[0711.4644] Verifying black hole orbits with gravitational spectroscopy

Authors: Steve Drasco

Date: 29 Nov 2007

Abstract: Gravitational waves from test masses bound to geodesic orbits of rotating black holes are simulated, using Teukolsky's black hole perturbation formalism, for about ten thousand generic orbital configurations. Each binary radiates power exclusively in modes with frequencies that are integer-linear-combinations of the orbit's three fundamental frequencies. The following general spectral properties are found with a survey of orbits: (i) 99% of the radiated power is typically carried by a few hundred modes, and at most by about a thousand modes, (ii) the dominant frequencies can be grouped into a small number of families defined by fixing two of the three integer frequency multipliers, and (iii) the specifics of these trends can be qualitatively inferred from the geometry of the orbit under consideration. Detections using tri-periodic analytic templates modeled on these general properties would constitute a verification of radiation from an adiabatic sequence of black hole orbits, and would recover the evolution of the fundamental orbital frequencies. In an analogy with ordinary spectroscopy, this would compare to observing the Bohr model's atomic hydrogen spectrum without being able to rule out alternative atomic theories or nuclei. The suitability of such a detection technique is demonstrated using snapshots computed at twelve-hour intervals throughout the last three years before merger of a kludged inspiral. Due to circularization, the number of excited modes decreases as the binary evolves. A hypothetical detection algorithm that tracks mode families dominating the first twelve hours of the inspiral would capture 98% of the total power over the remaining three years.

abs pdf

Nov 30, 2007

0711.4644 (/preprints)
2007-11-30, 09:52 [edit]


[0711.4620] Critical phenomena in gravitational collapse

Authors: Carsten Gundlach, Jose M. Martin-Garcia

Date: 28 Nov 2007

Abstract: As first discovered by Choptuik, the black hole threshold in the space of initial data for general relativity shows both surprising structure and surprising simplicity. Universality, power-law scaling of the black hole mass, and scale echoing have given rise to the term "critical phenomena". They are explained by the existence of exact solutions which are attractors within the black hole threshold, that is, attractors of codimension one in phase space, and which are typically self-similar. Critical phenomena give a natural route from smooth initial data to arbitrarily large curvatures visible from infinity, and are therefore likely to be relevant for cosmic censorship, quantum gravity, astrophysics, and our general understanding of the dynamics of general relativity.

abs pdf

Nov 30, 2007

0711.4620 (/preprints)
2007-11-30, 09:51 [edit]


[astro-ph/0602470] LISA observations of massive black hole mergers: event rates and issues in waveform modelling

Authors: Emanuele Berti

Date: 21 Feb 2006

Abstract: The observability of gravitational waves from supermassive and intermediate-mass black holes by the forecoming Laser Interferometer Space Antenna (LISA), and the physics we can learn from the observations, will depend on two basic factors: the event rates for massive black hole mergers occurring in the LISA best sensitivity window, and our theoretical knowledge of the gravitational waveforms. We first provide a concise review of the literature on LISA event rates for massive black hole mergers, as predicted by different formation scenarios. Then we discuss what (in our view) are the most urgent issues to address in terms of waveform modelling. For massive black hole binary inspiral these include spin precession, eccentricity, the effect of high-order Post-Newtonian terms in the amplitude and phase, and an accurate prediction of the transition from inspiral to plunge. For black hole ringdown, numerical relativity will ultimately be required to determine the relative quasinormal mode excitation, and to reduce the dimensionality of the template space in matched filtering.

abs pdf

Nov 29, 2007

0602470 (/preprints/astro-ph)
2007-11-29, 14:41 [edit]


[0710.0258] Next to leading order gravitational wave emission and dynamical evolution of compact binary systems with spin

Authors: Dörte Hansen

Date: 1 Oct 2007

Abstract: Compact binary systems with spinning components are considered. Finite size effects due to rotational deformation are taken into account. The dynamical evolution and next to leading order gravitational wave forms are calculated, taking into account the orbital motion up to the first post-Newtonian approximation.

