[0906.5153] Optimal Calibration Accuracy for Gravitational Wave Detectors

Authors: Lee Lindblom

Date: 28 Jun 2009

Abstract: Calibration errors in the response function of a gravitational wave detector degrade its ability to detect and then to measure the properties of any detected signals. This paper derives the needed levels of calibration accuracy for each of these data-analysis tasks. The levels derived here are optimal in the sense that lower accuracy would result in missed detections and/or a loss of measurement precision, while higher accuracy would be made irrelevant by the intrinsic noise level of the detector. Calibration errors affect the data-analysis process in much the same way as errors in theoretical waveform templates. The optimal level of calibration accuracy is expressed therefore as a joint limit on modeling and calibration errors: increased accuracy in one reduces the accuracy requirement in the other.

abs pdf

Jun 30, 2009

0906.5153 (/preprints)
2009-06-30, 18:05 [edit]


[0906.4269] Constraining alternative theories of gravity by gravitational waves from precessing eccentric compact binaries with LISA

Authors: Kent Yagi, Takahiro Tanaka

Date: 23 Jun 2009

Abstract: We calculate how strong one can put constraints on the alternative theories of gravities such as Brans-Dicke and massive graviton theories with LISA. We consider the inspiral gravitational waves from NS/IMBH binaries in Brans-Dicke theory and SMBH/BH binaries in massive graviton theories. We use the 2PN waveforms including spins. We also take both precession and small eccentricity of the orbit into account. We neglect the spin of one of the binary object so that we can apply the so-called \textit{simple precession}. We perform the Monte Carlo simulations of $10ˆ4$ binaries, whose parameters include the Brans-Dicke parameter $\omega_{\mathrm{BD}}$ and the graviton Compton length $\lambda_g$. We find that including both the spin-spin coupling $\sigma$ and the small eccentricity into the binary parameters reduces the determination accuracy by an order of magnitude for the Brans-Dicke case, whilst it has less influence on massive graviton theories. On the other hand, including precession enhances the constraint on $\omega_{\mathrm{BD}}$ only 20% but it increases the constraint on $\lambda_g$ by several factors. For $(1.4+1000)M_{\odot}$ NS/BH binaries of SNR=10, one can put $\omega_{\mathrm{BD}}>7040$, whilst for $(10ˆ7+10ˆ6)M_{\odot}$ BH/BH binaries at 3Gpc, one can put $\lambda_g>4.24\times10ˆ{21}$cm, on average. This is four orders of magnitude stronger than the one obtained from the solar system experiment. From these results, it is understood that the effects of precession and eccentricity cannot be neglected in the parameter estimation analysis.

abs pdf

Jun 29, 2009

0906.4269 (/preprints)
2009-06-29, 08:59 [edit]


[0906.3602] Bounding the mass of the graviton with gravitational waves: Effect of spin precessions in massive black hole binaries

Authors: Adamantios Stavridis (Washington U. St. Louis), Clifford M. Will (Washington U. St. Louis & Institut d'Astrophysique de Paris)

Date: 19 Jun 2009

Abstract: Observations of gravitational waves from massive binary black hole systems at cosmological distances can be used to search for a dependence of the speed of propagation of the waves on wavelength, and thereby to bound the mass of a hypothetical graviton. We study the effects of precessions of the spins of the black holes and of the orbital angular momentum on the process of parameter estimation using matched filtering of gravitational-wave signals vs. theoretical template waveforms. For the proposed space interferometer LISA, we show that precessions, and the accompanying modulations of the gravitational waveforms, are effective in breaking degeneracies among the parameters being estimated, and effectively restore the achievable graviton-mass bounds to levels obtainable from binary inspirals without spin. For spinning, precessing binary black hole systems of equal masses (10ˆ6 solar masses) at 3 Gpc, the bounds on the graviton Compton wavelength achievable are of the order of 5 X 10ˆ{16} km.

abs pdf

Jun 29, 2009

0906.3602 (/preprints)
2009-06-29, 08:59 [edit]


[0906.4246] Long-Term Timing of Millisecond Pulsars and Gravitational Wave Detection

