Higher dimensional spacetime is particularly relevant in the early Universe before it underwent the compactification transition.Following elementary thermodynamical considerations we have been able to show that in the multidimensional cosmology the isotropic backgound temperature falls off less rapidly compared to the analogous 4D case.This fact has profound influence in the process of nucleosynthesis because it takes relatively more time for the elementary particles to cool below their critical temperature causing delayed decoupling phase of the elementary particles (neutrinos, for example).It is also observed that the ratio, Q/H (where Q is the reaction rate and H is the background expansion rate) is more sensitive to temperature fluctuations in multidimensional cosmology.This fact may have its relics in the present day universe, which may be amenable,in principle at least, to observational checks. References: 1.Chatterjee,S. and Bhui, B. : MNRAS (1990) 247, 57. 2.Tinsley,B.M. : Physics Today 91977) 30, 32. 3. Barnes,R.C. : MNRAS (1981), 959.

1109: A Simple Model of Accelerating Universe in Higher Dimensional Spacetime

Authors: Sujit Chatterjee (New Alipore College, India)

Recent evidence based on measurements of anisotropies in the cosmic microwave background by DASI, BOOMerang and MAXIMA groups along with the observational results coming from the type Ia supernovae suggest that most of the energy in the universe consists of some form of dark energy that is gravitationally self repulsive and is causing the expansion of the universe to accelerate. Naturally there has been of late a surge of interests in obtaining exact cosmological solutions which can account for this acceleration. While the volume of work in 4D in accelerated universe is enormous ,we are not aware of models of similar kind in higher dimensional spacetime.But higher dimensional spacetime is now seriously pursued as an important field of activity in its partial success in unification through various Kaluza-Klein schemes as well as string theory models. Recent intrusion to brane world is another success story. Motivated by these considerations we have,in this work, obtained an exact solution in 5D homogeneous model exhibiting the above feature of accelerated expansion. The line element is taken as ds^{2}= dt^{2}- R^{2}(t)(dr^{2} + r^{2}d\theta^{2} + r^{2}sin^{2}\theta d\theta^{2}) - A^{2}(t)dy^{2} where R and A are the 3D and extra dimensional scale factors respectively.The generalised Einstein's field equations yield either R = sinh^{1/2}t or R = sinh^{3/4}t with corresponding extra dimensional scale as A = sinh^{3/4}t(a- b cotht) or A = cosht sinh^{-5/4}t + sinh^{3/4}t ln tanh(t/2). Encouraging to point out that as time evolves the extra dimension shows the desirable feature of dimensional reduction so that the model ultimately ends up as an effective 4D world. Further the behavior of the 3D scale factor shows that the the deceleration parameter, q is positive initially (which is a good thing for structure formation), becomes zero at some instant and then becomes negative. This result is quite interesting vis a vis the current attempts to construct accelerating models as in quintessential universe. We have further noted that asympototically our model mimics a steady state type of Universe as advocated by Bondi and Gold as also Hoyle and Narlikar although it originates from a bigbang type of singularity.Consequent to dimensional reduction the effective temperature profile as also the entropy generation in the 4D world are also calculated. The fact that enough entropy is being pumped onto the 4D world as a result of dimensional reduction prompts us to suggest an alternative resolution of the vexed problems of flatness and horizon of the Universe. The new temperature profile is also utilized to briefly study its influence on primordial nucleosynthesis.

1110: Casimir Effect in a Supersymmetry-Breaking Brane-World as Dark Energy

Authors: Pisin Chen (SLAC), Je-An Gu (National Taiwan University)

A new model for the origin of dark energy is proposed based on the Casimir effect in a supersymmetry-breaking brane-world. Supersymmetry is assumed to be preserved in the bulk while broken on a 3-brane. Due to the boundary conditions imposed on the compactified extra dimensions, there is an effective Casimir energy induced on the brane. The net Casimir energy contributed from the graviton and the gravitino modes as a result of supersymmetry-breaking on the brane is identified as the observed dark energy, which in our construction is a cosmological constant. We show that the smallness of the cosmological constant, which results from the huge contrast in the extra-dimensional volumes between that associated with the 3-brane and that of the bulk, is attainable under very relaxed conditions.

1111: Flavor and Chiral Oscillations with Dirac Spinors

Authors: Alex Eduardo de Bernardini (IFGW-State University of Campinas), Stefano De Leo (Imecc-State University of Campinas)

In the standard treatment of particle oscillations the mass-eigenstates are implicitly assumed to be {\em scalars} and, consequently, the spinorial form of neutrino wave functions is {\em not} included in the calculations. To analyze this additional effect, we discuss the oscillation probability formula obtained by using the Dirac equation as evolution equation for the neutrino mass-eigenstates. The initial localization of the spinor state also implies an interference between positive and negative energy components of mass-eigenstate wave packets which modifies the standard oscillation probability. The Dirac formalism is useful and essential in keeping clear many of the conceptual aspects of quantum oscillation phenomena that naturally arise in a relativistic spin one-half particle theory. Our study leads to the conclusion that the {\em fermionic} nature of the particles and the interference between positive and negative frequency components of mass-eigenstate wave packets modify the standard oscillation probability. Nevertheless, under particular assumptions, i.e. ultra-relativistic particles and strictly peaked momentum distributions, and when chiral oscillations are taken into account, these modifications introduce correction factors proportional to m/p_0^2 which are practically un-detectable by any experimental analysis.

1112: Modified Chaplygin Gas and Accelerated Universe

Authors: Ujjal Debnath (Jadavpur University)

In this lecture, we shall consider a model of modified Chaplygin gas and its role in accelerating phase of the universe. We have assumed that the equation of state of this modified model is valid from the radiation era to $\Lambda$ CDM model. We have used recently developed state-finder parameters in characterizing different phase of the universe diagrammatically.

1113: Dark Matter from Extra Dimensions

Authors: J.A.R. Cembranos, A. Dobado, A.L. Maroto (Universidad Complutense de Madrid)

Low energy excitations of Brane-World models are characterized by two main parameters: The fundamental D-dimensional scale of gravity M and the brane tension T=f^4. When f is very large compared with M, graviton production is the most important new effect in these models. However, for f << M, the brane excitations called branons became the most important low-energy modes. Branons are stable, weakly interacting and can be massive. They are natural WIMPs candidates for dark matter in these models and they could be probed in future underground and collider experiments.

1114: Age Constraints and Fine Tuning in Variable-Mass Particle Models

Authors: Urbano Franca, Rogerio Rosenfeld (Instituto de Fisica Teorica, Unesp)

VAMP (VAriable-Mass Particles) scenarios, in which the mass of the cold dark matter particles is a function of the scalar field responsible for the present acceleration of the Universe, have been proposed as a solution to the cosmic coincidence problem, since in the attractor regime both dark energy and dark matter scale in the same way. We find that only a narrow region of values for the overall energy scale of the potential lead to models with viable values for the Hubble constant and dark energy density today. In the allowed region, the dark energy density starts to dominate around today and consequently such models can not solve the coincidence problem. We show that the age of the Universe in this scenario is considerably higher than the age for non-coupled dark energy models, and conclude that more precise independent measurements of the age of the Universe would be useful to distinguish between coupled and non-coupled dark energy models.

1115: Modular Cosmology Phenomenology: Its Difficulties and Possible Resolutions

Authors: Kenji Kadota(Fermilab)

The existence of ubiquitous moduli fields is a generic feature of string/M-theory and cosmology scenario where moduli play crucial roles is a rather natural consequence and of great interest from the viewpoint of string/M-theory phenomenology. I will discuss a modular cosmology scenario where the difficulties usually encountered in conventional modular cosmology scenarios (such as dilaton stabilization, cosmological moduli/gravitino problems, lepto/baryogenesis, unnatural fine-tuning for the desirable cosmic perturbations and the initial condition problems for inflaton moduls) are solved in a self-consistent manner. I shall also discuss the predictions of the resultant cosmic perturbations which can be tested by future CMB experiments such as Planck as well as the indication of our leptogenesis scenario in view of future accelerator experiments such as Large Hadron Collider.

1116: Large Enhancement of KK Dark Matter Annihilation Rate Due to Threshold Singularity

Authors: Mitsuru Kakizaki, Shigeki Matsumoto and Masato Senami (ICRR, University of Tokyo)

We reconsider pair annihilation processes of dark matter in the framework of universal extra dimensions, in which all the standard model particles propagate. In such scenarios, as a consequence of Kaluza-Klein(KK) parity the first excitation mode of the B boson is a viable candidate of cold dark matter, and the Fourier expanded modes are almost degenerate in mass at each KK level. We point out that the KK dark matter annihilation cross section is significantly enhanced due to the threshold singularity in the non-relativistic limit. Consequently the predicted positron flux is increased compared with that at the tree level. The operative and future positron experiments will serve as good probes to distinguish physics beyond the standard model.

1117: Nambu-Goldstone Bosons in CP Violating Theory with Majorana Masses

Authors: Darwin Chang (National Tsing Hua University), Wai-Yee Keung (UIC), Chen-Pin Yeh (National Tsing Hua University)

We derive some properties of the Nambu-Goldstone boson coupling in theories that have CP violation and Majorana masses. We show explicitly that its diagonal coupling to a Majorana fermion is pseudoscalar not scalar.

1118: Possible Observation of a Cosmic String

Authors: O.S. Khovanskaya, M.V. Sazhin (Sternberg Astronomical Institute, Moscow), M. Capaccioli (Osservatorio Astronomico di Capodimonte, Naples), G. Longo (Univ. Federico II, Naples)

The Capodimonte-Sternberg-Lens candidate No. 1 (CSL-1) is a peculiar double source discovered in the Osservatorio Astronomico di Capodimonte -- Deep Field (OACDF) (Sazhin, M. et al., MNRAS 343 2 2003, 353-359.). Based on the OACDF data, follow-up spectroscopy and gravitational lensing models, we have ruled out all interpretations other than two: the unlikely projection effect of two identical galaxies at z=0.46 (Khovanskaya, O.S., et al., submitted to Astron. Zhurnal 2004, in russian.), or the first case of gravitational lensing by a cosmic string. Detailed modeling shows that these two scenarios can be easily disentangled by using high angular resolution imaging. We also discussed a statistical excess of gravitational lens candidates present in OACDF region surrounding CSL-1 (Sazhin, M.V. et al., accepted to Pis'ma v Astron. Zhurnal 2004, astro-ph/0406516.). The excess of gravitational lenses (if it will be confirmed by more precise spectroscopic investigations) can not be explain on the basis of conventional gravitational lens statistic alone, but is compatible with the proposed cosmic string scenario. Confirmation of the cosmic string hypothesis would allow us to derive the first measurement of the energy scale of symmetry breaking and of the energy scale of Grand Unified Theory, and will open a new way to investigate fundamental physics using astronomical instruments.

1119: The Universe: Cosmological Model in the Beginning of XXI Century

Authors: Vladimir Lukash (Astro Space Centre of Lebedev Physics Institute)

We discuss the progress, problems and puzzles of current cosmological model: initial conditions and inflation parameters, coincidence of LSS and CMB scales, multicomponent dark matter and cosmological parameters, degeneracies between them, minimal model and possible extensions.

1120: The Scale Expanding Cosmos Theory

Authors: C. Johan Masreliez (EST Foundation)

The redshifted light from distant galaxies suggests that the universe expands. The assumption is usually made that there is expansion of the spatial metrics. Spatial expansion naturally leads to the conclusion that the universe originated in a spacetime singularity - the Big Bang. This paper proposes a different mode of expansion that does not imply a Big Bang type creation event. This new model, the Scale Expanding Cosmos (SEC) theory agrees better with observations than the standard model and might resolve several cosmological enigmas including the Pioneer anomaly and the supernovae Ia observational discrepancies.

1121: Dark Energy, Dark Matter and the Exchange of Matter between the Bulk and the Brane in Randall-Sundrum Cosmology

Authors: G. J. Mathews (University of Notre Dame), K. Umezu, K. Ichiki, T. Kajino (NAOJ), M. Yahiro (Kyushu University)

We study the cosmological brane-world scenario in which the exchange of mass-energy between the bulk dimension and the bane is allowed. The evolution of matter fields on the brane is then modified by new terms in the five-dimensional energy momentum tensor. In this talk we investigate constraints from various cosmological observations on such exchange between the bulk and the brane. We show that it is possible to have a consistent cosmology with no cosmological constant for an observer in the brane. This model also accounts for the suppression of the CMB power spectrum at low multipoles. The observed cosmic acceleration in this case is attributable to the so-called "dark radiation" associated with the projection of the flow of matter from the bulk to the brane. A peculiar aspect of this cosmology is that the universal dark matter content may be significantly larger. Its influence, however, is offset by the dark-radiation term. Possible observational tests of this new cosmological paradigm will be suggested.