abs pdf

Nov 29, 2007

0710.0258 (/preprints)
2007-11-29, 10:10 [edit]


[0711.4558] The influence of the hydrodynamic drag from an accretion torus on extreme mass-ratio inspirals

Authors: E. Barausse (SISSA, Italy), L. Rezzolla (AEI, Germany)

Date: 28 Nov 2007

Abstract: We have studied extreme mass-ratio inspirals (EMRIs) in spacetimes containing a rotating black hole and a non self-gravitating torus with constant specific angular momentum. We have found that the effect of the hydrodynamic drag exerted by the torus on the satellite is much smaller than the corresponding one due to radiation reaction, for systems such as those generically expected in AGNs and at distances from the SMBH which can be probed with LISA. However, given the uncertainty on the parameters of these systems, there exist configurations in which the effect of the hydrodynamic drag can be comparable to the radiation-reaction one in phases of the inspiral which are detectable by LISA. This is the case, for instance, for a 10ˆ6 M_sun SMBH surrounded by a corotating torus of comparable mass and with radius of 10ˆ3-10ˆ4 gravitational radii, or for a 10ˆ5 M_sun SMBH surrounded by a corotating 10ˆ4 M_sun torus with radius of 10ˆ5 gravitational radii. Should these conditions be met in astrophysical systems, EMRI-gravitational waves could provide a characteristic signature of the presence of the torus. In fact, while radiation reaction always increases the inclination of the orbit with respect to the equatorial plane, the hydrodynamic drag from a torus corotating with the SMBH always decreases it. However, even when initially dominating over radiation reaction, the influence of the hydrodynamic drag decays very rapidly as the satellite moves into the very strong-field region of the SMBH (i.e., p <~ 5M). Although our results have been obtained for a specific class of tori, we argue that they will be qualitatively valid also for more generic distributions of the specific angular momentum.

abs pdf

Nov 29, 2007

0711.4558 (/preprints)
2007-11-29, 10:10 [edit]


[0711.4039] An Evidence Based Time-Frequency Search Method for Gravitational Waves from Pulsar Glitches

Authors: J Clark, I S Heng, M Pitkin, G Woan

Date: 26 Nov 2007

Abstract: We review and expand on a Bayesian model selection technique for the detection of gravitational waves from neutron star ring-downs associated with pulsar glitches. The algorithm works with power spectral densities constructed from overlapping time segments of gravitational wave data. Consequently, the original approach was at risk of falsely identifying multiple signals where only one signal was present in the data. We introduce an extension to the algorithm which uses posterior information on the frequency content of detected signals to cluster events together. The requirement that we have just one detection per signal is now met with the additional bonus that the belief in the presence of a signal is boosted by incorporating information from adjacent time segments.

abs pdf

Nov 27, 2007

0711.4039 (/preprints)
2007-11-27, 08:39 [edit]


[0711.3048] Volumes of Space as Subsystems

Authors: Federico Piazza, Fabio Costa

Date: 20 Nov 2007

Abstract: As a novel approach with possible relevance to semiclassical gravity, we propose to define regions of space as quantum subsystems. After recalling how to divide a generic quantum system into ‘parts’, we apply this idea to a free scalar field in Minkowski space and we compare two different localization schemes. The first scheme is the standard one, induced by the local relativistic fields; the alternative scheme that we consider is the one induced by the Newton-Wigner operators. If degrees of freedom are divided according to the latter, the Hamiltonian of the field exhibits a certain amount of non-locality. Moreover, when a region of space is cut off from the rest according to the Newton-Wigner scheme, the geometric entropy is finite and exhibits a sensible thermodynamic behaviour.

abs pdf

Nov 21, 2007

0711.3048 (/preprints)
2007-11-21, 13:06 [edit]


[0711.3007] Modulation of the gravitational waveform by the effect of radiation reaction