Authors: Joris P.W. Verbiest

Date: 23 Jun 2009

Abstract: (Abridged) This thesis presents long-term timing results on 20 millisecond pulsars (MSPs). It has been predicted that such timing may detect gravitational waves (GWs) - a major (but untested) prediction of general relativity. Our results demonstrate that most of the investigated MSPs have sufficient stability to enable such detection experiments. Furthermore, the timing data of the brightest few sources shows that timing at sub-100 ns precision may be achievable and that, therefore, GW detection within the next decade is likely. Finally, we use our data to place a strong limit on the strength of a predicted background of GWs.

abs pdf

Jun 29, 2009

0906.4246 (/preprints)
2009-06-29, 08:59 [edit]


[0906.4175] Application of Graphics Processing Units to Search Pipeline for Gravitational Waves from Coalescing Binaries of Compact Objects

Authors: Shin Kee Chung, Linqing Wen, David Blair, Kipp Cannon, Amitava Datta

Date: 23 Jun 2009

Abstract: We report a novel application of graphics processing units (GPUs) for the purpose of accelerating the search pipelines for gravitational waves from coalescing binaries of compact objects. A speed-up of 16 fold has been achieved compared with a single central processing unit (CPU). We show that substantial improvements are possible and discuss the reduction in CPU count required for the detection of inspiral sources afforded by the use of GPUs.

abs pdf

Jun 29, 2009

0906.4175 (/preprints)
2009-06-29, 08:59 [edit]


[0906.4923] Gravitational waves production from stellar encounters around massive black holes

Authors: M. De Laurentis, S. Capozziello

Date: 26 Jun 2009

Abstract: The emission of gravitational waves from a system of massive objects interacting on elliptical, hyperbolic and parabolic orbits is studied in the quadrupole approximation. Analytical expressions are then derived for the gravitational wave luminosity, the total energy output and gravitational radiation amplitude. A crude estimate of the expected number of events towards peculiar targets (i.e. globular clusters) is also given. In particular, the rate of events per year is obtained for the dense stellar cluster at the Galactic Center.

abs pdf

Jun 29, 2009

0906.4923 (/preprints)
2009-06-29, 08:58 [edit]


[0906.4968] Computational Approach to Gravitational Waves Forms in Stellar Systems as Complex Structures through Keplerian Parameters

Authors: Ivana Bochicchio, Mariafelicia De Laurentis, Ettore Laserra

Date: 26 Jun 2009

Abstract: In this paper we investigate the gravitational waves emission by stellar dynamical structures as complex systems in the quadrupole approximation considering bounded and unbounded orbits. Precisely, after deriving analytical expressions for the gravitational wave luminosity, the total energy output and gravitational radiation amplitude, we present a computational approach to evaluate the gravitational wave-forms from elliptical, circular, parabolic and hyperbolic orbits as a function of Keplerian parameters.

abs pdf

Jun 29, 2009

0906.4968 (/preprints)
2009-06-29, 08:58 [edit]


[0906.4151] Cosmography with the Einstein Telescope

Authors: B.S. Sathyaprakash (Cardiff University), Bernard Schutz (MPI for Gravitational Physics - Albert Einstein Institute, Cardiff University), Chris Van Den Broeck (Cardiff University)

Date: 23 Jun 2009

Abstract: Einstein Telescope (ET) is a 3rd generation gravitational-wave (GW) detector that is currently undergoing a design study. ET can detect millions of compact binary mergers up to redshifts 2-8. A small fraction of mergers might be observed in coincidence as gamma-ray bursts, helping to measure both the luminosity distance and red-shift to the source. By fitting these measured values to a cosmological model, it should be possible to accurately infer the dark energy equation-of-state, dark matter and dark energy density parameters. ET could, therefore, herald a new era in cosmology.

abs pdf

Jun 29, 2009

0906.4151 (/preprints)
2009-06-29, 08:58 [edit]


[0906.2655] A Xylophone Configuration for a third Generation Gravitational Wave Detector

Authors: Stefan Hild, Simon Chelkowski, Andreas Freise, Janyce Franc, Nazario Morgado, Raffaele Flaminio, Riccardo DeSalvo

