## [0810.5262] Fall of Elastic Bar in Central Gravitational Field: I. Newtonian Gravity

Authors: Sergey S. Kokarev

Date: 29 Oct 2008

Abstract: Within some reasonable approximations we calculate deformation of an elastic bar, falling on the source of central gravitational field. We consider both elastic deformations and plastic flow together with destroying of the bar. Concrete calculations for a number of materials are presented.

#### Oct 30, 2008

0810.5262 (/preprints)
2008-10-30, 08:39 

## [0810.5336] Higher-order spin effects in the amplitude and phase of gravitational waveforms emitted by inspiraling compact binaries: Ready-to-use gravitational waveforms

Authors: K.G. Arun, Alessandra Buonanno, Guillaume Faye, Evan Ochsner

Date: 29 Oct 2008

Abstract: We provide ready-to-use time-domain gravitational waveforms for spinning compact binaries with precession effects through 1.5PN order in amplitude and compute their mode decomposition using spin-weighted -2 spherical harmonics. In the presence of precession, the gravitational-wave modes (l,m) contain harmonics originating from combinations of the orbital frequency and precession frequencies. We find that the gravitational radiation from binary systems with large mass asymmetry and large inclination angle can be distributed among several modes. For example, during the last stages of inspiral, for some maximally spinning configurations, the amplitude of the (2,0) and (2,1) modes can be comparable to the amplitude of the (2,2) mode. If the mass ratio is not too extreme, the l=3 and l=4 modes are generally one or two orders of magnitude smaller than the l = 2 modes. Restricting ourselves to spinning, non-precessing compact binaries, we apply the stationary-phase approximation and derive the frequency-domain gravitational waveforms including spin-orbit and spin(1)- spin(2) effects through 1.5PN and 2PN order respectively in amplitude, and 2.5PN order in phase. Since spin effects in the amplitude through 2PN order affect only the first and second harmonics of the orbital phase, they do not extend the mass reach of gravitational-wave detectors. However, they can interfere with other harmonics and lower or raise the signal-to-noise ratio depending on the spin orientation. These ready-to-use waveforms could be employed in the data-analysis of the spinning, inspiraling binaries as well as in comparison studies at the interface between analytical and numerical relativity.

#### Oct 29, 2008

0810.5336 (/preprints)
2008-10-29, 18:56 

## [0810.5255] Is the black hole area theorem always classically valid?

Authors: Christopher Eling, Jacob D. Bekenstein

Date: 29 Oct 2008

Abstract: Hawking's area theorem guarantees the monotonic growth of the surface area of any black hole provided the matter and fields interacting with it respect the weak positive energy condition. The theorem does not identify specific effects which make it work in particular situations. We here report a specific gedanken experiment in which the theorem seems to be violated: the dropping of an electrically charged test object from rest at a point close to the horizon and on the symmetry axis of a nearly extreme Kerr black hole. In the parallel experiment involving a magnetically charged Reissner-Nordstrom hole, the analogous violation is defused by taking into account a subtle source of repulsion of the charge: the spinning up of the black hole in the process of bringing the charge down to its dropping point. No such effect is known for the Kerr case; we find the electric self-force of the charge to be insufficient to right matters. After exhaustive analysis of the problem we conclude that some, as yet unknown, classical effect must be responsible for the enforcement of the area theorem.

#### Oct 29, 2008

0810.5255 (/preprints)
2008-10-29, 18:56 

## [0810.4848] Determination of the neutron star mass-radii relation using narrow-band gravitational wave detector

Authors: C.H. Lenzi, M. Malheiro, R. M. Marinho, C. Provid&#xea;ncia, G. F. Marranghello

Date: 27 Oct 2008

Abstract: The direct detection of gravitational waves will provide valuable astrophysical information about many celestial objects. The most promising sources of gravitational waves are neutron stars and black holes. These objects emit waves in a very wide spectrum of frequencies determined by their quasi-normal modes oscillations. In this work we are concerned with the information we can extract from f and p$_I$-modes when a candidate leaves its signature in the resonant mass detectors ALLEGRO, EXPLORER, NAUTILUS, MiniGrail and SCHENBERG. Using the empirical equations, that relate the gravitational wave frequency and damping time with the mass and radii of the source, we have calculated the radii of the stars for a given interval of masses $M$ in the range of frequencies that include the bandwidth of all resonant mass detectors. With these values we obtain diagrams of mass-radii for different frequencies that allowed to determine the better candidates to future detection taking in account the compactness of the source. Finally, to determine which the models of compact stars emit gravitational waves in the frequency band of the mass resonant detectors, we compare the mass-radii diagrams obtained by different neutron stars sequences from several relativistic hadronic equations of state (GM1, GM3, TM1, NL3) and quark matter equations of state (NJL, MTI bag model). We verify that quark stars obtained from MIT bag model with bag constant equal to 170 MeV and quark of matter in color-superconductivity phase are the best candidates for mass resonant detectors.