Authors: Yasushi Mino

Date: 19 Nov 2007

Abstract: When we calculate the gravitational waveform from the extreme-mass-ratio inspirals (EMRIs) by metric perturbation, it is a common strategy to use the adiabatic approximation. By the adiabatic approximation, we first calculate the waveform by the linear metric perturbation induced by geodesics orbiting a black hole, then we calculate the adiabatic evolution of the parameters of geodesics due to the radiation reaction effect through the calculation of the self-force. This procedure is considered to be reasonable, however, there is no direct proof that it can actually produce the correct waveform we would observe. In this paper, we study the formal expression of the second order metric perturbation and show that the waveform by the second order metric perturbation does have the feature that the linear metric perturbation is actually modulated by the adiabatic evolution of the geodesic. This evidence supports that the adiabatic approximation can actually produce the correct waveform and that the adiabatic expansion we propose is a more appropriate perturbation expansion to study the radiation reaction effect on the gravitational waveform.

abs pdf

Nov 21, 2007

0711.3007 (/preprints)
2007-11-21, 13:05 [edit]


[0711.2420] Tidal Love numbers of neutron stars

Authors: Tanja Hinderer

Date: 15 Nov 2007

Abstract: For a variety of fully relativistic polytropic neutron star models we calculate the star's tidal Love number k2. Most realistic equations of state for neutron stars can be approximated as a polytrope with an effective index ñ0.5-1.0. The equilibrium stellar model is obtained by numerical integration of the Tolman-Oppenheimer-Volkhov equations. We calculate the linear l=2 static perturbations to the Schwarzschild spacetime following the method of Thorne and Campolattaro. Combining the perturbed Einstein equations into a single second order differential equation for the perturbation to the metric coefficient g_tt, and matching the exterior solution to the asymptotic expansion of the metric in the star's local asymptotic rest frame gives the Love number. Our results agree well with the Newtonian results in the weak field limit. The fully relativistic values differ from the Newtonian values by up to ~24%. The Love number is potentially measurable in gravitational wave signals from inspiralling binary neutron stars.

abs pdf

Nov 19, 2007

0711.2420 (/preprints)
2007-11-19, 10:13 [edit]


[0711.2628] Comparing Effective-One-Body gravitational waveforms to accurate numerical data

Authors: Thibault Damour, Alessandro Nagar

Date: 16 Nov 2007

Abstract: We continue the program of constructing, within the Effective-One-Body (EOB) approach, high accuracy, faithful analytic waveforms describing the gravitational wave signal emitted by inspiralling and coalescing binary black holes (BHs). We present the comparable-mass version of a new, resummed 3PN-accurate EOB quadrupolar waveform recently introduced in the small-mass-ratio limit. We compare the phase and the amplitude of this waveform to the recently published results of a high-accuracy numerical relativity (NR) simulation of 15 orbits of an inspiralling equal-mass binary BHs system performed by the Caltech-Cornell group. We find a remarkable agreement, both in phase and in amplitude, between the new EOB waveform and the published numerical data. More precisely: (i) in the gravitational wave (GW) frequency domain $M\omega <0.08$ where the phase of one of the non-resummed ‘Taylor approximant’ (T4) waveform matches well with the numerical relativity one, we find that the EOB phase fares as well, while (ii) for higher GW frequencies, $0.08<M\omega\lesssim 0.14$, where the TaylorT4 approximant starts to significantly diverge from the NR phase, we show that the EOB phase continues to match well the NR one. We further propose various methods of tuning the two inspiral flexibility parameters, $a_5$ and $v_{\rm pole}$, of the EOB waveform so as to ‘best fit’ EOB predictions to numerical data. We find that the maximal dephasing between EOB and NR can then be reduced below $10ˆ{-3}$ GW cycles over the entire span (30 GW cycles) of the simulation. Our resummed EOB amplitude agrees much better with the NR one than any of the previously considered non-resummed, post-Newtonian one.

abs pdf

Nov 19, 2007

0711.2628 (/preprints)
2007-11-19, 10:08 [edit]