1122: Structure Formation through Cosmic Bose Einstein Condensation -Unified View of Dark Matter and Energy-

Authors: Masahiro Morikawa (Ochanomizu University)

We propose a cosmological model that some boson field condensates and forms dark energy/matter. Negative pressure associated with the condensate is analyzed through the Gross-Pitaevskii equation and yields the accelerated cosmic expansion as well as the rapid collapse of the smallest scale density fluctuations. Various types of non-linear collapse are studied. We show that such collapse forms many black holes without violating matter and CMB power spectrum observed. The repetition of this sedimentation/collapse cycles yields the self organized critical structure in which the ratio (Dark Matter/Dark Energy) becomes about 1. This work is the extension of our previous study in astro-ph/0403571.

1123: Rotating Brane Worlds and the Global Rotation of the Universe

Authors: Alan Guth (Massachusetts Institute of Technology), Ali Nayeri (Institute for Fundamental Theory)

We introduce a new class of brane worlds with slowly rotating black holes in the branes' Anti de Sitter bulks. The introduction of the slowly rotating {\it Kerr} black holes in the bulk modifies the dynamics of the brane worlds, depending on the angular momentum of the bulk black holes. In this letter, we discuss the metric and dynamics of the {\it rotating} brane worlds with arbitrary topology due to the bulk Kerr black holes to the first order of the black holes' angular momentum. We show that the brane world rigidly rotate and the cosmic fluid on the brane gains an intrinsic kick in the azimuthal direction, while the Friedmann equations on the brane remain intact. Any deformations to the shape of the brane and any mortifications to the Friedmann equations depend on the square of angular momentum and will not appear in this talk.

1124: Studying the Decay of the Vacuum Energy with the Observed Density Fluctuation Spectrum

Authors: Reuven Opher, Ana Pelinson (University of Sao Paulo)

One of the major problems in cosmology today is to explain the observed acceleration of the universe. The present observational data are consistent with the simplest solution to this problem, which is based on the vacuum energy. A decaying vacuum energy is a very attractive solution. It could link the value of the present vacuum energy, that is accelerating the universe today, with the value that created the inflationary epoch in the past. We investigate here models that suggest that the vacuum energy decays into cold dark matter (CDM) and show that the density fluctuation spectrum obtained from the cosmic microwave background (CMB) data together with large galaxy surveys (e.g., the Sloan Digital Sky Survey), puts strong limits on the rate of decay of the vacuum energy. CDM produced by a decaying vacuum energy would dilute the density fluctuation spectrum, created in the primordial universe and observed with large galaxy surveys at low redshifts. Our results indicate that the decay rate of the vacuum energy into CDM is extremely small.

1125: A Breakthrough of Moduli Problem and Baryogenesis in a Minimal Model

Authors: Donghui Jeong(KAIST), Kenji Kadota(Fermi Lab), Wan-Il Park(KAIST), wan D. Stewart(KAIST)

we propose a simple model in which MSSM plus neutrino mass term, (LH_u)^2 is supplemented by a minimal flaton sector to drive the thermal inflation, and make two crucial assumptions: the flaton vacuum expectation value generates the mu-term of the MSSM and m_L^2 + m_{H_u}^2<0. we show that our model leads to thermal inflation followed by Affleck-Dine leptogenesis along the LH_u flat direction.

1126: Towards a Complete Theory of Thermal Leptogenesis in the SM and MSSM

Authors: Antonio Riotto (INFN)

We perform a thorough study of thermal leptogenesis adding finite temperature effects, RGE corrections, scatterings involving gauge bosons and by properly avoiding overcounting on-shell processes. Assuming hierarchical right-handed neutrinos with arbitrary abundancy, successful leptogenesis can be achieved if left-handed neutrinos are lighter than 0.15 eV and right-handed neutrinos heavier than 2 10^7 GeV (SM case, 3sigma C.L.). MSSM results are similar. Furthermore, we study how reheating after inflation affects thermal leptogenesis. Assuming that the inflaton reheats SM particles but not directly right-handed neutrinos, we derive the lower bound on the reheating temperature to be T_RH > 2 10^9 GeV. This bound conflicts with the cosmological gravitino bound present in supersymmetric theories. We study some scenarios that avoid this conflict: 'soft leptogenesis', leptogenesis in presence of a large right-handed (s)neutrino abundancy or of a sneutrino condensate.

1127: Dark Matter Abundance in Brane Cosmology

Authors: Osamu Seto (Sussex U.)

We investigate the thermal relic density of a cold dark matter in brane world cosmology. It is found that the resultant relic density can be considerably enhanced compared to that in the standard cosmology. The consequence of the neutralino dark matter also is shown.

1128: Approach to the Cosmological Constant Problem with a Diluting Mechanism by Extra-Dimensions

Authors: Satsuki Shimono (Kyoto University)

The cosmological constant problem (CCP) that a value of the cosmological constant has a gap of order 120 between observations and the standard theory has been considered hard to overcome while few ten's of years. Recently a mechanism of diluting the cosmological constant by an extra dimensional effect has thought up by Dvali et al.(2003). That said that the crude cosmological constant is the Planck scale and exist in the (4+n)-dimensional entire space, and we observe this diluted in the 4-dimensional brane embedded. We have constructed the n-dimensional spherically symmetric extra space to examine the diluting mechanism and studied the relation between the number of extra-dimensions and the observed effective cosmological constant. As a result, the diluting mechanism has been realized and concluded that n>=3 is needed to overcome the CCP.

1201: Gauge-Invariant Gravitational Wave Extraction from Coalescing Binary Neutron Stars

Authors: Ken-ichi Oohara (Niigata University)

We report application of a method for extracting gravitational waves to three-dimensional numerical simulation on coalescing binary neutron stars. We found the extracted wave form includes the components corresponding to the quadrupole part in the Newtonian potential of the background metric, if it is monitored at a position not far from the central stars. We present how to eliminate it.

1202: New Black Hole Solutions in the String Gravity with Noncompact Extra Dimensions and Their Experimental Search I

Authors: S.Alexeyev, M.Pomazanov, V.Bykov (Moscow State University), N.Popov (Computer Center of Russian Academy of Sciences), A.Barrau, J.Grain (Joseph Fourier University)

The Gauss - Bonnet invariant is one of the most promising candidates for a quadratic curvature correction to the Einstein action in expansions of supersymmetric string theory. We study these Gauss - Bonnet black holes (and their properties) which could be formed at future colliders if the Planck scale is of order a TeV, as predicted by some modern brane world models.

1203: Chern Simons Gravity, Charges and Entropy

Authors: Rodrigo Aros (Universidad Andres Bello)

In this work the Chern Simons gravity is analyzed, in particular the role of a certain set of boundary conditions for black hole solutions. Those boundary conditions are in a one on one relation the introduction of a particular form for the action, which proves to be sound within the context of this work. Finally the boundary conditions at the horizon determine that algebra of charges of diffeomorphisms be a Virasoro like one

1204: Expected Mass Ratios of Compact Object Binaries Observed in Gravitational Waves

Authors: T.Bulik(Nicolaus Copernicus Astronomical Center), D. Gondek-Rosinska(Observatoire de Paris), K. Belczynski (New Mexico State University)

We use the well tested StarTrack binary population synthesis code to examine the properties of the population of compact object binaries. We calculate the distribution of masses and mass ratios taking into account weights introduced by observability in gravitational waves during inspiral. We find that in the observability weighted distribution of double neutron star binaries there are two peaks: one for nearly equal mass systems, and one for the systems consisting of a low and a high mass neutron star, q=0.6-0.7. The observability weighted distribution of black hole neutron star binaries is concentrated on the systems with the mass ratio q=0.3-0.5, while for the double black hole binaries the observability weighted distribution is dominated by the massive, nearly equal mass binaries with q>0.7.

1205: Black Hole Mergers form Population III Binaries

Authors: T. Bulik (Nicolaus Copernicus Astronomical Center), K. Belczynski (New Mexico State University), B. Rudak (Nicolaus Copernicus Astronomical Center)

Evolution of first population of massive metal-free binary stars is followed. Due to the low metallicity, the stars are allowed to form with large initial masses and to evolve without significant mass loss. Evolution at zero metallicity, therefore, may lead to the formation of massive remnants. In particular, black holes of intermediate-mass (sim 100-500 M_\odot) are expected to have formed in early Universe, in contrast to the much lower mass stellar black holes (sim 10 M_\odot) being formed at present. Following a natural assumption, that some of these Population III stars have formed in binaries, the physical properties of first stellar binary black holes are presented. We find that a significant fraction of such binary black holes coalesces within the Hubble time. We point out that burst of gravitational waves from the final coalescences and the following ringdown of these binary black hole mergers can be observed in the interferometric detectors. We estimate that advanced LIGO detection rate of such mergers is at least several events per year with high signal to noise ratio (\gtrsim 10).

1206: Space Vacuum as a Self-Organizing and Evolving Object (Geometrization of the Phenomenon)

Authors: Vladimir Burdyuzha(Lebedev Physical Institute of Russian Academy of Sciences)

Probably the main element of our world is not the 4-dim continuum of Einstein-Minkowsky. It may be a 4-dim distorted and stratificated geometry of space-time. In this conception of fields vacuum is the state in which geometry of space-time does not deform. The problem of the cosmological constant can not be solved exactly in the terms of the current quantum field theory which works with Higgs and nonperturbative vacuum condensates. It can not fully solved in geometrodynamics of Wheeler-DeWitt also.It is necessary to invent a law of coordination of vacuum subsystems. This law must "govern" vacuum (its evolution). The aim is practically zeroth lambda-term. This is an evident fact that our Universe for cooling was losing the symmetry through relativistic phase transitions. These processes were accompanied by production of vacuum condensates of quantum fields the negative contributions of which have compensated a initial positive vacuum energy (it is phenomenological solution of the problem). Besides, we have introduced into consideration of the cosmological vacuum a gravitational vacuum condensate consiting of topological defects of different dimensions (worm-holes, micromembranes, microstrings and monopoles) of the Planck size. That is the vacuum of the Universe contains some components which were produced by zeroth vibrations of quantum fields, nonperturbative condensates, worm-holes and the gravitation vacuum condensate.

1207: The Quest for Primordial Gravitational Waves

Authors: Asantha Cooray (California Institute of Technology)

I will describe the search for gravitational wave background from inflation indirectly with CMB polarization observations and directly with space-based gravitational wave detectors. The talk will discuss confusions associated with detection techniques in each of these two cases and methods to remove and reduce such contaminants. Finally, we will summarize the physical parameters one can establish on inflation by combining any detections or useful limits from these two methods.

1208: Black Hole Dissolution in Phantom Energy

Authors: E. Babichev, V. Dokuchaev and Yu. Eroshenko (Institute For Nuclear Research of the Russian Academy of Sciences)

Solution for a stationary spherically symmetric accretion of the relativistic perfect fluid with an arbitrary equation of state onto the Schwarzschild black hole is presented. This solution is a generalization of Michel solution and applicable to the problem of dark energy accretion. It is shown that accretion of phantom energy is accompanied with the gradual decrease of the black hole mass. Masses of all black holes tend to zero in the phantom energy universe approaching to the Big Rip.

1209: How Black Holes Get Their Kicks! The Gravitational Radiation Rocket Effect

Authors: Marc Favata (Cornell University), Scott A. Hughes (MIT), Daniel E. Holz (LANL)

Gravitational radiation carries away linear momentum, imparting a "kick" to the center of mass of the radiating system. Using perturbation theory, we have calculated the kcik velocity for binary black holes in the extreme-mass-ratio limit. Our results are accurate for the slow, inspiral phase of coalescence, but less accurate for the final plunge. Scaling relations are used to extrapolate our results to higher mass ratios. Relativistic effects reduce the kick velocity compared to previous quasi-Newtonian estimates. Over a wide range of black hole spins, we find that kick velocities of V ~ 10-100 km/s are likely; V ~ 200-300 km/s are not unexpected; and the largest recoils possible are probably < 500 km/s. These numbers are less than galactic escape speeds, but are comparable to the escape speeds of globular clusters and high redshift mini-halos. Black hole kicks have implications for growing supermassive and intermediate mass black holes, and can also affect the central stellar densities of large galaxies. We will discuss our calculations of the kick velocity, its astrophysical applications, and future work.