#### Oct 29, 2008

0810.4848 (/preprints)
2008-10-29, 18:54 

## [0810.4735] High-velocity collision of two black holes

Authors: Masaru Shibata, Hirotada Okawa, Tetsuro Yamamoto

Date: 27 Oct 2008

Abstract: We study nonaxisymmetric collision of two black holes (BHs) with a high velocity $v=|dxˆi/dxˆ0|=0.6$--$0.9c$ at infinity, where $xˆ{\mu}$ denotes four-dimensional coordinates. We prepare two boosted BHs for the initial condition which is different from that computed by a simple moving-puncture approach. By extrapolation of the numerical results, we find that the impact parameter has to be smaller that $\approx 2.5GM_0/cˆ2$ for formation of a BH in the collision for $v \to c$, where $M_0 cˆ2$ is the initial total ADM mass energy of the system. For the critical value of the impact parameter, 20--30% of mass energy and 60--70% of angular momentum are dissipated by gravitational radiation for $v=0.6$--$0.9c$.

#### Oct 29, 2008

0810.4735 (/preprints)
2008-10-29, 18:54 

## [0810.4886] Black Holes, AdS, and CFTs

Authors: Donald Marolf

Date: 27 Oct 2008

Abstract: This brief conference proceeding attempts to explain the implications of the anti-de Sitter/conformal field theory (AdS/CFT) correspondence for black hole entropy in a language accessible to relativists and other non-string theorists. The main conclusion is that the Bekenstein-Hawking entropy S_{BH} is the density of states associated with certain superselections sectors, defined by what may be called the algebra of boundary observables. Interestingly while there is a valid context in which this result can be restated as "S_{BH} counts all states inside the black hole," there may also be another in which it may be restated as "$S_{BH}$ does not count all states inside the black hole, but only those that are distinguishable from the outside." The arguments and conclusions represent the author's translation of the community's collective wisdom, combined with a few recent results. For the proceedings of the WE-Heraeus-Seminar: Quantum Gravity: Challenges and Perspectives, dedicated to the memory of John A. Wheeler.

#### Oct 29, 2008

0810.4886 (/preprints)
2008-10-29, 18:53 

## [0810.4529] The response of interferometric gravitational wave detectors

Authors: Lee Samuel Finn

Date: 24 Oct 2008

Abstract: The standard derivation of the response of interferometric gravitational wave detectors makes a series of erroneous approximations regarding the coordinate trajectory of the light and the parameterization of the null geodesic it travels along. These errors appear to have remained unrecognized for at least thirty five years. We provide, in full detail, a correct derivation of the response of a single-bounce Michelson interferometer to gravitational waves, compare it to the "standard", but incorrect, derivation, and show where the earlier mistakes were made. By a fortuitous set of circumstances, not generally so, the final result is the same.

#### Oct 29, 2008

0810.4529 (/preprints)
2008-10-29, 18:53 

## [0706.2286] Spectral Methods for Numerical Relativity

Authors: Philippe Grandclement (LUTH), J&#xe9;r&#xf4;me Novak (LUTH)

Date: 15 Jun 2007

Abstract: Equations arising in General Relativity are usually too complicated to be solved analytically and one has to rely on numerical methods to solve sets of coupled partial differential equations. Among the possible choices, this paper focuses on a class called spectral methods where, typically, the various functions are expanded onto sets of orthogonal polynomials or functions. A theoretical introduction on spectral expansion is first given and a particular emphasis is put on the fast convergence of the spectral approximation. We present then different approaches to solve partial differential equations, first limiting ourselves to the one-dimensional case, with one or several domains. Generalization to more dimensions is then discussed. In particular, the case of time evolutions is carefully studied and the stability of such evolutions investigated. One then turns to results obtained by various groups in the field of General Relativity by means of spectral methods. First, works which do not involve explicit time-evolutions are discussed, going from rapidly rotating strange stars to the computation of binary black holes initial data. Finally, the evolutions of various systems of astrophysical interest are presented, from supernovae core collapse to binary black hole mergers.