[0711.2170] Summary of GR18 Numerical Relativity parallel sessions (B1/B2 and B2), Sydney, 8-13 July 2007

Authors: Carsten Gundlach

Date: 14 Nov 2007

Abstract: The numerical relativity session at GR18 was dominated by physics results on binary black hole mergers. Several groups can now simulate these from a time when the post-Newtonian equations of motion are still applicable, through several orbits and the merger to the ringdown phase, obtaining plausible gravitational waves at infinity, and showing some evidence of convergence with resolution. The results of different groups roughly agree. This new-won confidence has been used by these groups to begin mapping out the (finite-dimensional) initial data space of the problem, with a particular focus on the effect of black hole spins, and the acceleration by gravitational wave recoil to hundreds of km/s of the final merged black hole. Other work was presented on a variety of topics, such as evolutions with matter, extreme mass ratio inspirals, and technical issues such as gauge choices.

abs pdf

Nov 15, 2007

0711.2170 (/preprints)
2007-11-15, 09:17 [edit]


[0704.2612] Relativistic Effects in Extreme Mass Ratio Gravitational Wave Bursts

Authors: Nicolas Yunes, Carlos F. Sopuerta, Louis J. Rubbo, Kelly Holley-Bockelmann

Date: 19 Apr 2007

Abstract: Extreme mass ratio bursts (EMRBs) have been proposed as a possible source for future space-borne gravitational wave detectors, such as the Laser Interferometer Space Antenna (LISA). These events are characterized by long-period, nearly-radial orbits of compact objects around a central massive black hole. The gravitational radiation emitted during such events consists of a short burst, corresponding to periapse passage, followed by a longer, silent interval. In this paper we investigate the impact of including relativistic corrections to the description of the compact object's trajectory via a geodesic treatment, as well as including higher-order multipole corrections in the waveform calculation. The degree to which the relativistic corrections are important depends on the EMRB's orbital parameters. We find that relativistic EMRBs (v_{max}}/c > 0.25) are not rare and actually account for approximately half of the events in our astrophysical model. The relativistic corrections tend to significantly change the waveform amplitude and phase relative to a Newtonian description, although some of this dephasing could be mimicked by parameter errors. The dephasing over several bursts could be of particular importance not only to gravitational wave detection, but also to parameter estimation, since it is highly correlated to the spin of the massive black hole. Consequently, we postulate that if a relativistic EMRB is detected, such dephasing might be used to probe the relativistic character of the massive black hole and obtain information about its spin.

abs pdf

Nov 12, 2007

0704.2612 (/preprints)
2007-11-12, 08:50 [edit]


[0711.1410] Merger of black hole and neutron star in general relativity: Tidal disruption, torus mass, and gravitational waves

Authors: Masaru Shibata, Keisuke Taniguchi

Date: 9 Nov 2007

Abstract: We systematically perform the merger simulation of black hole-neutron star (BH-NS) binaries in full general relativity, focusing on the case that the NS is tidally disrupted. We prepare BH-NS binaries in a quasicircular orbit as the initial condition in which the BH is modeled by a nonspinning moving puncture. For modeling the NS, we adopt the $\Gamma$-law equation of state with $\Gamma=2$ and the irrotational velocity field. We change the BH mass in the range $M_{\rm BH} \approx 3.3$--$4.6M_{\odot}$, while the rest mass of the NS is fixed to be $M_{*}=1.4 M_{\odot}$ (i.e., the NS mass $M_{\rm NS} \approx 1.3M_{\odot}$). The radius of the corresponding spherical NS is set in the range $R_{\rm NS} \approx 12$--15 km (i.e., the compactness $GM_{\rm NS}/R_{\rm NS}cˆ2 \approx 0.13$--0.16). We find for all the chosen initial conditions that the NS is tidally disrupted near the innermost stable circular orbit. For the model of $R_{\rm NS}=12$ km, more than 97 % of the rest mass is quickly swallowed into the BH and the resultant torus mass surrounding the BH is less than $0.04M_{\odot}$. For the model of $R_{\rm NS} \approx 14.7$ km, by contrast, the torus mass is about $0.16M_{\odot}$ for the BH mass $\approx 4M_{\odot}$. The thermal energy of the material in the torus increases by the shock heating occurred in the collision between the spiral arms, resulting in the temperature $10ˆ{10}$--$10ˆ{11}$ K. (.. omission ..) We also present gravitational waveforms during the inspiral, tidal disruption of the NS, and subsequent evolution of the disrupted material. (.. omission ..)