1210: Quasi-Periodic Oscillations in Three-Dimensional Relativistic Tori

Authors: P. Chris Fragile, Omer Blaes (University of California, Santa Barbara), Luciano Rezzolla, and Olindo Zanotti (Scuola Internazionale Superiore di Studi Avanzati (SISSA))

Motivated by recent interesting work on p-mode oscillations in axisymmetric black-hole tori by Rezzolla, Zanotti, and collaborators, we explore the stability of these oscillations through three-dimensional relativistic hydrodynamic simulations. Our primary motivation is to find out whether these oscillation modes can survive when the assumption of axisymmetry is relaxed. This is crucial since black-hole tori are known to be susceptible to low-order non-axisymmetric modes, principally the so-called Papaloizou-Pringle instability (PPI). Since accretion can suppress the PPI, we also search for oscillatory behavior in tori undergoing moderate accretion. The key question here is whether this accretion also destroys the resonant cavity needed for the oscillations.

1211: New Numerical Methods to Evaluate Homogeneous Solutions of the Teukolsky Equation

Authors: Ryuichi Fujita (Osaka University), Hideyuki Tagoshi (Osaka University)

We discuss a numerical method to compute the homogeneous solutions of the Teukolsky equation. We use the formalism developed by Mano, Suzuki and Takasugi, in which the homogeneous solutions of the radial Teukolsky equation are expressed in terms of two kinds of series of special functions, and the formulas for the asymptotic amplitudes are derived explicitly. Although the application of this method was previously limited to the analytical evaluation of the homogeneous solutions, we find that it is also useful for numerical computation. As a test, we compute the flux of the gravitational waves induced by a compact star in a circular orbit on the equatorial plane around a Kerr black hole. We find that the relative error of the energy flux is about 10^(-14) which is much smaller than the one derived by numerical integration.

1212: Using Simulation, Comparison and Grid Search To Find All Possible Binary Black Hole Source Parameters For Extreme Mass-Ratio Inspiral Gravitational Wave Signals

Authors: James S. Graber (LOC)

First, for each case to be tested, a specific target inspiral signal is selected for parameter extraction. In a future real analysis, the target signal would be a real signal actually observed by a gravitational wave detector such as LISA. In this study, however, the target signals are themselves simulations. Some cases were selected to resemble sources likely to be detected by LISA when it flies; others were selected to facilitate comparison with previous work using Fisher matrix techniques [e.g. Leor Barack, Curt Cutler, Phys.Rev. D69 (2004) 082005]. Then, for each target inspiral signal, a grid search of the input parameter space is conducted to determine the set of input parameters that produce a simulated inspiral output signal compatible with the target. In this study, we consider four parameters: the two masses, the spin of the larger black hole, and the eccentricity of the orbit. Searching through this four dimensional parameter space requires that hundreds of possible input source parameter combinations be simulated for each target signal analyzed. For each input parameter combination, the detailed time history of the phase of the resulting inspiral is simulated and directly compared with the phase history of the target signal. The simulation, comparison, and grid search technique used in this study requires more work than the Fisher matrix technique used in most previous studies of this topic. However, this method yields a detailed map of the acceptable region of input parameter space, in contrast to the multidimensional ellipsoids of the Fisher matrix method. Nevertheless, the final results are in general agreement with those obtained previously by the Fisher matrix method, providing a partly independent confirmation of both results.

1213: Bending of Light Near a Star, Gravitational Red/Blue Shift and Black-Hole: Alternative Explanations Based on Refraction of Light

Authors: Ramesh C.Gupta (Institute of Engineering & Technology, Lucknow)

Many of the general-relativity-tests such as bending of light near a star and gravitational red/blue shift are explained without general-relativity & without Newtonian-approach. The author first casts doubts on both, the Newtonian and the relativistic approach; and proposes a novel alternative-explanation. The new alternative-explanation is based on refraction-phenomenon of optics. It predicts that as the ray passes through/near the star’s atmospheric-medium, it bends due to refraction-phenomenon towards star-core, like a ray bends while passing through a prism or water-drop. A semi-empirical estimation of the atmospheric-height h and its refractive-index μ are made to find the refraction-results. The refraction-based theory also suggests new explanation for gravitational red/blue shift; it tells that frequency ν remains constant (as it is so in refraction-phenomenon) and the red/blue shift is due to change in wavelength λ due to change in velocity of light c in the medium . Estimated results for bending of light and the red/blue shift etc. with the new approach though agree well with known values, but important thing is that the physics is quite different. Also discussed are black-hole and gravitational-lensing, space-time in the new perspective of refraction. The proposed refraction-based theory proposes a new-look on black-hole, suggesting that black-hole formation is critically due to total-internal-reflection within atmosphere and subsequent absorption into the star-core. Gravitational-lensing is explained as real refraction-lensing with possibility of chromatic-aberration. The new refraction-based theory also makes a few new predictions. The present paper also suggests a possible-alternative to the Einstein’s curved geometry of space-time, and indicates that the 'fabric' of space-time which wraps(curves) around the mass is not the 'empty-vacuum' but the 'atmospheric-medium'. The new refraction-based approach providing alternative to general-relativity, could have important bearing on understanding of space-time, gravity and cosmology !

1214: The Variational Formalism in the Tetrad Gravitational Theory with Non-Linear Lagrangians and Field Equations in the Weyl-Cartan Spacetime

Authors: Valery Korolyov (Moscow State Pedagogical University)

Dilaton matter, considered as a mathematical model for dark matter, generates in spacetime the Weyl-Cartan geometry. We investigate into variational procedure in Weyl-Cartan spacetime with nonmetricity of the Weyl type for non-linear lagrangians of the most general type presented within tetrad gravity theory and obtain gravitational field equations. We use method of independent variation with respect to tetrad and the general nonholonomic connection obeyed Weyl condition with the help undetermined lagrangians multipliers. In order to validate obtained equations we use strong differential identities. Also we showed the equivalence of our variational procedure and other variational methods. The obtained equations are used to investigate into the singularity problem in the early Universe.

1215: Black Hole Formation in Scalar Field Collapse

Authors: Ashutosh Mahajan, Rituparno Goswami, Pankaj S Joshi (Tata Institute of Fundamental Research)

We construct a special class of scalar field collapse model in which black hole is necessarily generated as end product of continual gravitational contraction, rather than a naked singularity. We consider massless scalar field minimally coupled to gravity in four dimensional spherically symmetric spacetime. In the comoving frame massless scalar field can be treated as perfect fluid with equation of state p = rho satisfying an additional condition coming from the Klein Gordon equation for the scalar field. The mass function for the matter is taken separable in the variables which are physical radius of the cloud and time coordinate. Densities, pressures are taken to be smooth or analytic functions at the initial surface. Our results show that the model includes inhomogeneity in density which ends up in black hole, generalizing the collapsing Friedman models.Bouncing of the scalar field is also observed. We present a new non-static solution close to the physical center and show that the dynamical evolution always ends in a simultaneous collapse of all the shells to singularity which necessarily gives rise to a covered central singularity, as there are no outgoing future directed non-spacelike geodesics coming out from the same. It is hoped that dynamical considerations such as these will provide some useful insights into physically realistic collapse and the actual process of black hole formation.

1216: The Role of Primordial Kicks on Black Hole Merger Rates

Authors: Miroslav Micic, Steinn Sigurdsson, Tom Abel(Pennsylvania State University)

The mergers of Pop III BHs with nearby SMBHs may be a prime signal for long wavelength gravitational wave detectors. We distinguish cases in which the BHs are born in the center of high redshift dark matter halos and are endowed with or without intial kick velocities. The central distributions of early BHs in present day galaxies is reduced if they are born even with moderate kicks of tens of km/s. The modest kicks allow the BHs to leave their parent halo which consequently leads to dynamical friction being less effective on the lower mass BHs as compared to their parent halos. Therefore, merger rates may be reduced by more than an order of magnitude.  Using analytical and illustratory cosmological N body simulations we quantify the role of natal kicks of BHs formed from massive metal free stars on their merger rates with SMBHs in present day galaxies.

1217: Entropy of Spinor Fields in 3+1 Dimensional Constant Curvature Black Hole Background

Authors: Banibrata Mukhopadhyay (Harvard-Smithsonian Center for Astrophysics), Kaushik Ghosh (IOPB)

During the last few decades a lot of interests had been devoted to explain the thermodynamical aspects of black holes. Along the way a lot of black hole solutions with nontrivial spacetime geometries have been studied. One of such black hole solution is the (3 + 1)-dimensional constant curvature black hole spacetime. This solution results from an identification of spacetime points in the anti-de Sitter space and represents a higher dimensional generalization of the (2 + 1)-dimensional BTZ black hole. This is constantcurvature black hole with a negative cosmological constant. We consider the thermodynamical aspects of spin-half particles in this spacetime. The Dirac equation is obtained through the Newman-Penrose formalism which is separable only for the massless particles. The density of states of the neutrino field contains divergences associated with the black hole event horizon and also along the bifurcation axis of the constant time foliations. The entropy of the neutrino field is logarithmically divergent in the cut-off parameter.

1218: A Satellite Experiment to Study Anomalous Acceleration in the Solar System

Authors: Daniel Muller (University of Brasilia), Reuven Opher (University of Sao Paulo)

It was recently found that data from the spacecrafts Pioneer 10/11, Galileo, and Ulyssis indicate an anomalous acceleration towards the Sun, which is on the same order as the characteristic acceleration $a_0$ of the MOND (Modified Nonrelativistic Dynamics) theory. A satellite experiment, containing free-floating masses, is proposed to directly measure the anomalous acceleration. We enter into the details of the experiment: 1) its time duration; 2) the contribution of the newtonian gravitational potentials of the planets and the Moon; 3) the position of the satellite; and 4) the displacement of the masses within the satellite during each measurement.

1219: Direct Energy Extraction from Black Holes

Authors: Reuven Opher (University of Sao Paulo)

Charged or rotating black holes (BHs) can, in principle, be a source of considerable energy. This energy source has been suggested as the origin of gamma-ray bursts (GRBs). BHs are formed in the collapse of the cores of massive stars. I show that the plasma density around BHs is always sufficiently high so as to make the mechanisms suggested for energy extraction inviable.

1220: Representation of Canonical Infinite Dimensional Lie Algebra in Spherically Symetric Quantum Collaps

Authors: Marian Pilc (Institute of Theoretical Physics of Charles University in Prague)

Main goal of this work is to quantize a spherically symmetric collapse into the black hole. In order to achieve this one must construct a representation of canonical infinite dimensional Lie algebra of this system. Basic space is set M of positive Borel measures which are equivalent with Lebesgue measure on R. Measure on M is constructed using projective techniques developed by Ashtekar and Lewandowski for Quantum Loop Gravity. Using such measure one can build a kinematical Hilbert space carrying representation of this algebra.

1221: Status and Prospects of Non-Riemannian Cosmology

Authors: Dirk Puetzfeld (Iowa State University)

We provide a rather broad brushed overview of the advancements in building and testing non-Riemannian cosmological models. Cosmological models in non-Riemannian spacetimes may offer an interesting alternative to the dark matter/energy paradigm. In this talk the history of such models is traced back to the early seventies. Recent developments, the observational situation, as well as links to other alternative cosmological scenarios will be discussed.

1222: Research Towards 3rd Generation Gravitional Wave Detectors

Authors: Sheila Rowan (University of Glasgow) for the GEO collaboration

With current long-baseline interferometric gravitational wave detectors in operation on the Earth, and plans in place for first upgrades to these detectors, there is now considerable activity on planning for future more sensitive ‘3rd generation’ gravitational wave interferometers. Possible designs of these detectors are a subject of current research. Discussed here will be topics of research being carried out collaboratively at Glasgow and Stanford Universities on materials for the optics and suspensions of potential instruments. This presentation will include experimental measurements of the loss factor of silicon at room and cryogenic temperatures. This work is of particular relevance to a potential upgrade to the GEO interferometric detector – ‘GEO-HF’.

1223: Gravitational Radiation from Rotating White Dwarfs and Neutron Stars

Authors: David M. Sedrakian (Yerevan State University)

I will summarize main results of collaboration between prof. Matthew Benacquista from Montana State University, Billings, (USA) and Prof. K.Shahabasyan, M. Hayrapetian and A.Sadoyan from Yerevan State University on Gravitational Wave Sources:White Dwarfs and Neutron Stars. Rotating white dwarfs undergoing quasi-radial oscillations can emit gravitational radiation in a frequency range from 0.1-0.3 Hz. Assuming that the energy source for the gravitational radiation comes from the oblateness of the white dwarf induced by the rotation, i.e. deformation energy. The strain amplitude is found to be 10^-25 for a white dwarf at ~ 50pc. We had calculated thermal energy loses through magneto-hydrodynamic mechanism during self similar oscillations to compare with energies emitted in GW band.We examine also possibility of gravitational radiation from white dwarfs undergoing self-similar oscillations which are fed by the energy of the differential rotation of the white dwarf. We consider two cases of angular momentum distribution. Assuming the energy of the self-similar oscillations causing gravitational wave emission is about 10% of the energy dissipated in the differentially rotating white dwarf, the strain amplitudes are again found to be less than 10^-25 for a white dwarf at ~ 50pc. The galactic population of these sources is estimated to be 10^7, and may produce a confusion-limited foreground for proposed advanced detectors in the frequency band between space-based and ground-based interferometers. Nearby oscillating white dwarfs may provide a clear enough signal to investigate white dwarf interiors through gravitational wave astroseismology. We consider also undamped quasi-radial oscillations of the rotating neutron stars and the gravitation radiation generated by them. Two possible sources of energy for maintaining these oscillations are mentioned: the energy of deformation of the decelerating neutron star (spin down) and the energy released during a jump in the star's angular velocity (glitch). Expressions are derived for the intensity of the gravitational radiation and the amplitude of a plane gravitational wave for an earthbound observer. Estimates of these quantities are obtained for the Vela and Crab pulsars, for which the secular variation in the angular velocity is most often accompanied by irregular variations. Particularly the amplitudes of GWs for Vela pulsar is expacted to be of the order of 10^-25 if fed by energy of deformation, and of the order 10^-27 in the case of glitch. It is shown that gravitational waves from these pulsars could be detected by the new generation of Gravitational Wave detectors.