#### Oct 29, 2008

0706.2286 (/preprints)
2008-10-29, 18:52 

## [0810.4246] A simple derivation of the electromagnetic field of an arbitrarily moving charge

Date: 23 Oct 2008

Abstract: The expression for the electromagnetic field of a charge moving along an arbitrary trajectory is obtained in a direct, elegant, and Lorentz invariant manner without resorting to more complicated procedures such as differentiation of the Lienard-Wiechert potentials. The derivation uses arguments based on Lorentz invariance and a physically transparent expression originally due to J.J.Thomson for the field of a charge that experiences an impulsive acceleration.

#### Oct 29, 2008

0810.4246 (/preprints)
2008-10-29, 18:52 

## [0810.3759] SN1987A: Revisiting the Data and the Correlation between Neutrino and Gravitational Detectors

Authors: P. Galeotti, G. V. Pallottino, G. Pizzella

Date: 21 Oct 2008

Abstract: We re-examine the data taken by the neutrino detectors during the supernova SN1987A. It is found that the Kamiokande data, in addition to the well known burst at 7:35 hours UT, show another one at 7:54 hours, with seven pulses in 6.2 seconds. This second burst supports the idea that the duration of the collapse was much longer than a few seconds, as already suggested by the LSD detection at 2:56 hours the same day, i.e. four and a half hours earlier. The correlations between the gravitational wave detectors (Rome and Maryland) and the neutrino detectors are also revisited. It is shown that the g.w. detectors exhibit significant correlations with both the LSD and the Kamiokande detectors over periods of one-two hours that are centered, in both cases, at the LSD time.

#### Oct 29, 2008

0810.3759 (/preprints)
2008-10-29, 18:51 

## [0711.3046] The gravitational wave signal of the short rise fling of galactic run away pulsars

Authors: Herman J. Mosquera Cuesta, Carlos A. Bonilla Quintero

Date: 20 Nov 2007

Abstract: Determination of pulsar parallaxes and proper motions addresses fundamental astrophysical open issues. Here, the ATNF Catalog is scrutinized searching for pulsar distances and proper motions. For a sample of 212 run away pulsars (RAPs), which currently run across the Galaxy at very high speed and undergo large displacements, some gravitational-wave (GW) signals produced by such present accelerations appear to be detectable after calibration against the Advanced LIGO (LIGO II). Motivated by this insight, we address the issue of the pulsar kick at birth. We show that during the short rise fling each run away pulsar (RAP) generates a GW signal with characteristic amplitude and frequency that makes it detectable by current GW interferometers. For a realistic analysis, an efficiency parameter is introduced to quantify the expenditure of the rise fling kinetic energy, which is estimated from the linear momentum conservation law applied to the supernova explosion that kicks out the pulsar. The remaining energy is supposed to be used to make the star to spin. Thus, a comparison with the spin of ATNF pulsars having velocity in the interval 400-500 km s$ˆ{-1}$ is performed. The resulting difference suggests that other mechanisms should dissipate part of that energy to produce the observed pulsar spin periods. Meanwhile, the kick phenomenon may also occur in globular and open star clusters at the formation or disruption of very short period compact binary systems wherein abrupt velocity and acceleration similar to those given to RAPs during the short rise fling can be imparted to each orbital partner. Thus pulsar astrometry from micro- to nano-arsec scales might be of much help. In case of a supernova, the RAP GW signal could be a benchmark for the GW signal from the core collapse.

#### Oct 29, 2008

0711.3046 (/preprints)
2008-10-29, 18:49 

## [0810.2602] f(R) gravity: successes and challenges

Authors: Valerio Faraoni (Bishop&#x27;s University)

Date: 15 Oct 2008

Abstract: We review the state of the art of f(R) theories of gravity (in their various formulations), which have been proposed as an explanation of the cosmic acceleration alternative to dark energy. The successes of f(R) gravity are discussed, together with the challenges imposed by minimal criteria for their viability.