abs pdf

Nov 12, 2007

0711.1410 (/preprints)
2007-11-12, 08:49 [edit]


[0711.1165] Foundations of multiple black hole evolutions

Authors: Carlos O. Lousto, Yosef Zlochower

Date: 8 Nov 2007

Abstract: We present techniques for long-term, stable, and accurate evolutions of multiple-black-hole spacetimes using the ‘moving puncture’ approach with fourth- and eighth-order finite difference stencils. We use these techniques to explore configurations of three black holes in a hierarchical system consisting of a third black hole approaching a quasi-circular black-hole binary, and find that, depending on the size of the binary, the resulting encounter may lead to a prompt merger of all three black holes, production of a highly elliptical binary (with the third black hole remaining unbound), or disruption of the binary (leading to three free black holes). We also analyze the classical Burrau three-body problem using full numerical evolutions. In both cases, we find behaviors distinctly different from Newtonian predictions, which has important implications for N-body black-hole simulations. For our simulations we use analytic approximate data. We find that the eighth-order stencils significantly reduce the numerical errors for our choice of grid sizes, and that the approximate initial data produces the expected waveforms (after a rescaling of the puncture masses) for black-hole binaries with modest initial separations.

abs pdf

Nov 09, 2007

0711.1165 (/preprints)
2007-11-09, 17:12 [edit]


[0711.0750] Gravitational lensing by the supermassive black hole in the center of M31

Authors: V. Bozza, S. Calchi Novati, L. Mancini

Date: 5 Nov 2007

Abstract: We examine the possibility of observing gravitational lensing in the weak deflection regime by the supermassive black hole in the center of the galaxy M31. This black hole is significantly more massive than the black hole in the center of our Galaxy qualifying itself as a more effective lens. However, it is also more distant and the candidate stellar sources appear consequently fainter. As potential sources we separately consider stars belonging to the bulge, to the disk, to the triple nucleus formed by P1+P2 and by the recently discovered inner cluster P3. We calculate the number of simultaneously lensed stars at a given time as a function of the threshold magnitude required for the secondary image. For observations in the K-band we find 1.4 expected stars having secondary images brighter than K=24 and 182 brighter than K=30. For observations in the V-band we expect 1.3 secondary images brighter than V=27 and 271 brighter than V=33. The bulge stars have the highest chance to be lensed by the supermassive black hole, whereas the disk and the composite nucleus stars contribute by 10% each. The typical angular separation of the secondary images from the black hole range from 1 mas to 0.1''. For each population we also show the distribution of the lensed sources as a function of their distance and absolute magnitude, the expected angular positions and velocities of the generated secondary images, the rate and the typical duration of the lensing events.

abs pdf

Nov 08, 2007

0711.0750 (/preprints)
2007-11-08, 11:03 [edit]


[0711.0743] Gravitational Wave Sirens as a Triple Probe of Dark Energy

Authors: Eric V. Linder

Date: 5 Nov 2007

Abstract: Gravitational wave standard sirens have been considered as precision distance indicators to high redshift; however, at high redshift standard sirens or standard candles such as supernovae suffer from lensing noise. We investigate lensing noise as a signal instead and show how measurements of the maximum demagnification (minimum convergence) probe cosmology in a highly complementary manner to the distance itself. Revisiting the original form for minimum convergence we quantify the bias arising from the commonly used approximation. Furthermore, after presenting a new lensing probability function we discuss how the width of the lensed standard siren amplitude distribution also probes growth of structure. Thus standard sirens and candles can serve as triple probes of dark energy, measuring both the cosmic expansion history and growth history.