1224: Gravity as a Grand Unification of Forces

Authors: Rasulkhozha S. Sharafiddinov (Institute of Nuclear Physics, Uzbekistan Academy of Sciences)

Any of all possible types of charges corresponds in nature to a kind of the inertial mass. Such a mass - charge duality of matter explains the coexistence of grand united rest mass and charge for the same neutrino equal respectively to its all the gravitational mass and charge which consist of the gravitoelectric, gravitoweak, gravitostrong and a range of others, innate components. From their point of view, a new grand unification theory has been created at the discussion of a question about unification of forces of a different nature. In this theory, the gravitational field must be naturally united gauge field of the unified system of the most diverse combinations of electromagnetic photons, weak bosons and strong gluons where the four pairs of forces of the micro world fundamental interactions are united. Some consequences and laboratory confirmations of the suggested theory have been listed which allow also to define the structure of the graviton as a grand united boson. Thereby it gives the possibility to directly look at the nature of the gravitational matter elucidating the interratio of intraneutrino forces and the problem of elementary particles chiral and mirror symmetries.

1225: Recent Verifications of a New Physical Principle Based on a Particle Mdel Mde Up of Rdiation in Stationary State

Authors: Rafael A. Vera (Universidad de Concepción. Chile.)

In the proceedings of Einstein’s centennial symposium on fundamental physics, 1981, and in the Int. J. of Th. Phys, 20, p 19-50, 1981, a new relativity principle for bodies on different G potentials (GP) was derived from optical physics and a new kind of physics for uncharged particles based on a particle model made up of photons in stationary state. From it, the relative mass-energy of non-local bodies, with respect to observers at rest in a constant GP, is conserved during a free fall and during universe expansion. If a body stops in different G potentials, it releases different energies and gets different relative rest masses, frequencies and lengths. The energy released after a difference of GP comes form the bodies, not from the field. The same principle is verified from correspondence of the Einstein’s equivalence principle and G tests. This one is not consistent with two classical hypotheses: a) the equivalence of standards in different GP, and b), the G field energy. The current compensation of their errors does not eliminate them. The new universe age may be infinite regardless of a universe expansion because the increase of GP expands instruments in same proportion. The universe entropy would be conserved because the new kind of black hole, after absorbing radiation, decays into a gas cloud. Galaxies would be evolving, indefinitely, in nearly closed cycles with luminous and cool periods. Thus all of the phases of a galaxy cycle should be rather uniformly distributed, according to their respective periods, everywhere in the universe. Recent astronomical observations verify the new context fixed by this principle

1226: Shadows (Mirages) Around Black Holes and Retro Gravitational Lensing

Authors: Alexander F. Zakharov, A.A. Nucita, F. DePaolis, G. Ingrosso (Institute of Theoretical and Experimental Physics)

Recently Holz & Wheeler (2002) considered a very attracting possibility to detect retro-MACHOs (which could be a Schwarzschild black hole), which could be illuminated by the Sun. We discuss glories (mirages) formed near rapidly rotating Kerr black hole horizons and propose a procedure to measure masses and rotation parameters analyzing these forms of mirages. In some sense that is a manifestation of gravitational lens effect in the strong gravitational field near black hole horizon and generalization of the retro-gravitational lens phenomenon. We analyze a rapidly rotating Kerr black hole case for some selected positions of a distant observer in respect to the equatorial plane of a Kerr black hole. We discuss glories (mirages) formed near rapidly rotating Kerr black hole horizons and propose a procedure to measure masses and rotation parameters analyzing these forms of mirages. Some time ago Falcke et al. (2000) suggested to search shadows at the Galactic Center. In the paper we present the boundaries for shadows calculated numerically by the authors. We propose to use future radio interferometer RADIOASTRON (or Japanese radio interferometer VERA)facilities to measure shapes of mirages (glories) or shadows around Sgr A* and to evaluate the black hole spin and a position angle of distant observer. It will be the first possibility to observe “faces” of black holes in our galaxy and probably in nearby galaxies.

1227: Observational Signature of Tidal Disruption of a Star by a Massive Black Hole

Authors: Tamara Bogdanovic, Michael Eracleous, Suvrath Mahadevan, Steinn Sigurdsson, and Pablo Laguna (Penn State University)

We have modeled the time-variable profiles of the Halpha emission line from the non-axisymmetric disk and debris tail created in the tidal disruption of a solar-type star by a million solar mass black hole. Two tidal disruption event simulations were carried out using a three dimensional relativistic smooth-particle hydrodynamic code, to describe the early evolution of the debris during the first fifty to ninety days. We have calculated the physical conditions and radiative processes in the debris using the photoionization code CLOUDY. We model the emission line profiles in the period immediately after the accretion rate onto the black hole became significant. We find that the line profiles at these very early stages of the evolution of the post-disruption debris do not resemble the double peaked profiles expected from a rotating disk since the debris has not yet settled into such a stable structure. As a result of the uneven distribution of the debris and the existence of a ``tidal tail'' (the stream of returning debris), the line profiles depend sensitively on the orientation of the tail relative to the line of sight. Moreover, the predicted line profiles vary on fairly short time scales (of order hours to days). Given the accretion rate onto the black hole we also model the Halpha light curve from the debris and the evolution of the Halpha line profiles in time.

1228: General Relativistic Radiation Transfer in Tori

Authors: Steven Fuerst (Mullard Space Science Laboratory (UCL))

We describe a modified version of the Thorne (1981) moment method for solving the problem of general relativistic radiation transfer. The new method is used to investigate the case of scattering in relativistic tori orbiting around Kerr black holes. These tori are thought to exist in AGN where the accretion rate is close to the Eddington limit, where radiation pressure puffs up the center of the accretion disk. Alternatively, hot ion-supported tori may exist in low luminoscity AGN. We use a ray-tracing techinque to construct images of the results, including the effects of higher image orders due to the extreme gravitational lensing near the black hole.

1230: Gravitational Waves in Magnetohydrodynamic Plasmas

Authors: Joachim Moortgat, Jan Kuijpers (Department of Astrophysics Nijmegen)

We study the propagation of gravitational waves (GW) in a uniformly magnetized plasma at arbitrary angles to the magnetic field. No a priori assumptions are made about the temperature, and we consider both a plasma at rest and a plasma flowing out at ultra-relativistic velocities. We find that all 3 fundamental low-frequency plasma wave modes are excited: Alfven waves by a X polarized GW, and the slow and fast magneto-acoustic modes by a + polarized GW. The most relevant mode is the fast magneto-acoustic wave which in a strongly magnetized plasma has a vanishingly small phase lag with respect to the GW allowing for coherent interaction over large length scales. When the background magnetic field is almost, but not entirely, parallel to the GWs direction of propagation even the Alfven waves grow to first order in the GW amplitude. Finally, we calculate the growth of the magneto-acoustic waves and the damping of the GW.

1301: Looking for Signs of Anisotropic Cosmological Expansion in the High-Redshift Supernova Data

Authors: Brett Bochner (Hofstra University)

Several problematical epochs in cosmology, including the recent period of structure formation (and acceleration), require us to understand cosmic evolution during times when the basis of FRW expansion, the cosmological principle, does not completely hold true. We consider that the breakdown of isotropy and homogeneity at such times may be an important key towards understanding cosmic evolution. To study this, we examine fluctuations in the high-z supernova data to search for signs of large-scale anisotropy in the Hubble expansion. Using a model-independent statistical analysis, we find mild evidence of real anisotropy in various circumstances. We discuss the significance of these results, and the importance of further searches for violations of the cosmological principle.

1302: The Status of QUaD

Authors: Sarah Church (Stanford University) and the QUaD Collaboration

QUaD is a ground-based high-sensitivity, high-resolution experiment designed to map the polarization of the Cosmic Microwave Background (CMB) at angular scales of 4 armin to 4 degrees. It is intended to measure the power spectra from E-modes, B-modes, from lensing of the CMB, and B-modes from primordial gravitational waves. The experiment comprises a 2.6m Cassegrain optical system, equipped with an array of 62 polarization-sensitive bolometers (PSBs), located at the South Pole. QUaD will observe at 100 and 150 GHz and will commence operation in late 2004. The expected performance and current status of the experiment will be presented.

1303: WMAP Microwave Emission Interpreted as Dark Matter Annihilation in theInner Galaxy

Authors: Douglas Finkbeiner (Princeton University)

Synchrotron emission from a population of ultra-relativistic electrons in the inner Galaxy has been observed by the Wilkinson Microwave Anisotropy Probe (WMAP). After careful modeling of the microwave foreground signals from Galactic interstellar medium a residual microwave signal is present within 10-20 degrees of the Galactic center, uncorrelated with any known foreground template. The most likely explanation for this mysterious component is synchrotron emission from an unusually hot electron energy distribution. The source of these electrons is still uncertain, but the spatial distribution, inferred energy spectrum, and total number are consistent with their being positron-electron pairs produced by WIMP annihilation.

1304: Estimate of the CMB Fluctuation Amplitude from Dark Energy De-Coherence

Authors: James Lindesay (SLAC), H. Pierre Noyes (SLAC)

Homogeneity and correlations in the observed CMB are indicative of some form of cosmological coherence in earlier times. Cosmological dark energy de-coherence is assumed to occur when the rate of expansion of the cosmological scale parameter in the Friedmann-Lemaitre equations at early times is no longer supra-luminal. This choice of the scale parameter in the FL equations directly relates the scale of dark energy de-coherence to the De Sitter scale (associated with the positive cosmological constant) at late times. It is shown that the class of dynamical models so defined necessarily requires a spatially flat cosmology in order to be consistent with observed structure formation. Prior to de-coherence, the coherence which preserves the uniform density needed to make the FL dynamical equations meaningful must be maintained by supra-luminal (cosmological) correlations and not by the luminal or sub-luminal microscopic exchanges available after de-coherence. The basic assumption is that the dark energy density which is fixed during de-coherence is to be identified with the cosmological constant. No assumptions are made about the constancy of the dark energy density except during the finite time interval when the expansion rate is not supra-luminal. For the entire class of models, the expected amplitude of fluctuations driven by the dark energy de-coherence process is of the order needed to evolve into the fluctuations observed in cosmic microwave background radiation and galactic clustering independent of the scale parameter at de-coherence.

1305: Faraday Rotation of the CMB Polarisation by a Primordial Magnetic Field: Contribution to the BB Angular Power Spectrum

Authors: Juan F. Macias-Perez (LPSC) and Aumont, J. (LPSC)

The magnetic field observed in Galaxies could be explained by a primordial magnetic field of few nG. This magnetic field althoug small will induce a Faraday rotation of the CMB polarisation at the time of recombination. Here we present simulations of this effect for plausible primordial magnetic field distribution and present its contribution to the CMB BB angular power spectrum. Further, we discuss the possible detection of effect with the Planck satellite experiment via component separation methods.

1306: Updated Measurements of the CMB Angular Power Spectrum with Archeops

Authors: Juan F. Macias-Perez (LPSC) on behalf of the Archeops collaboration.

Archeops is a balloon-borne experiment with two frequency bands dedicated to the detection of the CMB anisotropies, 143 and 217 GHz; and two high frequency bands 353 and 545 GHz for the study of galactic foreground contamination. Archeops has measured the CMB angular power spectrum in the range of multipoles going from l=10 to l=700. These measurements are compatible with those from the WMAP team (C.L. Bennett, et.al., 2003, ApJS, 148, 1) indicating that the contamination of these due to SZ effect is negiglible.