#### Oct 29, 2008

0810.2602 (/preprints)
2008-10-29, 18:48 

## [0810.2530] Two approaches for the gravitational self force in black hole spacetime: Comparison of numerical results

Authors: Norichika Sago, Leor Barack, Steven Detweiler

Date: 14 Oct 2008

Abstract: Recently, two independent calculations have been presented of finite-mass ("self-force") effects on the orbit of a point mass around a Schwarzschild black hole. While both computations are based on the standard mode-sum method, they differ in several technical aspects, which makes comparison between their results difficult--but also interesting. Barack and Sago [Phys. Rev. D {\bf 75}, 064021 (2007)] invoke the notion of a self-accelerated motion in a background spacetime, and perform a direct calculation of the local self force in the Lorenz gauge (using numerical evolution of the perturbation equations in the time domain); Detweiler [Phys. Rev. D {\bf 77}, 124026 (2008)] describes the motion in terms a geodesic orbit of a (smooth) perturbed spacetime, and calculates the metric perturbation in the Regge--Wheeler gauge (using frequency-domain numerical analysis). Here we establish a formal correspondence between the two analyses, and demonstrate the consistency of their numerical results. Specifically, we compare the value of the conservative $O(\mu)$ shift in $uˆt$ (where $\mu$ is the particle's mass and $uˆt$ is the Schwarzschild $t$ component of the particle's four-velocity), suitably mapped between the two orbital descriptions and adjusted for gauge. We find that the two analyses yield the same value for this shift within mere fractional differences of $\sim 10ˆ{-5}$--$10ˆ{-7}$ (depending on the orbital radius)--comparable with the estimated numerical error.

#### Oct 29, 2008

0810.2530 (/preprints)
2008-10-29, 18:47 

## [0810.2264] Gravitational Wave Burst Source Direction Estimation using Time and Amplitude Information

Authors: J. Markowitz, M. Zanolin, L.Cadonati, E. Katsavounidis

Date: 13 Oct 2008

Abstract: In this article we study two problems that arise when using timing and amplitude estimates from a network of interferometers (IFOs) to evaluate the direction of an incident gravitational wave burst (GWB). First, we discuss an angular bias in the least squares timing-based approach that becomes increasingly relevant for moderate to low signal-to-noise ratios. We show how estimates of the arrival time uncertainties in each detector can be used to correct this bias. We also introduce a stand alone parameter estimation algorithm that can improve the arrival time estimation and provide root-sum-squared strain amplitude (hrss) values for each site. In the second part of the paper we discuss how to resolve the directional ambiguity that arises from observations in three non co-located interferometers between the true source location and its mirror image across the plane containing the detectors. We introduce a new, exact relationship among the hrss values at the three sites that, for sufficiently large signal amplitudes, determines the true source direction regardless of whether or not the signal is linearly polarized. Both the algorithm estimating arrival times, arrival time uncertainties, and hrss values and the directional follow-up can be applied to any set of gravitational wave candidates observed in a network of three non co-located interferometers. As a case study we test the methods on simulated waveforms embedded in simulations of the noise of the LIGO and Virgo detectors at design sensitivity.

#### Oct 29, 2008

0810.2264 (/preprints)
2008-10-29, 18:47 

## [0810.1767] High-accuracy waveforms for binary black hole inspiral, merger, and ringdown

Authors: Mark A. Scheel, Michael Boyle, Tony Chu, Lawrence E. Kidder, Keith D. Matthews, Harald P. Pfeiffer

Date: 9 Oct 2008

Abstract: The first spectral numerical simulations of 16 orbits, merger, and ringdown of an equal-mass non-spinning binary black hole system are presented. Gravitational waveforms from these simulations have accumulated numerical phase errors through ringdown of ~0.1 radian when measured from the beginning of the simulation, and ~0.02 radian when waveforms are time and phase shifted to agree at the peak amplitude. The waveform seen by an observer at infinity is determined from waveforms computed at finite radii by an extrapolation process accurate to ~0.01 radian in phase. The phase difference between this waveform at infinity and the waveform measured at a finite radius of r=100M is about half a radian. The ratio of final mass to initial mass is M_f/M = 0.95162 +- 0.00002, and the final black hole spin is S_f/M_fˆ2=0.68646 +- 0.00004.