abs pdf

Nov 08, 2007

0711.0743 (/preprints)
2007-11-08, 11:02 [edit]


[0711.1115] Gravitational-Wave Data Analysis. Formalism and Sample Applications: The Gaussian Case

Authors: Piotr Jaranowski, Andrzej Kr&#xf3;lak

Date: 7 Nov 2007

Abstract: The article reviews the statistical theory of signal detection in application to analysis of deterministic gravitational-wave signals in the noise of a detector. Statistical foundations for the theory of signal detection and parameter estimation are presented. Several tools needed for both theoretical evaluation of the optimal data analysis methods and for their practical implementation are introduced. They include optimal signal-to-noise ratio, Fisher matrix, false alarm and detection probabilities, $\F$-statistic, template placement, and fitting factor. These tools apply to the case of signals buried in a stationary and Gaussian noise. Algorithms to efficiently implement the optimal data analysis techniques are discussed. Formulas are given for a general gravitational-wave signal that includes as special cases most of the deterministic signals of interest.

abs pdf

Nov 08, 2007

0711.1115 (/preprints)
2007-11-08, 11:02 [edit]


[0711.1048] Hamiltonian of two spinning compact bodies with next-to-leading order gravitational spin-orbit coupling

Authors: Thibault Damour, Piotr Jaranowski, Gerhard Sch&#xe4;fer

Date: 7 Nov 2007

Abstract: A Hamiltonian formulation is given for the gravitational dynamics of two spinning compact bodies to next-to-leading order ($G/cˆ4$ and $Gˆ2/cˆ4$) in the spin-orbit interaction. We use a novel approach (valid to linear order in the spins), which starts from the second-post-Newtonian metric (in ADM coordinates) generated by two spinless bodies, and computes the next-to-leading order precession, in this metric, of suitably redefined ‘constant-magnitude’ 3-dimensional spin vectors ${\bf S}_1$, ${\bf S}_2$. We prove the Poincaré invariance of our Hamiltonian by explicitly constructing ten phase-space generators realizing the Poincaré algebra. A remarkable feature of our approach is that it allows one to derive the {\it orbital} equations of motion of spinning binaries to next-to-leading order in spin-orbit coupling without having to solve Einstein's field equations with a spin-dependent stress tensor. We show that our Hamiltonian (orbital and spin) dynamics is equivalent to the dynamics recently obtained by Faye, Blanchet, and Buonanno, by solving Einstein's equations in harmonic coordinates.

abs pdf

Nov 08, 2007

0711.1048 (/preprints)
2007-11-08, 11:01 [edit]


[0711.1097] Multipolar analysis of spinning binaries

Authors: E. Berti, V. Cardoso, J. A. Gonzalez, U. Sperhake, B. Bruegmann

Date: 7 Nov 2007

Abstract: We present a preliminary study of the multipolar structure of gravitational radiation from spinning black hole binary mergers. We consider three different spinning binary configurations: (1) one "hang-up" run, where the black holes have equal masses and large spins initially aligned with the orbital angular momentum; (2) seven "spin-flip" runs, where the holes have a mass ratio q=4, the spins are anti-aligned with the orbital angular momentum, and the initial Kerr parameters of the holes j_1=j_2=j_i are fine-tuned to produce a Schwarzschild remnant after merger; (3) three "super-kick" runs where the mass ratio q=M_1/M_2=1, 2, 4 and the spins of the two holes are initially located on the orbital plane, pointing in opposite directions. For all of these simulations we compute the multipolar energy distribution and the Kerr parameter of the final hole. For the hang-up run, we show that including leading-order spin-orbit and spin-spin terms in a multipolar decomposition of the post-Newtonian waveforms improves the agreement with the numerical simulation.

abs pdf

Nov 08, 2007

0711.1097 (/preprints)
2007-11-08, 11:01 [edit]