Date: 15 Jun 2009

Abstract: Achieving the demanding sensitivity and bandwidth, envisaged for third generation gravitational wave (GW) observatories, is extremely challenging with a single broadband interferometer. Very high optical powers (Megawatts) are required to reduce the quantum noise contribution at high frequencies, while the interferometer mirrors have to be cooled to cryogenic temperatures in order to reduce thermal noise sources at low frequencies. To resolve this potential conflict of cryogenic test masses with high thermal load, we present a conceptual design for a 2-band xylophone configuration for a third generation GW observatory, composed of a high-power, high-frequency interferometer and a cryogenic low-power, low-frequency instrument. Featuring inspiral ranges of 3200Mpc and 38000Mpc for binary neutron stars and binary black holes coalesences, respectively, we find that the potential sensitivity of xylophone configurations can be significantly wider and better than what is possible in a single broadband interferometer.

abs pdf

Jun 20, 2009

0906.2655 (/preprints)
2009-06-20, 11:10 [edit]


[0906.3174] The Equivalence Principle and the Constants of Nature

Authors: Thibault Damour

Date: 17 Jun 2009

Abstract: We briefly review the various contexts within which one might address the issue of ‘why’ the dimensionless constants of Nature have the particular values that they are observed to have. Both the general historical trend, in physics, of replacing a-priori-given, absolute structures by dynamical entities, and anthropic considerations, suggest that coupling ‘constants’ have a dynamical nature. This hints at the existence of observable violations of the Equivalence Principle at some level, and motivates the need for improved tests of the Equivalence Principle.

abs pdf

Jun 20, 2009

0906.3174 (/preprints)
2009-06-20, 11:10 [edit]


[0906.3003] On the gravitational polarizability of black holes

Authors: Thibault Damour, Orchidea Maria Lecian

Date: 16 Jun 2009

Abstract: The gravitational polarizability properties of black holes are compared and contrasted with their electromagnetic polarizability properties. The ‘shape’ or ‘height’ multipolar Love numbers h_l of a black hole are defined and computed. They are then compared to their electromagnetic analogs h_lˆ{EM}. The Love numbers h_l give the height of the l-th multipolar ‘tidal bulge’ raised on the horizon of a black hole by faraway masses. We also discuss the shape of the tidal bulge raised by a test mass m, in the limit where m gets very close to the horizon.

abs pdf

Jun 20, 2009

0906.3003 (/preprints)
2009-06-20, 11:10 [edit]


[0906.2433] Un-modeled search for black hole binary systems in the NINJA project

Authors: Laura Cadonati, Shourov Chatterji, Sebastian Fischetti, Gianluca Guidi, Satyanarayan R. P. Mohapatra, Riccardo Sturani, Andrea Viceré

Date: 12 Jun 2009

Abstract: The gravitational wave signature from binary black hole coalescences is an important target for LIGO and VIRGO. The Numerical INJection Analysis (NINJA) project brought together the numerical relativity and gravitational wave data analysis communities, with the goal to optimize the detectability of these events. In its first instantiation, the NINJA project produced a simulated data set with numerical waveforms from binary black hole coalescences of various morphologies (spin, mass ratio, initial conditions), superimposed to Gaussian colored noise at the design sensitivity for initial LIGO and VIRGO. We analyzed this simulated data set with the Q-pipeline burst algorithm. This code, designed for the all-sky detection of gravitational wave bursts with minimal assumptions on the shape of the waveform, filters the data with a bank of sine-Gaussians, or sinusoids with Gaussian envelope. The algorithm's performance was compared to matched filtering with ring-down templates. The results are qualitatively consistent; however due to the low simulation statistics in the first NINJA project, it is premature to draw quantitative conclusions at this stage.

abs pdf

Jun 20, 2009

0906.2433 (/preprints)
2009-06-20, 11:10 [edit]


[0906.2520] Testing Relativistic Gravity from Space

Authors: Slava G. Turyshev

Date: 14 Jun 2009

Abstract: Recent experiments have successfully tested Einstein's general theory of relativity to remarkable precision. We discuss recent progress in the tests of relativistic gravity in the solar system and present motivations for the new generation of high-accuracy gravitational experiments. We especially focus on the concepts aiming to probe parameterized-post-Newtonian parameter $\gamma$ and evaluate the discovery potential of the recently proposed experiments.

abs pdf

Jun 20, 2009

0906.2520 (/preprints)
2009-06-20, 11:10 [edit]


[physics/9710036] Radiation from a charged particle and radiation reaction -- revisited