#### Oct 29, 2008

0810.1767 (/preprints)
2008-10-29, 18:46 

## [0803.1835] Constraints on the Size of Extra Dimensions from the Orbital Evolution of Black-Hole X-Ray Binaries

Authors: Tim Johannsen (Arizona), Dimitrios Psaltis (Arizona), Jeffrey E. McClintock (Harvard)

Date: 13 Mar 2008

Abstract: One of the plausible unification schemes in physics considers the observable universe to be a 4-dimensional surface (the "brane") embedded in a higher-dimensional curved spacetime (the "bulk"). In such braneworld gravity models with infinitely large extra dimensions, black holes evaporate fast through the emission of the additional gravitational degrees of freedom, resulting in lifetimes of stellar-mass black holes that are significantly smaller than the Hubble time. We show that the predicted evaporation rate leads to a change in the orbital period of X-ray binaries harboring black holes that is observable with current instruments. We obtain an upper limit on the rate of change of the orbital period of the binary A0620-00 and use it to constrain the asymptotic curvature radius of the extra dimension to a value comparable to the one obtained by table-top experiments. Furthermore we argue that any measurement of a period increase for low-mass X-ray binaries with a high mass ratio is evidence for new physics beyond general relativity and the standard model.

#### Oct 17, 2008

0803.1835 (/preprints)
2008-10-17, 13:12 

## [0810.1328] Effective Field Theory Calculation of 2PN Binary Dynamics

Authors: James B. Gilmore, Andreas Ross

Date: 8 Oct 2008

Abstract: We use the effective field theory for gravitational bound states, proposed by Goldberger and Rothstein, to compute the interaction Lagrangian of a binary system at the second Post-Newtonian order. Throughout the calculation, we use a metric parametrization based on a temporal Kaluza-Klein decomposition and test the claim by Kol and Smolkin that this parametrization provides important calculational advantages. We demonstrate how to use the effective field theory method efficiently in precision calculations, and we reproduce known results for the second Post-Newtonian order equations of motion in harmonic gauge in a straightforward manner.

#### Oct 09, 2008

0810.1328 (/preprints)
2008-10-09, 08:48 

## [0809.3448] Spinning down newborn neutron stars: nonlinear development of the r-mode instability

Authors: Ruxandra Bondarescu, Saul A. Teukolsky, Ira Wasserman (Cornell University)

Date: 19 Sep 2008

Abstract: We model the nonlinear saturation of the r-mode instability via three-mode couplings and the effects of the instability on the spin evolution of young neutron stars. We include one mode triplet consisting of the r-mode and two near resonant inertial modes that couple to it. The inertial modes are excited when the r-mode amplitude grows above the parametric instability threshold. We start our evolutions with a star of temperature ~ 10ˆ{10} K and a spin frequency close to the Kepler break-up frequency. The evolution of the star is dynamic and initially dominated by fast neutrino cooling. The outcome of the evolution is determined by when the cooling can be stopped by viscous heating. At first, the r-mode is unstable and its amplitude grows exponentially until it either reaches a large enough amplitude to generate a viscous dissipation that balances the cooling or until it reaches the parametric instability threshold amplitude. If thermal equilibrium is reached first, the star starts spinning down and the evolution can be adequately described by a one-mode model. If parametric instability is reached first, two near-resonant inertial modes that couple to the r-mode are excited. The viscous heating due to the three modes balances the neutrino cooling and the mode amplitudes oscillate around quasi-stationary states that can be determined algebraically. In both cases we find that when the r-mode is unstable the evolution of the temperature and the spin of the star can be approximated by trajectories along sequences of quasi-stationary states. Some of these evolutions lead to gravitational radiation that may be detectable by advanced LIGO if fast spinning young neutron stars exist in our galaxy. Such a detection could yield information on internal dissipation in neutron stars.

#### Oct 06, 2008

0809.3448 (/preprints)
2008-10-06, 09:53 

## [0809.4352] Gravitational radiation from pulsar glitches

Authors: C. A. van Eysden, A. Melatos

Date: 25 Sep 2008

Abstract: The nonaxisymmetric Ekman flow excited inside a neutron star following a rotational glitch is calculated analytically including stratification and compressibility. For the largest glitches, the gravitational wave strain produced by the hydrodynamic mass quadrupole moment approaches the sensitivity range of advanced long-baseline interferometers. It is shown that the viscosity, compressibility, and orientation of the star can be inferred in principle from the width and amplitude ratios of the Fourier peaks (at the spin frequency and its first harmonic) observed in the gravitational wave spectrum in the plus and cross polarizations. These transport coefficients constrain the equation of state of bulk nuclear matter, because they depend sensitively on the degree of superfluidity.