1307: Measurements of the Angular Power Spectrum of Polarised Galactic Dust Emission at High Galactic Latitudes with the Archeops Experiment

Authors: Juan F. Macias-Perez (Laboratoire de Physique Subatomique et CosmologieL) on behalf of the Archeops collaboration

The Archeops ballon experiment, mainly dedicated to the measurement of the CMB angular power spectrum at 143 and 217 GHz, has in addition 3 pairs of polarised bolometers at 353 GHz for the study of Galactic dust polarised emission. In A. Benoit et al., 2003 (A&A accepted, astro-ph/0306222) a first detection polarised dust emission on the Galactic plane was presented. Here we discuss the first ever measurement of the angular power spectrum of the dust polarised emission including TT, TE, EE and BB modes. Finally, the possible contamination of the Galactic dust polarised emission to the measurement of the TE CMB spectrum by the WMAP team (C.L. Bennett, et.al., 2003, ApJS, 148, 1) is presented.

1308: Cosmological Perturbations Based on Generalized Gravity Theories Including String Corrections and Tachyon

Authors: Hyerim Noh (Korea Astronomy Observatory) and Jai-chan Hwang (Kyungpook National Univ.)

The classical evolution and quantum generations of the cosmological perturbations are presented based on the generalized gravity thoeries. The string corrections and tachyon are included. Both cases of the scalar and tensor perturbations are studied. This analysis is practically useful to investigate the large scale structure evolution in the universe.

1309: A New Method for Studying the Topology of the Universe from the Cosmic Microwave Background

Authors: Reuven Opher (University of Sao Paulo)

The standard method for observationally confirming the existence of a predicted finite topology of the universe involves searching for the repetition of the same finite or extended source in different directions. However, serious problems are encountered when studying both types of sources, finite and extended. In studying a finite source, such as a star, galaxy, or quasar, the problem of its evolution must be dealt with. The same source seen in different directions is observed at different distances (i.e., ages), making its identification extremely difficult. Studying extended sources, such as circles-in-the-sky (CIS) within the cosmic microwave background (CMB), is also problematic since it requires an unrealistic zero width last scattering surface (LSS) to produce the predicted identical temperatures on the circles. It is shown here that these temperatures are no longer identical when a realistic finite width LSS is taken into account. A new method for studying the topology of the universe which avoids the above mentioned problems in studying both finite and extended sources is suggested here. It consists of searching for increased temperature fluctuations in the regions of the intersections of the LSS with the faces of the fundamental polyhedron of the finite topology. Appreciably greater fluctuations are predicted in these regions. A worked-out example is given.

1310: Observing the Dark Matter Density Profile of Isolated Galaxies from the SDSS Satellite Dynamics

Authors: F. Prada (IAA-CSIC), A. Klypin (NMSU), D. Schlegel (Princeton), J. Holtzman (NMSU), H.-W. Rix (MPIA), E. Grebel (Bassel) et al.

Velocities of satellites of galaxies together with weak lensing provide the best way to probe the mass distribution of individual field galaxies at large radii. Using the Sloan Digital Sky Survey we find that the velocity dispersion of satellites declines with distance to the host galaxy. This decline agrees remarkably well with the distribution of dark matter predicted by the cosmological models in the peripheral parts of galaxies. A relation between the satellite velocity dispersion with the host luminosity as well as new results on the estimation of the host mass-to-light ratio will be presented.

1311: Validity and Application of the Extended Lagrangian Perturbation Theory

Authors: Takayuki Tatekawa (Waseda University)

Basing our discussion on the Lagrangian description of hydrodynamics, we studied the evolution of density fluctuation for nonlinear cosmological dynamics. We solved hydrodynamic equations for a self-gravitating fluid with pressure, given by a polytropic equation of state, using a perturbation method. In this conference, we will discuss validity of these perturbative solutions and application for structure formation in the Universe. Especially we will notice the correspondence between past modified Lagrangian perturbation models and our model.

1401: Microlensing in M31 in the Wide Field Imaging Era

Authors: Edward A. Baltz (KIPAC, Stanford University)

The Andromeda Galaxy (M31) is the closest large galaxy to the Milky Way, thus it is an important laboratory for studying massive dark objects in galactic halos (MACHOs) by gravitational microlensing. Such studies strongly complement the studies of the Milky Way halo using the the Large and Small Magellanic Clouds. We consider the possibilities for microlensing surveys of M31 using the next generation of wide field imaging telescopes with fields of view in the square degree range. We consider proposals for such imagers both on the ground and in space. For concreteness, we specialize to the SNAP proposal for a space telescope and the LSST proposal for a ground based telescope. We find that a modest space-based survey of 50 visits of one hour each is considerably better than current ground based surveys covering 5 years. Crucially, systematic effects can be considerably better controlled with a space telescope because of both the infrared sensitivity and the angular resolution. To be competitive, 8 meter class wide-field ground based imagers must take exposures of several hundred seconds with several day cadence.

1402: The Evolving Structure of Galactic Disks

Authors: Chris Brook (Universite Laval), Daisuke Kawata (Swinburne), Brad Gibson (Swinburne), Hugo Martel (Universite Laval)

Recent observations of distant (z~1) disk galaxies indicate that the ratio of scaleheight to scale length has increased, by a factor of ~1.5, compared with local disk galaxies (Reshitnikov et al. 2003). We examine five simulated disk galaxies, and determine how these structural parameters evolve. Our simulations are performed using GCD+, a parallel galaxy formation code which models gravity using the N-body technique, gas dynamics using Smoothed Particle Dynamics, and includes star formation and supernova feedback. Our results have implications for the formation and evolution of the thin and thick disk components of late type galaxies, within the context of a Cold Dark Matter cosmology.

1403: Testing the Friedmannian Magnitude-Redshift Relation with High-z SNIa

Authors: Marie-No\"elle C\'el\'erier (Laboratoire Univers et TH\'eories (LUTH) Observatoire de Paris-Meudon)

Standard cosmology is constructed upon the (generally implicit) assumption of the "large scale" homogeneity of our universe. Now, structures are observed at scales which become larger and larger as the observational distances increase. However, the homogeneous Friedmann-Lemaitre-Robertson-Walker model remains a cosmological paradigm, and Friedmniannan relations are usually used to work out the model without questions at whether the homogeneity assumption is or not valid at the studied scales. This has been the way the concordance model (LambdaCDM) came out from the analyses of the SNIa data. Since this model implies, without proof, the validity of the Friedmannian magnitude-redshift relation at the range of redshifts spaned by the supernovae surveys, it has been proposed a very simple test of this possible validity, provided the SNIa should be confirmed as standard candles. Since we hope that the redshifts of the supernovae which will be observed in the years to come will allow such a test to be performed, this poster is designed to find inside the SNIa community some collaborators ready to perform the test. If this test should happen to rule out the Friedmannian magnitude-redshift relation, the SNIa data could no more be claimed as a proof for the LambdaCDM model.

1404: Constant Fractal Dimensions of the Galaxy Distribution Varying by Steps?

Authors: Marie-Noelle Celerier (Laboratoire Univers et TH\'eories (LUTH) Observatoire de Paris-Meudon), Reuben Thieberger (Ben Gurion University)

The structure of the large scale distribution of the galaxies have been widely studied since the publication of the first catalogs. Since large redshift samples are available, their analyses seem to show fractal correlations up to the observational limits. The value of the fractal dimension(s) calculated by different authors have become the object of a large debate, as have been the value of the expected transition from fractality to possible large scale homogeneity. Moreover, some authors have proposed that different scaling regimes might be discerned at different lenght scales. To go further on into this issue, we have applied what we consider as the best among the known statistical methods of analysis to the wider sample currently available. We therefore obtain a fractal dimension of the galaxy distribution which seems to vary by steps whose width might be related to the organization hierarchy observed for the galaxies. This result could explain some of the previous results obtained by other authors from the analyses of less complete catalogs and maybe reconcile their apparent discrepancy.

1405: Quasi-Spherical Gravitational Collapse and the Role of Initial Data, Anisotropy and Inhomogeneity

Authors: Subenoy Chakraborty (Jadavpur University)

In this lecture, a detailed study on the role of anisotropy and inhomogeneity will be studied in the context of gravitational collapse in quasi-spherical Szekeres' space-time. Also the role of initial data will be examined in characterizing the final state of collapse. Finally, a linear transformation on the initial data set will be presented and its impact will be discussed.

1406: Measurement of Omega_m, Omega_Lambda from an Analysis of Type Ia Supernovae with CMAGIC: Using Color Information to Verify the Acceleration of the Universe

Authors: A. Conley, G. Goldhaber, L. Wang (LBNL) for the Supernova Cosmology Project

We present Omega_m, Omega_Lambda measurements from a blind analysis of 24 high redshift Type Ia supernovae using a new technique (CMAGIC) for fitting multicolor lightcurves, first introduced in Wang '03. This technique takes advantage of the remarkably simple evolution of Type Ia supernovae on a color magnitude diagram, and has several advantages over more standard techniques that make use of maximum magnitudes. In particular, CMAGIC is intrinsically less affected by extragalactic extinction in a manner that is mostly independent of assumptions about the nature of high redshift dust. This allows us to provide a powerful cross check of previous supernova cosmology results.

1407: Testing the Lambda-Dominated CosmologicalModels by Searching for the Small-Scale HubbleExpansion

Authors: Yurii V. Dumin (IZMIRAN, Rus. Acad. Scis.)

The problem of small-scale Hubble expansion has a long history, started by McVittie (1933). As was shown in the classical works by Einstein and Straus (1945), Noerdlinger and Petrosian (1971), et al., the Hubble effect disappears at small (interstellar and interplanetary) distances. Nevertheless, this conclusion should be reexamined in the context of recent cosmological models, because the previously-used arguments become invalid if the dynamics of space-time is governed by Lambda-term. Some indirect indications to the Hubble expansion inside galaxies were found recently. The same effect in planetary systems can be revealed by comparing the rate of secular increase in the lunar semi-major axis measured by laser ranging with the one derived from the data on Earth rotation deceleration (Dumin, Adv. Space Res. 31, 2461, 2003). The results of such analysis point to a probable small-scale Hubble effect with rate about two times less than at the intergalactic distances. This "residual" expansion may be caused just by the "dark energy" contribution to the energy-momentum tensor.

1408: SALT - A Spectral Adaptive Lightcurve Template for Type Ia Supernovae

Authors: J. Guy, P. Astier, N. Regnault and R. Pain (LPNHE, University of Paris)

We present a new empirical method to estimate the luminosity distances of Type Ia supernovae. The method is based on using a unique spectral template time serie modulated by a function to account for the observed variability of SNe Ia. This Spectral Adaptive Lightcurve Template (SALT) model is adjusted on a training set of well measured photometry points of SNe Ia. The precision of SALT distances is examined by constructing a Hubble diagram with an independent set of Type Ia SNe.

1409: The Evolution of Primordial Magnetic Fields

Authors: Troels Haugboelle, Aake Nordlund (Niels Bohr Institute for Astronomy)

The evolution of primordial magnetic fields in the early universe has until recently mostly been studied using analytical and semi--analytical approaches. Magnetic fields may have a measurable impact on the cosmic microwave background. Furthermore magnetic fields of considerable strength have been found in high red shift galaxies, showing that either the primordial magnetic field was larger than the seed fields considered in dynamo theories or the galactic dynamoes works on a much faster time scale than previously thought. We have developed a 3D general relativistic magneto hydro dynamics code to model the coupling between metric perturbations and a possible turbulent primordial magnetic field. This way we can study ab initio the limits on fields generated either at a phase transition - eg. the electroweak - or during an inflationary epoch, and consider the development of the energy spectrum at different length scales.

1410: Cosmology in the Very Local Universe - Why Flow Models Matter

Authors: Karen L. Masters (Cornell University)

While much of the focus of observational cosmology is on the high redshift universe it is important not to forget the very local universe as a source of cosmological information. The inner profiles and number counts of low mass halos have provided the biggest stumbling block so far for LCDM. These small structures can only be seen nearby. In the very local universe (cz < 3000 km/s) the component of a galaxy's redshift which is due to motions under gravity can be comparable to (or even larger than) its cosmological redshift. The distance to a galaxy as inferred from its redshift can differ by more than a factor of 2 from its actual distance. Given that the mass and intrinsic size scale of a galaxy (among many other physical parameters) depend strongly on its distance, and that these peculiar motions are coherent over large regions of the sky, serious biases can occur. While it is important to have accurate distances to local galaxies, it is not feasible to measure a primary distance for every nearby galaxy. Instead, a velocity field model can be used to provide a first order correction to the redshift distance. We report on a new sample of Tully-Fisher distances (the SFI++) which is being used in combination with publicly available primary distances to model galaxy flows in and around the Local Supercluster. This sample has ~10 times as many tracers as were used for the current best model. Initially a parametric model including infall onto multiple attractors will be used. Such models (which assume spherical symmetry for the attractors) are not realistic representations of the true velocity field, but provide useful first order corrections. Non-parametric reconstructions of the velocity field will follow.