Authors: Abhinav Gupta, T. Padmanabhan

Date: 27 Oct 1997

Abstract: We study the electromagnetic fields of an arbitrarily moving charged particle and the radiation reaction on the charged particle using a novel approach. We first show that the fields of an arbitrarily moving charged particle in an inertial frame can be related in a simple manner to the fields of a uniformly accelerated charged particle in its rest frame. Since the latter field is static and easily obtainable, it is possible to derive the fields of an arbitrarily moving charged particle by a coordinate transformation. More importantly, this formalism allows us to calculate the self-force on a charged particle in a remarkably simple manner. We show that the original expression for this force, obtained by Dirac, can be rederived with much less computation and in an intuitively simple manner using our formalism.

abs pdf

Jun 20, 2009

9710036 (/preprints/physics)
2009-06-20, 11:08 [edit]


[0906.2367] Uniqueness of Extremal Kerr and Kerr-Newman Black Holes

Authors: Aaron J. Amsel, Gary T. Horowitz, Donald Marolf, Matthew M. Roberts

Date: 12 Jun 2009

Abstract: We prove that the only four dimensional, stationary, rotating, asymptotically flat vacuum black hole with a single degenerate horizon is given by the extremal Kerr solution. We also prove a similar uniqueness theorem for the extremal Kerr-Newman solution. This closes a longstanding gap in the black hole uniqueness theorems.

abs pdf

Jun 15, 2009

0906.2367 (/preprints)
2009-06-15, 10:25 [edit]


[0906.2226] On post-Newtonian orbits and the Galactic-center stars

Authors: Miguel Preto, Prasenjit Saha

Date: 12 Jun 2009

Abstract: Stars near the Galactic center reach a few percent of light speed during pericenter passage, which makes post-Newtonian effects potentially detectable. We formulate the orbit equations in Hamiltonian form such that the $O(vˆ2/cˆ2)$ and $O(vˆ3/cˆ3)$ post-Newtonian effects of the Kerr metric appear as a simple generalization of the Kepler problem. A related perturbative Hamiltonian applies to photon paths. We then derive a symplectic integrator with adaptive time-steps, for fast and accurate numerical calculation of post-Newtonian effects. Using this integrator, we explore relativistic effects. Taking the star S2 as an example, we find that general relativity would contribute tenths of mas in astrometry and tens of $\rm km sˆ{-1}$ in kinematics. (For eventual comparison with observations, redshift and time-delay contributions from the gravitational field on light paths will need to be calculated, but we do attempt these in the present paper.) The contribution from stars, gas, and dark matter in the Galactic center region is still poorly constrained observationally, but current models suggest that the resulting Newtonian perturbation on the orbits could plausibly be of the same order as the relativistic effects for stars with semi-major axes $\gtrsim 0.01$ pc (or 250 mas). Nevertheless, the known and distinctive {\it time dependence} of the relativistic perturbations may make it possible to disentangle and extract both effects from observations.

abs pdf

Jun 15, 2009

0906.2226 (/preprints)
2009-06-15, 10:24 [edit]


[0906.2119] Black Holes at Work

Authors: A.C.Fabian

Date: 11 Jun 2009

Abstract: Massive black holes are ubiquitous, occurring at the centres of all massive galaxies and possibly many low mass ones. They are no ornament which just happens to be there, but play a role vital to the growth and structure of the host galaxy. How they do this has come to be known as cosmic feedback and how it works, indeed how black holes work, is the subject of this paper.

abs pdf

Jun 12, 2009

0906.2119 (/preprints)
2009-06-12, 11:03 [edit]


[0906.1563] Investigating Dark Energy with Black Hole Binaries

Authors: Laura Mersini-Houghton, Adam Kelleher

Date: 8 Jun 2009

Abstract: The accelerated expansion of the universe is ascribed to the existence of dark energy. Black holes accretion of dark energy induces a mass change proportional to the energy density and pressure of the background dark energy fluid. The time scale during which the mass of black holes changes considerably is too long relative to the age of the universe, thus beyond detection possibilities. We propose to take advantage of the modified black hole masses for exploring the equation of state $w[z]$ of dark energy, by investigating the evolution of supermassive black hole binaries on a dark energy background. Deriving the signatures of dark energy accretion on the evolution of binaries, we find that dark energy imprints on the emitted gravitational radiation and on the changes in the orbital radius of the binary can be within detection limits for certain supermassive black hole binaries. In this talk I describe how binaries can provide a useful tool in obtaining complementary information on the nature of dark energy, based on the work done with A.Kelleher.