#### Oct 06, 2008

0809.4352 (/preprints)
2008-10-06, 09:52 

## [0809.3838] Dynamics of Black Hole Pairs I: Periodic Tables

Authors: Janna Levin, Becky Grossman

Date: 23 Sep 2008

Abstract: Although the orbits of comparable mass, spinning black holes seem to defy simple decoding, we find a means to decipher all such orbits. The dynamics is complicated by extreme perihelion precession compounded by spin-induced precession. We are able to quantitatively define and describe the fully three dimensional motion of comparable mass binaries with one black hole spinning and expose an underlying simplicity. To do so, we untangle the dynamics by capturing the motion in the orbital plane. Our results are twofold: (1) We derive highly simplified equations of motion in a non-orthogonal orbital basis, and (2) we define a complete taxonomy for fully three-dimensional orbits. More than just a naming system, the taxonomy provides unambiguous and quantitative descriptions of the orbits, including a determination of the zoom-whirliness of any given orbit. Through a correspondence with the rationals, we are able to show that zoom-whirl behavior is prevalent in comparable mass binaries in the strong-field regime. A first significant conclusion that can be drawn from this analysis is that all generic orbits in the final stages of inspiral under gravitational radiation losses are characterized by precessing clovers with few leaves and that no orbit will behave like the tightly precessing ellipse of Mercury. The gravitational waveform produced by these low-leaf clovers will reflect the natural harmonics of the orbital basis -- harmonics that, importantly, depend only on radius. The significance for gravitational wave astronomy will depend on the number of windings the pair executes in the strong-field regime and could be more conspicuous for intermediate mass pairs than for stellar mass pairs.

#### Oct 06, 2008

0809.3838 (/preprints)
2008-10-06, 09:51 

## [0809.3412] Gravitational waves from resolvable massive black hole binary systems and observations with Pulsar Timing Arrays

Authors: A. Sesana, A. Vecchio, M. Volonteri

Date: 19 Sep 2008

Abstract: Massive black holes are key components of the assembly and evolution of cosmic structures and a number of surveys are currently on-going or planned to probe the demographics of these objects and to gain insight into the relevant physical processes. Pulsar Timing Arrays (PTAs) currently provide the only means to observe gravitational radiation from massive black hole binary systems with masses >10ˆ7 solar masses. The whole cosmic population produces a stochastic background that could be detectable with upcoming Pulsar Timing Arrays. Sources sufficiently close and/or massive generate gravitational radiation that significantly exceeds the level of the background and could be individually resolved. We consider a wide range of massive black hole binary assembly scenarios, we investigate the distribution of the main physical parameters of the sources, such as masses and redshift, and explore the consequences for Pulsar Timing Arrays observations. Depending on the specific massive black hole population model, we estimate that on average at least one resolvable source produces timing residuals in the range ~10-50 ns. Pulsar Timing Arrays, and in particular the future Square Kilometre Array (SKA), can plausibly detect these unique systems, although the events are likely to be rare. These observations would naturally complement on the high-mass end of the massive black hole distribution function future surveys carried out by the Laser Interferometer Space Antenna (LISA)

#### Oct 06, 2008

0809.3412 (/preprints)
2008-10-06, 09:51 

## [0809.3844] Model Waveform Accuracy Standards for Gravitational Wave Data Analysis

Authors: Lee Lindblom, Benjamin J. Owen, Duncan A. Brown

Date: 23 Sep 2008

Abstract: Model waveforms are used in gravitational wave data analysis to detect and then to measure the properties of a source by matching the model waveforms to the signal from a detector. This paper derives accuracy standards for model waveforms which are sufficient to ensure that these data analysis applications are capable of extracting the full scientific content of the data, but without demanding excessive accuracy that would place undue burdens on the model waveform simulation community.