1411: Non-Gaussian Galaxy Distribution

Authors: A. Nakamichi (Gunma Astronomical Observatory), M. Morikawa (Ochanomizu University)

Self gravitating systems (SGS) in the Universe are thought to be non-extensive, and often show long-tails in various distribution functions. Therefore the ordinary Boltzmann statistical mechanics would not be applicable in its naive form. We quantitatively investigate the above non-extensivity and long-tails properties, by introducing four models of statistical mechanics, (1) Boltzmann, (2) Fractal, (3) Renyi, and (4) Tsallis. We use data of redshift survey, apply the count-in-cell method and use Akaike information criteria (AIC) for the fair comparison. Physica A341 (2004) 215-233

1413: SNLS - The SuperNova Legacy Survey : 1st Year Operation.

Authors: Reynald Pain (LPNHE, University of Paris) for the SNLS Collaboration

Type Ia supernovae (SNe Ia) currently provide the most direct evidence for an accelerating Universe and for the existence of an unknown "dark energy" driving this expansion. The 5-year Supernova Legacy Survey (SNLS) will deliver about 1000 SNIa detections with well-sampled griz light curves. Using this definitive dataset, we will obtain a precise measurement of the cosmological parameters (omegam, omegaLambda); our goal is to determine the cosmological equation of state parameter "w" to a statistical precision better than 0.1, testing theories for the origin of the universal acceleration. In this paper, we summarise the progress made during the first full year of the survey operation.

1414: The Spatial Distribution of CIV in the Intergalactic Medium

Authors: Matthew Pieri (Universite Laval, Imperial College London, MPA), Martin Haehnelt (Institute of Astronomy), Joop Schaye (Leiden Observatory, Institute for Advanced Study)

Feedback is a vital component for the modeling of the formation of galaxies and the state of the intergalactic medium. The metal enrichment of the intergalactic medium is a useful probe of such feedback. We investigate the impact of environment on the observed metal absorption in the forest of Lyman alpha absorption lines seen in quasar spectra. Weak CIV absorption is searched for using pixel correlation techniques in regions of the spectrum close to and far from Lyman break galaxies (LBGs) using strong CIV absorption as a proxy for the presence of LBGs near the line of sight. We find that most of the CIV absorption arises close to LBGs and that the volume filling factor of CIV may be lower than the values derived neglecting this spatial correlation.

1415: Gravitational Lensing of Distant Supernovae

Authors: Premana Premadi (Bandung Institute of Technology, Indonesia), Hugo Martel (Universite Laval, Canada)

We use a series of ray-tracing experiments to determine the mean magnification and demagnification of high-redshift sources by gravitational lensing in 3 different cosmologies: a flat, Lambda-dominated universe (Omega0=0.27, lambda0=0.73), an open, low-density universe (Omega0=0.3, lambda0=0), and a flat, matter-dominated universe(Omega0=1, lambda0=0). In all cases, the matter component is in form of Cold Dark Matter (CDM), with a power spectrum normalized to the amplitude of the CMB fluctuations. We determine empirically the relation between magnification and redshift, and use this relation to estimate the effect of lensing on the determination of the cosmological parameters from observations of high-z supernovae.

1416: Cosmochemistry, Cosmology and Fundamental Constants: High-Resolution Spectroscopy of Damped Lyman-Alpha Systems

Authors: R. Quast, D. Reimers (Hamburger Sternwarte), L. Wisotzki (AIP, Germany), A. Smette (ESO, Chile; FNRS, Belgium), C. Ledoux (ESO, Chile), O. Garcet (Institut d'Astrophysique et de Géophysique, Université de Liège), S. Lopez (Universidad de Chile)

Spectroscopy of QSO absorption lines provides essential observational input for the study of nucleosynthesis and chemical evolution of galaxies at high redshift. But some new observations indicate that present chemical abundance data are biased because of deficient spectral resolution and selection effects: Recent high-resolution spectra reveal the hitherto unperceived chemical nonuniformity of individual damped Lyman-alpha (DLA) absorption line system components, and the novel H/ESO DLA survey produces convincing evidence for absorbers exhibiting dust are systematically being missed in present optical DLA surveys. We present a revised analysis of the DLA complex toward HE 0515-4414 showing nonuniform differential depletion of refractory elements onto dust grains, and introduce to the H/ESO DLA survey and its implications. Conclusively, we propose to start an unbiased chemical abundance database established on high-resolution spectroscopic observations. New data to probe the temperature-redshift relation predicted by standard cosmology and to test the constancy of fundamental constants will be potential spin-offs.

1417: Space/Time and Supernovae

Authors: L. Riofrio (San Francisco State University)

EVIDENCE from supernovae and the CMB may support a Relativistic Space/Time. Theory explains CMB horizon and other puzzles without ethereal energies. Redshifts of Type Ia supernovae are a striking confirmation. In review, Principle states that Space and Time are related by R=ct, where R is scale factor and t age of Universe. Gravitation further requires that GM=tc^3, where G is Newton constant. These simple expressions form a solution to Einstein-Friedmann equations with stable density (Omega)=1. Plotted against the curve of supernova redshifts, prediction precisely matches the "accelerating" data. CMB data may also be predicted. Since Space/Time predicts observations not epicycles, Theory should be considered an alternative to more cumbersome ideas. Ref http://www-conf.slac.stanford.edu/ einstein/Talks/SupernovaGraph.pdf

1418: Improving Information on Dark Energy

Authors: P.Ruiz-Lapuente (University of Barcelona)

We quantify the degree of information on w(z) contained in samples of cosmological distance indicators through an inverse problem approach. Without constraining the functional form of w(z), we examine the degeneracies and the resolution limits inherent to this cosmological problem.

1419: Dynamical One-Armed Spiral Instability in Differentially Rotating Stars

Authors: Motoyuki Saijo (Kyoto University), Shin'ichirou Yoshida (University of Wisconsin, Milwaukee)

We investigate the dynamical one-armed spiral instability in differentially rotating stars with both hydrodynamical simulations and perturbative approaches in Newtonian gravity. We find that the one-armed spiral mode is generated around the corotation radius of the star, and the distribution of angular momentum shifts inwards the corotatin radius during the growth of one-armed spiral mode. We also discuss a possible scenario to generate the one-armed spiral mode, and gravitational waves generated from this mode.

1420: Inferring the Dark Matter Power Spectrum from the Lyman-Alpha Forest in High-Resolution QSO Absorption Spectra

Authors: Matteo Viel (Institute of Astronomy, Cambridge), Martin G. Haehnelt (Institute of Astronomy, Cambridge), Volker Springel (MPA)

We use the LUQAS sample (Kim et al. 2004), a set of 27 high-resolution and high signal-to-noise QSO absorption spectra at a median redshift of z=2.25, and the data from Croft et al. (2002) at a median redshift of z=2.72, together with a large suite of high-resolution large box-size hydro-dynamical simulations, to estimate the linear dark matter power spectrum on scales 0.003 s/km < k <0.03 s/km. Our re-analysis of the Croft et al. data agrees well with their results if we assume the same mean optical depth and gas temperature-density relation. The inferred linear dark matter power spectrum at z=2.72 also agrees with that inferred from LUQAS at lower redshift if we assume that the increase of the amplitude is due to gravitational growth between these redshifts. We further argue that the smaller mean optical depth measured from high-resolution spectra is more accurate than the larger value obtained from low-resolution spectra by Press et al. (1993) which Croft et al. used. For the smaller optical depth we obtain a ~ 20% higher value for the rms fluctuation amplitude of the matter density. By combining the amplitude of the matter power spectrum inferred from the Lyman-alpha forest with the amplitude on large scales inferred from measurements of the CMB we obtain constraints on the primordial spectral index n and the normalisation sigma_8. For values of the mean optical depth favoured by high-resolution spectra, the inferred linear power spectrum is consistent with a LambdaCDM model with a scale-free (n=1) primordial power spectrum.

1422: Hot Spot Ignition in Degenerate White Dwarfs: Prelude to a Supernova

Authors: Lewis J. Dursi (CITA, University of Toronto)

While a consensus is building on at least the basics of burning in the `middle' of a Type Ia supernova, the ignition that starts burning, and possible detonation that ends burning remains mysterious. We examine the ignition process in detail, including the cases of flames, detonations, and Zeldovich `strange' modes. Very accurate requirements for ignition under a variety of conditions are given.

1423: Relativistically Compressed White Dwarfs near Black Holes: A New Paradigm for Type I Supernovae

Authors: Grant J. Mathews (University of Notre Dame), J. R. Wilson, D. S. P. Dearborn (LLNL)

We present calculations indicating the a mechanism for Type I supernovae whereby general relativistic terms enhance the self gravity of a carbon-oxygen white dwarf as it passes or orbits near a black hole. Relativistic compression causes the central density to exceed the threshold for pycnonuclear reactions so that a thermonuclear runaway ensues. We consider three possible environments: 1) white dwarfs orbiting a low-mass black hole; 2) white dwarfs encountering a massive black hole in a dense globular cluster; and 3) white dwarfs passing a supermassive black hole in a dense galactic core. Event rates out to a redshift of z~1 are estimated to be significantly less than the rate f normal Type Ia supernovae for all three classes. Nevertheless, such events may be frequent enough to warrant a search for this new class of supernova. We propose several observable signatures which might be used to identify this type of event and speculate that such an event might have produced the observed "mixed-morphology" SgrA East supernova remnant in the Galactic core.

1424: Spectroscopic Observations of Supernovae at z = 0.15 - 0.35

Authors: Masao Sako (KIPAC/Stanford), Roger Romani (Stanford), Josh Frieman (Fermilab/U. Chicago), Steve Kahn (KIPAC/Stanford), Roger Blandford (KIPAC/Stanford), Jen Adelman-McCarthy (Fermilab), Fritz DeJongh (Fermilab), Ben Dilday (U. Chicago), Jared Kaplan (Stanford), Rick Kessler (U. Chicago), Hubert Lampeitl (Fermilab), and John Marriner (Fermilab)

We present results of follow-up spectroscopic observations with the Hobby-Eberly Telescope (HET) of supernovae (SNe) discovered by the Sloan Digital Sky Survey (SDSS) southern equatorial scan. Transient SN-like events are detected in real-time and photometric measurements are made in the five SDSS filter bandpasses with a cadence of ~2 days. Candidate type Ia events are pre-selected based on their colors and light curve behavior, and the HET performs follow-up spectroscopic observations of those with peak magnitudes of r >~ 21 mag, which correspond to SNe Ia at approximately z > 0.2, with the primary goal of confirming types and measuring their redshifts. These SNe will fill in the sparsely sampled redshift interval of z = 0.1 - 0.35 in the Hubble diagram. Detailed investigation of the spectral properties of these moderate-redshift SNe Ia will also provide a bridge between local SNe and high-redshift objects, and will help us understand the systematics for future cosmological applications that require high photometric precision. Finally, the large survey volume also provides the opportunity to select unusual supernovae for spectroscopic study that are poorly sampled in other surveys. For example, color/photo-z cuts can allow the selection of luminous type Ibc's, such as those possibly associated with GRBs. We report on early observations from this program and discuss future potential applications.

1425: Dark Energy Survey and the Camera

Authors: William Wester (FNAL) for the Dark Energy Survey Collaboration

We describe the proposed Dark Energy Survey and Camera. The survey will image 5000 square degrees in the southern sky and collect 300 million galaxies, 30,000 galaxy clusters, and 2000 Type Ia supernovae. We expect to derive a value for the dark energy equation of state parameter, w, to a statistical precision of ~5%, using four distinct measurement techniques. The survey will be carried out using a 3 square degree mosaic camera with increased sensitivity in the near infrared. The camera will be mounted at the prime focus of the 4m Blanco telescope at CTIO.

1426: Safety in numbers: lensing and high-z supernovae

Authors: Daniel Holz (Los Alamos National Laboratory)

Gravitational lensing compromises the use of supernovae as standard candles. We quantify the impact of this lensing, and discuss ways to overcome the lensing degradation through statistics. In particular, we show that for sufficient numbers of sources, the lensing effects can be well approximated by a Gaussian distribution. We derive an effective variance due to lensing, as a function of source redshift. By observing enough high-redshift sources, the effects of lensing can be mitigated.