abs pdf

Jun 11, 2009

0906.1563 (/preprints)
2009-06-11, 16:00 [edit]


[0906.1448] Gravitational waveforms for 2- and 3-body gravitating systems

Authors: Yuji Torigoe, Keisuke Hattori, Hideki Asada

Date: 8 Jun 2009

Abstract: Different numbers of self-gravitating particles (in different types of periodic motion) are most likely to generate very different shapes of gravitational waves, some of which, however, can be accidentally almost the same. One such example is a binary and a three-body system for Lagrange's solution. To track the evolution of these similar waveforms, we define a chirp mass to the triple system. Thereby, we show that the quadrupole waveforms cannot distinguish the sources. It is suggested that waveforms with higher $\ell$-th multipoles will be important for classification of them (with a conjecture of $\ell \leq N$ for N particles).

abs pdf

Jun 11, 2009

0906.1448 (/preprints)
2009-06-11, 15:59 [edit]


[0906.1366] Relativistic theory of tidal Love numbers

Authors: Taylor Binnington, Eric Poisson

Date: 7 Jun 2009

Abstract: In Newtonian gravitational theory, a tidal Love number relates the mass multipole moment created by tidal forces on a spherical body to the applied tidal field. The Love number is dimensionless, and it encodes information about the body's internal structure. We present a relativistic theory of Love numbers, which applies to compact bodies with strong internal gravities; the theory extends and completes a recent work by Flanagan and Hinderer, which revealed that the tidal Love number of a neutron star can be measured by Earth-based gravitational-wave detectors. We consider a spherical body deformed by an external tidal field, and provide precise and meaningful definitions for electric-type and magnetic-type Love numbers; and these are computed for polytropic equations of state. The theory applies to black holes as well, and we find that the relativistic Love numbers of a nonrotating black hole are all zero.

abs pdf

Jun 11, 2009

0906.1366 (/preprints)
2009-06-11, 15:58 [edit]


[0906.1769] The Effective One Body description of the Two-Body problem

Authors: Thibault Damour, Alessandro Nagar

Date: 9 Jun 2009

Abstract: The Effective One Body (EOB) formalism is an analytical approach which aims at providing an accurate description of the motion and radiation of coalescing binary black holes with arbitrary mass ratio. We review the basic elements of this formalism and discuss its aptitude at providing accurate template waveforms to be used for gravitational wave data analysis purposes.

abs pdf

Jun 11, 2009

0906.1769 (/preprints)
2009-06-11, 15:58 [edit]


[0906.0399] The Pioneer Anomaly in the Light of New Data

Authors: Slava G. Turyshev, Viktor T. Toth

Date: 2 Jun 2009

Abstract: The radio-metric tracking data received from the Pioneer 10 and 11 spacecraft from the distances between 20-70 astronomical units from the Sun has consistently indicated the presence of a small, anomalous, blue-shifted Doppler frequency drift that limited the accuracy of the orbit reconstruction for these vehicles. This drift was interpreted as a sunward acceleration of a_P = (8.74+/-1.33)x10ˆ{-10} m/sˆ2 for each particular spacecraft. This signal has become known as the Pioneer anomaly; the nature of this anomaly is still being investigated.
Recently new Pioneer 10 and 11 radio-metric Doppler and flight telemetry data became available. The newly available Doppler data set is much larger when compared to the data used in previous investigations and is the primary source for new investigation of the anomaly. In addition, the flight telemetry files, original project documentation, and newly developed software tools are now used to reconstruct the engineering history of spacecraft. With the help of this information, a thermal model of the Pioneers was developed to study possible contribution of thermal recoil force acting on the spacecraft. The goal of the ongoing efforts is to evaluate the effect of on-board systems on the spacecrafts' trajectories and possibly identify the nature of this anomaly.
Techniques developed for the investigation of the Pioneer anomaly are applicable to the New Horizons mission. Analysis shows that anisotropic thermal radiation from on-board sources will accelerate this spacecraft by ~41 x 10ˆ{-10} m/sˆ2. We discuss the lessons learned from the study of the Pioneer anomaly for the New Horizons spacecraft.

abs pdf

Jun 07, 2009

0906.0399 (/preprints)
2009-06-07, 09:59 [edit]