[0711.0726] Angular Resolution of A Network of Gravitational-Wave Detectors and Localization Methods

Authors: Linqing Wen (MPI/AEI), Xilong Fan (BNU), Yanbei Chen (MPI/AEI)

Date: 5 Nov 2007

Abstract: We report for the first time a general geometrical expression for the angular resolution of an arbitrary network of interferometric gravitational wave (GW) detectors when the arrival-time of a GW is unknown. We discuss the implications of our results on how to improve angular resolutions of the network. An example of an improved localization method for GWs of unknown waveforms is demonstrated.

abs pdf

Nov 05, 2007

0711.0726 (/preprints)
2007-11-05, 18:13 [edit]


[0711.0669] Delicacy of Binary Black Hole Mergers in the Presence of Spurious Radiation

Authors: Tanja Bode, Deirdre Shoemaker, Frank Herrmann, Ian Hinder

Date: 5 Nov 2007

Abstract: We present an investigation into how sensitive the last orbits and merger of binary-black-hole systems are to the presence of spurious radiation in the initial data. Our numerical experiments consist of a binary-black-hole system starting at the last couple of orbits before merger with additional spurious radiation centered at the origin and the initial angular momentum held fixed. As the energy in the radiation increases, the binary is invariably hardened, i.e. the merger of the two black holes is hastened. The change in merger time becomes significant when the additional energy provided by the spurious radiation increases the M_ADM of the spacetime by about 1%. While the final masses of the black holes increase due to partial absorption of the radiation, the final spins remain constant to within our numerical accuracy. We conjecture that the spurious radiation is primarily increasing the eccentricity of the orbit and secondarily increasing the mass of the black holes while propagating out to infinity.

abs pdf

Nov 05, 2007

0711.0669 (/preprints)
2007-11-05, 18:12 [edit]


[0711.0302] Inspiralling compact binaries in quasi-elliptical orbits: The complete 3PN energy flux

Authors: K G Arun, Luc Blanchet, Bala R Iyer, Moh&#x27;d S S Qusailah

Date: 2 Nov 2007

Abstract: The instantaneous contributions to the 3PN gravitational wave luminosity from the inspiral phase of a binary system of compact objects moving in a quasi elliptical orbit is computed using the multipolar post-Minkowskian wave generation formalism. The necessary inputs for this calculation include the 3PN accurate mass quadrupole moment for general orbits and the mass octupole and current quadrupole moments at 2PN. Using the recently obtained 3PN quasi-Keplerian representation of elliptical orbits the flux is averaged over the binary's orbit. Supplementing this by the important hereditary contributions arising from tails, tails-of-tails and tails squared terms calculated in a previous paper, the complete 3PN energy flux is obtained. The final result presented in this paper would be needed for the construction of ready-to-use templates for binaries moving on non-circular orbits, a plausible class of sources not only for the space based detectors like LISA but also for the ground based ones.

abs pdf

Nov 05, 2007

0711.0302 (/preprints)
2007-11-05, 09:29 [edit]


[0711.0349] Adaptive multiresolution for wavelet analysis

Authors: Riccardo Sturani, Roberto Terenzi

Date: 2 Nov 2007

Abstract: We present a new method of wavelet packet decomposition to be used in gravitational wave detection. An issue in wavelet analysis is what is the time-frequency resolution which is best suited to analyze data when in quest of a signal of unknown shape, like a burst. In the other wavelet methods currently employed, like LIGO WaveBurst, the analysis is performed at some trial resolutions. We propose a decomposition which automatically selects at any frequency the best resolution. The criterion for resolution selection is based on minimization of a function of the data, named entropy in analogy with the information theory. As a qualitative application we show how a multiresolution time-frequency scalogram looks in the case of a sample signal injected over Gaussian noise. For a more quantitative application of the method we tested its efficiency as a non-linear filter of simulated data for burst searches, finding that it is able to lower the false alarm rate of the WaveBurst algorithm with negligible effects on the efficiency.