1501: WMAP Constraints on the Intra-Cluster Medium

Authors: Niayesh Afshordi, Yen-Ting Lin, and Alastair Sanderson (Harvard University)

I describe an optimized filter match method to extract the thermal SZ signature of a catalog of 116 low-redshift X-ray clusters from the first year data release of the Wilkinson Microwave Anisotropy Probe (WMAP). We detect an over-all amplitude for the SZ signal at the ~ 8-sigma level, yielding a combined constraint of f_{gas}h = 0.08 +/- 0.01 on the gas mass fraction of the Intra-Cluster Medium. We also compile X-ray estimated gas fractions from the literature for our sample, and see that they are consistent with the SZ estimates at the 2-sigma level, while both show an increasing trend with X-ray temperature. Nevertheless, our SZ estimated gas fraction is 30%-40% smaller than the concordance LCDM cosmic average. Based on its spectral and spatial signature, we can also extract the microwave point source signal of the clusters at the 3-sigma level, which puts the average microwave luminosity (at ~ 60 GHz) of bright cluster members (M_K < -21) at (2.4 +/- 0.8) x 10^{27} h^{-2} erg/s/Hz. Furthermore, we can constrain the average dark matter halo concentration parameter to c_{vir}=3.4+0.6-0.9, for clusters with T_x > 5 kev.

1502: Probing Dark Energy with Galaxy Clusters

Authors: Steven W. Allen (Inst. of Astronomy, University of Cambridge/Stanford U./SLAC), Robert Schmidt (Potsdam), Harald Ebeling (U. of Hawaii), Andrew Fabian (U. of Cambridge) Leon van Speybroeck (Harvard-Smithsonian Center for Astrophysics), David Rapetti (U. of Cambridge/Barcelona) Jochen Weller (Fermilab)

I will present the latest results on the mean matter density, dark energy density and dark energy equation of state from Chandra measurements of the X-ray gas mass fraction in the largest, dynamically relaxed galaxy clusters. This method, like supernovae studies, measures the acceleration of the Universe directly and leads to similar, though entirely independent, constraints. I will highlight the complementary nature of X-ray, supernovae and cosmic microwave background studies and show how the combination of these data sets already leads to interesting constraints on the evolution of dark energy, without imposing additional, prior constraints. Future X-ray studies should play a central role in revealing the origin of cosmic acceleration.

1503: Galaxy Clusters and Dark Matter Properties

Authors: John S. Arabadjis (MIT) and M. W. Bautz (MIT)

Laboratory experiments, large-scale computer simulations and observational cosmology have begun to make progress in the campaign to identify the particle responsible for gravitationally-inferred dark matter. We report results from an astrophysical program to measure dark matter particle properties. We use a sample of carefully-selected, highly-relaxed galaxy clusters to constrain the cross section for dark matter elastic self-scattering. We also estimate the gamma ray flux expected from the derived density profile for MSSM neutralino dark matter over a range of velocity-weighted annihiliation cross section.

1504: Selection Functions for SZ Cluster Surveys

Authors: James G. Bartlett, Jean-Baptiste Melin, Jacques Delabrouille (Astroparticule et Cosmologie - Univ. Paris 7)

Sunyaev-Zel'dovich (SZ) surveys for galaxy clusters promise large numbers of clusters at redshifts near or beyond unity. These surveys will vastly increase the redshift range accessible for cluster evolution studies, and they will produce important constraints on dark energy. Correct interpretation of the surveys will require, as for any Astronomical survey, a clear understanding of their selection functions. We discuss the selection function of future SZ observations, showing in particular that ground--based surveys will not be purely flux (Y) limited. Using simulations, we illustrate the importance of selection functions to cosmological constraints and detail the various astrophysical and observational influences on SZ selection functions.

1505: Measurements of Cluster Scaling Relations using the Sunyaev-Zel'dovich Effect

Authors: Sarah Church (stanford University) Bradford Benson (University of California, Berkeley), Keith Thompson (Stanford University)

Mapping the Sunyaev-Zel'dovich (SZ) effect over large areas of sky is a powerful way to detect clusters of galaxies. Future SZ cluster surveys will probe the growth of large-scale structure and so have the potential to determine the dark energy equation of state parameters. The accuracy with which this can be accomplished will depend on how well the relationship between SZ flux and cluster mass is understood. We have used data from SuZIE II (the second incarnation of the Sunyaev-Zel'dovich Infrared Experiment) to investigate scaling relations between integrated SZ flux and X-ray temperature, since the latter is already believed to be a good mass indicator. We find that there is a strong correlation between these two quantities, with the slope of the relationship being consistent with that expected from self-similar cluster evolution.

1506: Intermediate Strength Gravitational Lensing

Authors: John Irwin and Marina Shmakova (SLAC)

Small impact-parameter lensing, sometimes referred to as galaxy-galaxy lensing, can produce observable sextupole and quadrupole moments in background galaxy images. The minima of these moments are aligned in such a way as to give the image a slightly curved shape. We have examined the background galaxies in the Hubble Deep Fields, sorting galaxies by their curvature according to this criteria and have found the curved galaxies to be spatially correlated. Taken as an indication of small impact-parameter lensing, this would suggest the presence of dark matter distributions with 10^12 M_solar dark matter ensembles containing a 100 10^10 M_solar dark matter clumps. In an effort to rule out alternative causes, such as instrument point-spread-function we have fit each image to a model system, which includes a parameterized symmetric background galaxy, a lensing map, distortion by the position-specific point-spread function of the Hubble, the diffusion of the camera, and finally “drizzling” onto the HDF pixels.

1507: Constraints on Dark Energy from Cosmic Complementarity and Weak Lensing Tomography

Authors: Mustapha Ishak (Princeton University)

I will present our constraints on the dark energy parameters from combined available data sets. Next, I will summarize our recent results from an extensive study of projected constraints on dark energy. The study includes results from simulations of several ongoing and future CMB, Supernovae and Weak Lensing surveys with tomographic bins. The dark energy is parameterized using its density and also two variants of its equation of state.

1508: Strong Gravitational Lensing in the Wide Field Era

Authors: Phil Marshall (KIPAC), Roger Blandford (KIPAC), Masao Sako (KIPAC)

To date, systematic searches for gravitational lenses have been limited by our inability to survey large areas of sky to the necessary depth with the required angular resolution: the proposed space telescope SNAP and the ground based Large Synoptic Survey Telescope (LSST) will change this. With the high angular resolution and 9-filter photometry of SNAP complemented by the half-sky coverage and several day cadence of LSST, we highlight some gravitational lensing science enabled by both telescopes in this eagerly anticipated wide field era.

1509: Cosmological Constraints from 2D SZ Catalogs

Authors: Simona Mei (John Hopkins University), J.G. Bartlett (College de France, Universite Paris 7)

We discuss cosmological constraints from two-dimensional catalogs of galaxy clusters observed by the Sunyaev-Zel'dovich (SZ) effect. Three kinds of SZ survey are considered: the almost all-sky Planck survey and two deeper ground-based surveys, one with 10% sky coverage, the other one with a coverage of 250 square degrees.

1510: The ACS Virgo Cluster Survey

Authors: Simona Mei (John Hopkins University) and the ACS VCS team

The Advanced Camera for Surveys (ACS) Virgo Cluster Survey is a program to observe images of 100 early-type galaxies in the Virgo cluster, in the F475W and F850LP bandpasses (SDSS g and z). The primary goals of this survey are the study of the central regions of the program galaxies, their globular cluster systems, and the three-dimensional structure of the Virgo cluster. We summarize the details of this unprecedent dataset and present preliminary results from our ongoing work. Preliminary results are presented.

1511: The ACS Intermediate Cluster Survey:Cluster Evolution at z~1

Authors: Simona Mei (John Hopkins University) and the ACS Intermediate Cluster Survey team

As part of the Advanced Camera for Surveys (ACS) GTO Science programs, the Intermediate Redshift Cluster Survey comprehends ACS observations of a sample of galaxy clusters selected in the optical or X-rays in the redshift range between 0.8 and 1.3. Recent results from this surveys will be discussed, with particular emphasis given to color-magnitude diagrams in that redshift range.

1512: Constraining Dark Energy with X-ray Galaxy Clusters, Supernovae and the Cosmic Microwave Background

Authors: David Rapetti, Steven W. Allen (Institute of Astronomy, Cambridge), Jochen Weller (Fermilab)

We present new constraints on the evolution of dark energy from an analysis of CMB, SNe Ia and X-ray clusters data. Our analysis employs a minimum of priors and exploits the complementary nature of these data sets. We examine a series of dark energy models with up to three free parameters: the current w_0 and the early time w_et dark energy equation of state (EoS) and the scale factor at transition, a_t. From the combined analysis, assuming a constant EoS and that the Universe is flat, we measure w_0=-1.05+0.10-0.12. Including w_et as a free parameter and allowing a_t to vary over the range 0.5< a_t < 0.95 where the data has discriminating power, we measure w_0=-1.27+0.33-0.39 and w_et=-0.66+0.44-0.62. The complementary nature of these data sets also allows us to drop the prior on the curvature. For non-flat models with a constant EoS, we measure w_0=-1.09+0.12-0.15, Omega_m=0.31+-0.04 and obtain a tight constraint on the current dark energy density Omega_de=0.70+-0.03.

1513: A Systematic Search For Gravitationally-Lensed Arcs in the HST/WFPC Archive

Authors: David Sand , T. Treu, R.S. Ellis, G.P. Smith (California Institute of Technology)

We present the results of a systematic search for gravitationally-lensed arcs in clusters located in the HST WFPC2 data archive. By carefully examining the images of 129 clusters we locate 13 candidate radial arcs and 104 tangential arcs whose length/width exceeds 7. We examine the practicality of using the relative fraction of radial to tangential gravitational arcs to statistically constrain the form of the dark matter distribution in cluster cores. We find that the observed arc fraction is consistent with a wide range of density profiles (including those as steep as predicted by CDM) depending on the mass of the assumed brightest cluster galaxy mass component.

1514: Illuminating Dark Energy with Cosmic Shear

Authors: Fergus Simpson (Institute of Astronomy, Cambridge) & Sarah Bridle (University College London)

One of the principal goals of modern cosmology is to constrain the properties of dark energy. The key result of a survey will be the equation of state, assumed constant due to our poor understanding of its behaviour (and since higher parameterisations lead to unwieldy errors). However it is painfully apparent from the myriad of dark energy theories that such an approach may be quite inappropriate. This raises the question - how does our "best-fit" w relate to the true function, w(z)? Saini, Padmanabhan, & Bridle (2003) have already demonstrated that the value of w attained by a supernovae study is well described by a weighted integral over the true function. Adopting a similar approach, we find the corresponding "weight functions" for cosmic shear surveys.

1515: Solving the Cooling Flow Problem of Galaxy Clustersby Dark Matter Neutralino Annihilation

Authors: Tomonori Totani (Kyoto University)

Recent X-ray observations revealed that strong cooling flow of intracluster gas is not present in galaxy clusters, even though predicted theoretically if there is no additional heating source. I show that relativistic particles produced by dark matter neutralino annihilation in cluster cores provide a sufficient heating source to suppress the cooling flow, under reasonable astrophysical circumstances including steepening of the density cusps by SMBH formation, with appropriate particle physics parameters for dark matter neutralinos. In contrast to other astrophysical heat sources such as AGNs, this process is a steady and stable feedback over cosmological time scales after turned on. Observed bubbles in centers of cooling clusters could be formed by relativistic annihilation products.

1516: Constraining Cosmological Parameters with Galaxy Cluster Surveys

Authors: Sheng Wang (Columbia University/Brookhaven), Justin Khoury, Zoltan Haiman (Columbia University), Morgan May (Brookhaven)

Future surveys will yield thousands of galaxy clusters and can place precise statistical constraints on cosmological parameters. We use a Fisher matrix approach to quantify constraints in forthcoming surveys that will identify clusters by their X-ray emission, Sunyaev-Zeldovich effect, or weak lensing shear. We simultaneously include non-cosmological parameters in our analysis, which express uncertainties in the mass-observable relations. We find that by combining observables, such as the abundance evolution (dN/dz) and the spatial power spectrum (P(k)), degeneracies (both among cosmological parameters, and between cosmological and non-cosmological parameters) can be broken, and tight constraints can be obtained on (1) the evolution of the dark energy equation of state dw/dz and on (2) the mass of neutrinos. Combining cluster data with CMB anisotropy measurements by Planck further breaks degeneracies and tightens contstriants.

1517: Isolating Geometry in Weak Lensing Measurements

Authors: Jun Zhang(Fermilab/Columbia Univ.), Lam Hui(Fermilab/Columbia Univ./Univ. of Chicago), Albert Stebbins(Fermilab/Univ. of Chicago)

In weak lensing measurements, given a foreground galaxy-density field or shear field, the galaxy-shear and shear-shear correlations have a unique scaling relation with the source redshift. Such a relation can be exploited to measure the geometrical distances without assuming anything on the structure formation model(e.g. CDM). It works like another standard candle for constraining the cosmological parameters! Furthermore, with this method, the intrinsic allignment can be separated from the shear-shear correlation because it does not have the same scaling relation.