[0906.0660] Relativistic Positioning Systems: current status

Authors: Bartolomé Coll, Joan J. Ferrando, Juan A. Morales-Lladosa

Date: 3 Jun 2009

Abstract: A {\em relativistic positioning system} consists in a set of four clocks broadcasting their respective proper time by means of light signals. Among them, the more important ones are the {\em auto-located positioning systems,} in which every clock broadcasts not only its proper time but also the proper times that it receives from the other three. At this level, no reference to any exterior system (the Earth surface, for example) and no synchronization are needed. The current status of the theory of relativistic positioning systems is sketched.

abs pdf

Jun 07, 2009

0906.0660 (/preprints)
2009-06-07, 09:59 [edit]


[0906.0461] Gravitational wave backgrounds and the cosmic transition from Population III to Population II stars

Authors: Stefania Marassi, Raffaella Schneider, Valeria Ferrari

Date: 2 Jun 2009

Abstract: Using the results of a numerical simulation which follows the evolution, metal enrichment and energy deposition of both Population III and Population II stars, we predict the redshift dependence of the formation rate of black hole remnants of Population III stars with masses 100- 500Msun and of neutron stars(black holes) remnants of Population II stars with masses 8-20Msun (20-40Msun). We describe the gravitational wave spectrum produced by Population III and Population II sources adopting the most appropriate signals available in the literature and we compute the stochastic backgrounds resulting from the cumulative emission of these sources throughout the history of the Universe. With the aim of assessing whether these backgrounds might act as foregrounds for signals generated in the Inflationary epoch, we compare their amplitudes with the sensitivity of currently planned and future ground/space-based interferometers.

abs pdf

Jun 07, 2009

0906.0461 (/preprints)
2009-06-07, 09:59 [edit]


[0906.0968] New analytical methods for gravitational radiation and reaction in binaries with arbitrary mass ratio and relative velocity

Authors: Chad R. Galley, Bei-Lok Hu

Date: 4 Jun 2009

Abstract: We present a new analytical framework for describing the dynamics of a gravitational binary system with unequal masses moving with arbitrary relative velocity, taking into account the backreaction from both compact objects in the form of tidal deformation, gravitational waves and self forces. Allowing all dynamical variables to interact with each other in a self-consistent manner this formalism ensures that all the dynamical quantities involved are conserved on the background spacetime and obey the gauge invariance under general coordinate transformations that preserve the background geometry. Because it is based on a generalized perturbation theory and the important new emphasis is on the self-consistency of all the dynamical variables involved we call it a gravitational perturbation theory with self-consistent backreaction (GP-SCB).
As an illustration of how this formalism is implemented we construct perturbatively a self-consistent set of equations of motion for an inspiraling gravitational binary, which does not require extra assumptions such as slow motion, weak-field or small mass ratio for its formulation. This case should encompass the inspiral and possibly the plunge and merger phases of binaries with otherwise general parameters (e.g., mass ratio and relative velocity) though more investigation is needed to substantiate it.
In the second part, we discuss how the mass ratio can be treated as a perturbation parameter in the post-Newtonian effective field theory (PN-EFT) approach, thus extending the work of Goldberger and Rothstein for equal mass binaries to variable mass ratios. We provide rough estimates for the higher post-Newtonian orders needed to determine the number of gravitational wave cycles, with a specified precision, that fall into a detector's bandwidth.

abs pdf

Jun 07, 2009

0906.0968 (/preprints)
2009-06-07, 09:59 [edit]


[0906.0023] Exploiting global correlations to detect continuous gravitational waves

Authors: Holger J. Pletsch, Bruce Allen

Date: 31 May 2009

Abstract: Fully coherent searches (over realistic ranges of parameter space and year-long observation times) for unknown sources of continuous gravitational waves are computationally prohibitive. Less expensive hierarchical searches divide the data into shorter segments which are analyzed coherently, then detection statistics from different segments are combined incoherently. Here, we present an improved method for the incoherent step, the Global Correlation Transform (GCT), which exploits global parameter-space correlations in the coherent detection statistic. Application to simulated data shows significant sensitivity improvements compared with previously available methods, increasing the spatial volume probed by more than two orders of magnitude at lower computational cost.

abs pdf

Jun 07, 2009

0906.0023 (/preprints)
2009-06-07, 09:59 [edit]


[0906.0093] How to observe a non-Kerr spacetime

Authors: Theocharis A. Apostolatos, Georgios Lukes-Gerakopoulos, George Contopoulos