abs pdf

Nov 05, 2007

0711.0349 (/preprints)
2007-11-05, 09:29 [edit]


[0711.0273] The Emergence of Spacetime, or, Quantum Gravity on Your Desktop

Authors: R. Loll

Date: 2 Nov 2007

Abstract: Is there an approach to quantum gravity which is conceptually simple, relies on very few fundamental physical principles and ingredients, emphasizes geometric (as opposed to algebraic) properties, comes with a definite numerical approximation scheme, and produces robust results, which go beyond showing mere internal consistency of the formalism? The answer is a resounding yes: it is the attempt to construct a nonperturbative theory of quantum gravity, valid on all scales, with the technique of so-called Causal Dynamical Triangulations. Despite its conceptual simplicity, the results obtained up to now are far from trivial. Most remarkable at this stage is perhaps the fully dynamical emergence of a classical background (and solution to the Einstein equations) from a nonperturbative sum over geometries, without putting in any preferred geometric background at the outset. In addition, there is concrete evidence for the presence of a fractal spacetime foam on Planckian distance scales. The availability of a computational framework provides built-in reality checks of the approach, whose importance can hardly be overestimated.

abs pdf

Nov 05, 2007

0711.0273 (/preprints)
2007-11-05, 09:29 [edit]


[0711.0250] Tail effects in the 3PN gravitational wave energy flux of compact binaries in quasi-elliptical orbits

Authors: K G Arun, Luc Blanchet, Bala R Iyer, Moh&#x27;d S S Qusailah

Date: 2 Nov 2007

Abstract: The far-zone flux of energy contains hereditary (tail) contributions that depend on the entire past history of the source. Using the multipolar post-Minkowskian wave generation formalism, we propose and implement a semi-analytical method in the frequency domain to compute these contributions from the inspiral phase of a binary system of compact objects moving in quasi-elliptical orbits up to 3PN order. The method explicitly uses the quasi-Keplerian representation of elliptical orbits at 1PN order and exploits the doubly periodic nature of the motion to average the 3PN fluxes over the binary's orbit. Together with the instantaneous (non-tail) contributions evaluated in a companion paper, it provides crucial inputs for the construction of ready-to-use templates for compact binaries moving on quasi-elliptic orbits, an interesting class of sources for the ground based gravitational wave detectors such as LIGO and Virgo as well as space based detectors like LISA.

abs pdf

Nov 05, 2007

0711.0250 (/preprints)
2007-11-05, 09:28 [edit]


[0711.0034] A universal tool for determining the time delay and the frequency shift of light: Synge's world function

Authors: Pierre Teyssandier, Christophe Le Poncin-Lafitte, Bernard Linet

Date: 31 Oct 2007

Abstract: In almost all of the studies devoted to the time delay and the frequency shift of light, the calculations are based on the integration of the null geodesic equations. However, the above-mentioned effects can be calculated without integrating the geodesic equations if one is able to determine the bifunction $\Omega(x_A, x_B)$ giving half the squared geodesic distance between two points $x_A$ and $x_B$ (this bifunction may be called Synge's world function). In this lecture, $\Omega(x_A, x_B)$ is determined up to the order $1/cˆ3$ within the framework of the PPN formalism. The case of a stationary gravitational field generated by an isolated, slowly rotating axisymmetric body is studied in detail. The calculation of the time delay and the frequency shift is carried out up to the order $1/cˆ4$. Explicit formulae are obtained for the contributions of the mass, of the quadrupole moment and of the internal angular momentum when the only post-Newtonian parameters different from zero are $\beta$ and $\gamma$. It is shown that the frequency shift induced by the mass quadrupole moment of the Earth at the order $1/cˆ3$ will amount to $10ˆ{-16}$ in spatial experiments like the ESA's Atomic Clock Ensemble in Space mission. Other contributions are briefly discussed.

abs pdf

Nov 01, 2007

0711.0034 (/preprints)
2007-11-01, 20:20 [edit]


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