1518: On the Energy Output of X-ray Emitting Electrons in the Galactic Disk and Clusters of Galaxies

Authors: Vladimir A.Dogiel (P. N. Lebedev Institute)

We analyze processes for the hard X-ray emission from the Galactic disk and clusters of galaxies, whose origin has remained enigmatic for many years. Up to now no model has been able to explain the physical origin of this emission. The model of bremsstrahlung radiation often used for interpretation requires an energy output in emitting particles higher than the luminosity provided by known sources. We show that this energy enigma can be resolved if the emission comes directly from regions of particle acceleration. In this case a broad quasi-thermal transition region of particle excess is formed between the thermal and nonthermal energy regions. Then the necessary energy output for production of quasi-thermal electrons emitting X-rays can definitely be supplied known of energy.

1519: Soft Excess Emission from Clusters of Galaxies: the First Ten Years Since its Discovery

Authors: Richard Lieu (University of Alabama, Huntsville)

The cluster soft excess phenomenon is reviewed with emphasis on XMM Newton, which confirmed the existence of this emission component for the original `discovery' sample of clusters, and found even stronger signals from several new clusters. For the outer radii, the thermal origin as warm infalling gas with large mass implications is still the most promising interpretation, despite doubts over the OVII line detections. For the inner radii, the soft excess is very bright in its absolute flux - here the only viable scenario is the inverse- Compton interaction between relativistic intracluster electrons and the cosmic microwave background. This review summarizes the current status of data analysis and theoretical development, including results from the first cosmological hydrodynamic simulation which successfully reproduced in detail the observational characteristics of the outersoft excess, as thermal radiation from the cluster merger process.

1520: An XMM-Newton Observation of Abell 2597

Authors: R. Glenn Morris, Andrew C. Fabian (Institute of Astronomy, Cambridge)

We present results from a long XMM observation of the galaxy cluster A2597. EPIC fits to the central region, as well as broad-band fits to the RGS spectra, are consistent with a cooling flow of around 100 solar masses per year; with a preferred low-temperature cut-off of essentially zero. Similar results are obtained from the Chandra data. We report weak detections of the important emission lines from iron XVII at 15, 17 angstrom rest wavelength, characteristic of temperatures ~0.3 keV. A simple line-flux to mass-deposition rate conversion also leads to values ~100 solar masses per year. These mass deposition rates, whilst lower than those of previous generations of X-ray observatories, are consistent with those obtained from UV data for this object. This raises the intriguing possibility of a classical cooling flow, cooling from 4 keV by more than two orders of magnitude in temperature.

1521: A Non-Parametric Method for Galaxy Cluster Modeling

Authors: J. R. Peterson (KIPAC/Stanford), K. Andersson (SLAC), P. Marshall (KIPAC/Stanford)

We present a new method for analyzing X-ray data from clusters of galaxies. The method uses hundreds of X-ray emitting plasma "blobs". Each blob is assigned its own temperature, abundances, position, luminosity, and size. The X-ray data for this complex model is generated by Monte Carlo simulations for both XMM-Newton RGS and EPIC data. Iterations of blob parameters are performed using Markov chains and a complete set of statistical realizations that are consistent with the observations are obtained. We apply the method to RGS observations of Perseus and M87. This approach demonstrates in a model-independent context the failure of the cooling flow model and places detailed spatially-resolved emission measure constraints on cooling flow models. We also present EPIC results of Abell 1689 using this approach. We expect that these techniques will lead to an easier comparison of X-ray results with those of weak/strong lensing and SZ observations in future studies.

1601: Periodic Variability and Binary Black Hole Systems in Blazars

Authors: Frank M. Rieger (National University of Ireland)

We consider the periodic modulation of emission from jets in blazar-type sources. A differential Doppler boosting origin, associated with the helical motion of a radiating component, is analyzed for different periodic driving sources including orbital motion and jet precession in a binary black hole system (BBHS). We emphasize that for non-ballistic helical motion classical travel time effects can lead to strong shortening effects, such that the observed period may be roughly a "bulk Lorentz factor to the square" smaller than the underlying driving period. The relevance of the above noted scenarios will be discussed for the BL Lac object AO 0235+16.

1602: Observations of the Galactic Centre Region with H.E.S.S.

Authors: Jim Hinton, Werner Hofmann, Stefan Funk, Wystan Benbow, Loic Rolland and Mathieu de Naurois for the H.E.S.S. Collaboration

H.E.S.S. is an array of imaging Cherenkov telescopes designed for high sensitivity measurements of astrophysical gamma ray sources in the 100 GeV to 10 TeV regime. Its southern hemisphere location (in the Khomas Highlands of Namibia) makes it an ideal instrument for the study of the complex region close to the centre of our galaxy. Observations of the galactic centre region have been made with H.E.S.S. during 2003(with two telescopes) and 2004 (with the full four telescope array). The unprecedented angular resolution and pointing precision of H.E.S.S. have allowed us to make the most precise measurements so far of the very high energy signal from the galactic centre.

1603: The New Type of Spiral Density Wave in Cool Accretion Disks

Authors: Dmitry V. Bisikalo (Institute of Astronomy, Russian Academy of Sciences)

Possible changes in the disk structure after transition from solutions with high gas temperature to those with cool gas are discussed. The existence of the new type of spiral density waves in inner gasdynamically undisturbed parts of the disk is proposed. The finding of the new "precession" type of spiral waves in cool disk is confirmed by results of 3D gasdynamic modeling. The mechanism of the formation of this wave, its parameters, and possible observational evidences are considered. It is shown to be possible to explain superoutbursts and superhumps in stars of SU UMa type by the formation of the "precession" spiral wave in the accretion disk.

1604: The Main Event: High Resolution Radio Imaging of Sagittarius A*

Authors: Geoffrey C. Bower (University of California, Berkeley)

The compact radio source in the Galactic Center provides the best opportunity to image the environment of a black hole on the scale of the event horizon. We describe recent very long baseline interferometric measurements which for the first time conclusively measure the size of the radio emitting region. The size is 24 +/- 2 Schwarzschild radii at a wavelength of 7mm. We also describe future measurements that test the effects of gravitational lensing on a scale of a few Schwarzschild radii.

1605: Relativistic Jets Accelerated from the Disk Coronas in Active Galactic Nuclei

Authors: Xinwu Cao(Shanghai Astronomical Observatory, CAS)

We calculate the maximal jet power extractable from a rapidly spinning black hole or the accretion disk (standard thin disk or advection dominated accretion flow, ADAF) surrounding the black hole. Compared the theoretical calculations with the observational data, ADAFs are required to be present in the inner regions of the disks and transit to standard thin disks at radii of ~40-150~GM_{bh}/c^2 for BL Lac objects. For some radio quasars, their relativistic jets are too powerful to be extracted from the standard thin accretion disks or rapidly spinning black holes surrounded by standard thin disks. If the ADAFs are present in these quasars, their bright optical continuum luminosity cannot be produced by pure-ADAFs due to their low accretion rates and low radiation efficiency, unless the dimensionless accretion rates \dot{m}=\dot{M}/\dot{M}_{Edd} can be as high as \ga 0.05 and the ADAFs transit to standard thin disks at rather small radii of ~20GM_{bh}/c^2. We propose that the disk-corona structure is present at least in some radio quasars. The plasmas in the corona are very hot, and the scale-height of the corona H_c ~ R. Powerful jets with Q_{jet} ~ L_{bol} (bolometric luminosity) can form by the large-scale magnetic fields created by dynamo processes in the disk coronas of some radio quasars.

1607: Hydrodinamical Scaling Laws for Astrophysical Jets

Authors: Martin Huarte, Sergio Mendoza (Instituto de Astronomia (IAUNAM))

The idea of a unified model for all astrophysical jets has been considered for some time. We present some hydrodinamical scaling laws relevant for all type of astrophysical jets. These scaling relations apply quite well to the jets associated with gamma-ray bursts, Herbig-Haro objecs, micro quasars and quasars in general.

1608: Kinematics of Relativistic Kpc-scale Quasar Jets

Authors: Herman Marshall (Massachusetts Institute of Technology)

There are several very good examples of straight quasar jets where the angle to the line of sight can be inferred from observations of apparent superluminal motion. We use the X-ray and radio observations of a few cases that are spatially resolved along the jets to determine the jet speed under the assumption that the X-ray emission results from inverse Compton scattering of cosmic microwave background photons. The results can then be used to determine the kinetic energy losses under various assumptions about the jet matter content.

1609: Hydrodynamic Turbulence in Accretion Disks

Authors: Banibrata Mukhopadhyay, Niayesh Afshordi, Ramesh Narayan (Harvard-Smithsonian Center for Astrophysics)

Turbulent viscosity in cold accretion disks is likely to be hydrodynamic in origin. We investigate the growth of hydrodynamic perturbations in a small region of a disk, modeled as a linear shear flow with Coriolis force between two parallel walls. Although there are no exponentially growing eigenmodes in this system, because of the non-normal nature of the modes, it is possible to have a large transient growth in the energy of certain perturbations. For a constant angular momentum disk, the energy grows by more than a factor of 1000 for a Reynolds number of only 1000, and so turbulence is easily excited. For a Keplerian disk, the growth is more modest, and energy growth by a factor of 1000 requires a Reynolds number of almost a million. However, accretion disks have even larger Reynolds numbers. Therefore, transient growth of perturbations could seed turbulence in such disks.

1610: Three-Dimensional PIC Simulation of Astrophysical Jets in Plasmas

Authors: Johnny S.T. Ng, Robert Noble (SLAC)

Relativistic outflow of bulk material extending up to millions of light years have been observed in high energy astrophysical objects such as AGN's. Issues and questions that motivated our work are: what are the key jet-plasma physics and scalings that determine jet stability, break-up, particle acceleration, and radiation signatures? What are the parameters for scaled laboratory experiments that explore this physics, benchmark the codes, and connect this plasma physics to the astrophysical observations? We have adopted the TRISTAN code in our jet dynamics simulations. In this paper, we present our preliminary findings and plans for future work.

1611: On The Magnetic Field In Quasar And FR II Large-Scale Jets

Authors: L. Stawarz (Obserwatorium Astronomiczne UJ), Jun Kataoka (Tokyo Institute of Technology)

Here we report systematic comparison of the spectral properties of large-scale jets, hotspots and extended lobes in quasars and FR II radio galaxies recently observed with Chandra and ASCA. We argue, that if the strong X-ray emission of the jet knots in these objects results from comptonisation of the CMB photons, as usually considered, the powerful large-scale jets are most likely far from the minimum-power condition in a sence that the magnetic field thereby is below equipartition. We also show that the X-ray emission of the hot-spots and lobes in the compiled dataset agrees with the minimum-power condition. In this context, we we point out on the need for the substantial amplification of the magnetic field within the terminal shocks of powerful large-scale jets of quasars and FR II sources.

1612: On the Magnetic Field in Kiloparsec-Scale Jets of FR I Radio Galaxies

Authors: L. Stawarz (Obserwatorium Astronomiczne UJ), A. Siemiginowska (Harvard-Smithsonian Center for Astrophysics), M. Ostrowski (Obserwatorium Astronomiczne UJ), M. Sikora (Centrum Astronomiczne Im. M. Kopernika)

Energy content of large-scale jets in FR I radio galaxies is still an open issue. Here we show, that upper limits on the high-energy gamma-ray emission of the kpc-scale jet in M87 radio galaxy imposed by EGRET and Whipple observations provide important constraints on the magnetic field strength in this object. In particular, a non-detection of gamma-ray radiation from knot A expected from the inverse Compton scattering of the starlight photons by the synchrotron-emitting jet electrons, implies that the magnetic field thereby cannot be smaller than the equipartition value. In this context, we point out a potential need for a substantial amplification of the magnetic field along the jet, from sub-pc to kpc scales in FR I jets, suggesting a turbulent dynamo as a plausible process responsible for the aforemention amplification.

1613: Large-Scale Radio and X-ray Jets in the Highest Redshift Quasars

Authors: C. C. Cheung (NRAO & MIT), Nicholas Lee, John F. C. Wardle (Brandeis)

We describe our program to search for and study the kilo-parsec scale radio jets in a sample of high-redshift (greater than 3.4), flat spectrum quasars. To date, we have radio spectral and structural information on five such jets (one previously unknown) from archival and new VLA data. Two of these quasars have been imaged with Chandra, and four with the HST, and our analysis of these data will also be presented. We have recently acquired new VLA data for 19 high-redshift quasars with no previously known extended arcsecond-scale radio emission, in order to search for radio jets -- we will include results from these observations. These high-redshift sources are important targets for testing current X-ray jet emission models and follow-up multi-wavelength observations will shed light on this problem.