#### Oct 06, 2008

0809.3844 (/preprints)
2008-10-06, 09:50 

## [0809.3730] Experimental Tests of General Relativity: Recent Progress and Future Directions

Authors: Slava G. Turyshev

Date: 22 Sep 2008

Abstract: Einstein's general theory of relativity is the standard theory of gravity, especially where the needs of astronomy, astrophysics, cosmology and fundamental physics are concerned. As such, this theory is used for many practical purposes involving spacecraft navigation, geodesy and time transfer. Here I review the foundations of general relativity, discuss recent progress in the tests of relativistic gravity, and present motivations for the new generation of high-accuracy tests of new physics beyond general relativity. Space-based experiments in fundamental physics are capable today to uniquely address important questions related to the fundamental laws of nature. I discuss the advances in our understanding of fundamental physics that are anticipated in the near future and evaluate the discovery potential of a number of the recently proposed space-based gravitational experiments.

#### Oct 06, 2008

0809.3730 (/preprints)
2008-10-06, 09:50 

## [0809.3533] Turduckening black holes: an analytical and computational study

Authors: David Brown, Peter Diener, Olivier Sarbach, Erik Schnetter, Manuel Tiglio

Date: 20 Sep 2008

Abstract: We provide a detailed analysis of several aspects of the turduckening technique for evolving black holes. At the analytical level we study the constraint propagation for a general family of BSSN-type equations and identify under what conditions the turducken procedure is rigorously justified and under what conditions constraint violations will propagate to the outside of the black holes. We present high-resolution spherically symmetric studies which verify our analytical predictions. Then we present three dimensional simulations of single distorted black holes using different variations of the turduckening method and also the puncture method. We study the effect that these different methods have on the coordinate conditions, constraint violations, and extracted gravitational waves. We find that the waves agree up to small but non-vanishing differences, caused by escaping superluminal gauge modes. These differences become smaller with increasing detector location.

#### Oct 06, 2008

0809.3533 (/preprints)
2008-10-06, 09:49 

## [0809.2814] Gravitational Radiation from Plunging Orbits - Perturbative Study -

Authors: Yasushi Mino, Jeandrew Brink

Date: 16 Sep 2008

Abstract: Numerical relativity has recently yielded a plethora of results about kicks from spinning mergers which has, in turn, vastly increased our knowledge about the spin interactions of black hole systems. In this work we use black hole perturbation theory to calculate accurately the gravitational waves emanating from the end of the plunging stage of an extreme mass ratio merger in order to further understand this phenomenon. This study focuses primarily on spin induced effects with emphasis on the maximally spinning limit and the identification of possible causes of generic behavior.
We find that gravitational waves emitted during the plunging phase exhibit damped oscillatory behavior, corresponding to a coherent excitation of quasi-normal modes by the test particle. This feature is universal in the sense that the frequencies and damping time do not depend on the orbital parameters of the plunging particle. Furthermore, the observed frequencies are distinct from those associated with the usual free quasi-normal ringing. Our calculation suggests that a maximum in radiated energy and momentum occurs at spin parameters equal to $a/M=0.86$ and $a/M=0.81$, respectively for the plunge stage of a polar orbit. The dependence of linear momentum emission on the angle at which a polar orbit impacts the horizon is quantified. One of the advantages of the perturbation approach adopted here is that insight into the actual mechanism of radiation emission and its relationship to black hole ringing is obtained by carefully identifying the dominant terms in the expansions used.

#### Oct 06, 2008

0809.2814 (/preprints)
2008-10-06, 09:48 

## [0809.2809] Bayesian detection of unmodeled bursts of gravitational waves

Authors: Antony C. Searle, Patrick J. Sutton, Massimo Tinto

Date: 16 Sep 2008

Abstract: The data analysis problem of coherently searching for unmodeled gravitational-wave bursts in the data generated by a global network of gravitational-wave observatories has been at the center of research for almost two decades. As data from these detectors is starting to be analyzed, a renewed interest in this problem has been sparked. A Bayesian approach to the problem of coherently searching for gravitational wave bursts with a network of ground-based interferometers is here presented. We demonstrate how to systematically incorporate prior information on the burst signal and its source into the analysis. This information may range from the very minimal, such as best-guess durations, bandwidths, or polarization content, to complete prior knowledge of the signal waveforms and the distribution of sources through spacetime. We show that this comprehensive Bayesian formulation contains several previously proposed detection statistics as special (unphysical) limiting cases, and demonstrate that it outperforms them.

#### Oct 06, 2008

0809.2809 (/preprints)
2008-10-06, 09:47