Date: 30 May 2009

Abstract: We present a generic criterion which can be used in gravitational-wave data analysis to distinguish an extreme-mass-ratio inspiral into a Kerr background spacetime from one into a non-Kerr background spacetime. The criterion exploits the fact that when an integrable system, such as the system that describes geodesic orbits in a Kerr spacetime, is perturbed, the tori in phase space which initially corresponded to resonances disintegrate so as to form the so called Birkhoff chains on a surface of section, according to the Poincar\'{e}-Birkhoff theorem. The KAM curves of these islands in such a chain share the same ratio of frequencies, even though the frequencies themselves vary from one KAM curve to another inside an island. On the other hand, the KAM curves, which do not lie in a Birkhoff chain, do not share this characteristic property. Such a temporal constancy of the ratio of frequencies during the evolution of the gravitational-wave signal will signal a non-Kerr spacetime which could then be further explored.

abs pdf

Jun 07, 2009

0906.0093 (/preprints)
2009-06-07, 09:59 [edit]


[0906.0096] Relativistic tidal properties of neutron stars

Authors: Thbiault Damour, Alessandro Nagar

Date: 30 May 2009

Abstract: We study the various linear responses of neutron stars to external relativistic tidal fields. We focus on three different tidal responses, associated to three different tidal coefficients: (i) a gravito-electric-type coefficient G\mu_\ell=[length]ˆ{2\ell+1} measuring the \ellˆ{th}-order mass multipolar moment GM_{a_1… a_\ell} induced in a star by an external \ellˆ{th}-order gravito-electric tidal field G_{a_1… a_\ell}; (ii) a gravito-magnetic-type coefficient G\sigma_\ell=[length]ˆ{2\ell+1} measuring the \ellˆ{th} spin multipole moment G S_{a_1… a_\ell} induced in a star by an external \ellˆ{th}-order gravito-magnetic tidal field H_{a_1… a_\ell}; and (iii) a dimensionless ‘shape’ Love number h_\ell measuring the distorsion of the shape of the surface of a star by an external \ellˆ{th}-order gravito-electric tidal field. All the dimensionless tidal coefficients G\mu_\ell/Rˆ{2\ell+1}, G\sigma_\l/Rˆ{2\ell+1} and h_\ell (where R is the radius of the star) are found to have a strong sensitivity to the value of the star's ‘compactness’ c\equiv GM/(c_0ˆ2 R) (where we indicate by c_0 the speed of light). In particular, G\mu_\l/Rˆ{2\l+1}\sim k_\ell is found to strongly decrease, as c increases, down to a zero value as c is formally extended to the ‘black-hole limit’ cˆ{BH}=½. The shape Love number h_\ell is also found to significantly decrease as c increases, though it does not vanish in the formal limit c\to cˆ{BH}. The formal vanishing of \mu_\ell and \sigma_\ell as c\to cˆ{BH} is a consequence of the no-hair properties of black holes; this suggests, but in no way proves, that the effective action describing the gravitational interactions of black holes may not need to be augmented by nonminimal worldline couplings.

abs pdf

Jun 07, 2009

0906.0096 (/preprints)
2009-06-07, 09:59 [edit]


[0906.0313] Post-Circular Expansion of Eccentric Binary Inspirals: Fourier-Domain Waveforms in the Stationary Phase Approximation

Authors: Nicolas Yunes, K. G. Arun, Emanuele Berti, Clifford M. Will

Date: 1 Jun 2009

Abstract: We lay the foundations for the construction of analytic expressions for Fourier-domain gravitational waveforms produced by eccentric, inspiraling compact binaries in a post-circular or small-eccentricity approximation. The time-dependent, "plus" and "cross" polarizations are expanded in Bessel functions, which are then self-consistently re-expanded in a power series about zero initial eccentricity to eighth order. The stationary phase approximation is then employed to obtain explicit analytic expressions for the Fourier transform of the post-circular expanded, time-domain signal. We exemplify this framework by considering Newtonian-accurate waveforms, which in the post-circular scheme give rise to higher harmonics of the orbital phase and amplitude corrections both to the amplitude and the phase of the Fourier domain waveform. Such higher harmonics lead to an effective increase in the inspiral mass reach of a detector as a function of the binary's eccentricity e_0 at the time when the binary enters the detector sensitivity band. Using the largest initial eccentricity allowed by our approximations (e_0 < 0.4), the mass reach is found to be enhanced up to factors of approximately 5 relative to that of circular binaries for Advanced LIGO, LISA, and the proposed Einstein Telescope at a signal-to-noise ratio of ten. A post-Newtonian generalization of the post circular scheme is also discussed, which holds the promise to provide "ready-to-use" Fourier-domain waveforms for data analysis of eccentric inspirals.

abs pdf

Jun 07, 2009

0906.0313 (/preprints)
2009-06-07, 09:58 [edit]


[0906.0889] Quasiequilibrium states of black hole-neutron star binaries in the moving-puncture framework

Authors: Koutarou Kyutoku, Masaru Shibata, Keisuke Taniguchi

Date: 4 Jun 2009

Abstract: General relativistic quasiequilibrium states of black hole-neutron star binaries are computed in the moving-puncture framework. We propose three conditions for determining the quasiequilibrium states and compare the numerical results with those obtained in the excision framework. We find that the results obtained in the moving-puncture framework agree with those in the excision framework and with those in the third post-Newtonian approximation for the cases that (i) the mass ratio of the binary is close to unity irrespective of the orbital separation, and (ii) the orbital separation is large enough ($m_0\Omega \alt 0.02$ where $m_0$ and $\Omega$ are the total mass and the orbital angular velocity, respectively) irrespective of the mass ratio. For $m_0 \Omega \agt 0.03$, both of the results in the moving-puncture and excision frameworks deviate, more or less, from those in the third post-Newtonian approximation. Thus the numerical results do not provide a quasicircular state, rather they seem to have a nonnegligible eccentricity of order 0.01--0.1. We show by numerical simulation that a method in the moving-puncture framework can provide approximately quasicircular states in which the eccentricity is by a factor of $\sim 2$ smaller than those in quasiequilibrium given by other approaches.

abs pdf

Jun 07, 2009

0906.0889 (/preprints)
2009-06-07, 09:58 [edit]


[0905.4832] Sparse sky grid for the coherent detection of gravitational wave bursts

Authors: Olivier Rabaste, Eric Chassande-Mottin, Archana Pai

Date: 29 May 2009

Abstract: The gravitational wave detectors currently in operation perform the analysis of their scientific data jointly. Concerning the search for bursting sources, coherent data analysis methods have been shown to be more efficient. In the coherent approach, the data collected by the detectors are time-shifted and linearly combined so that the signatures received by each detector add up constructively (thus improving the resulting signal-to-noise ratio). This operation has to be performed over a sky grid (which determines the sky locations to be searched). A limitation of those pipelines is their large computing cost. One of the available degrees of freedom to reduce the cost is the choice of the sky grid. Ideally, the sky sampling scheme should adapt the angular resolution associated with the considered gravitational wave detector network. As the geometry of detector network is not regular (the detectors are not equally spaced and oriented), the angular resolution varies largely depending on the sky location. We propose here a procedure which designs sky grids that permit a complete sky coverage with a minimum number of vertices and thus adapt the local resolution.

abs pdf

Jun 01, 2009

0905.4832 (/preprints)
2009-06-01, 20:07 [edit]


[0905.4803] Holographic Noise in Interferometers

Authors: Craig J. Hogan

Date: 29 May 2009

Abstract: General arguments based on black hole physics suggest the possibility of a new kind of indeterminacy in the relative position of bodies in spacetime, corresponding to the diffraction limit of Planck wavelength radiation. Suitably designed instruments should display a new phenomenon, a randomly varying shear in relative position, with a flat power spectral density at low frequencies given approximately by the Planck time, and with no other parameters. An effective theory is presented to connect fundamental theory with macroscopic phenomena, such as the statistical properties of noise in signals of interferometers. A theory of spacetime wavefunctions based on the paraxial wave equation with a carrier wave at the Planck frequency, or equivalently a Schrodinger wave equation, is motivated by a particular interpretation of Matrix theory in the macroscopic limit. A model based on gaussian-beam solutions of this equation is used to derive formulas in the time and frequency domain for autocorrelation of beamsplitter position. The cross-correlation between two non-coincident interferometers as a function of separation is estimated. The cross-correlation signature may be exploited in the design of experiments to provide convincing evidence for or against the holographic hypothesis.

abs pdf

Jun 01, 2009

0905.4803 (/preprints)
2009-06-01, 20:06 [edit]


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