## [gr-qc/0604080] Performing a theoretically robust Ryan test using intermediate-mass black holes

Authors: James S. Graber

Date: Thu, 27 Apr 2006

Abstract: We investigate the possibility of using binary IMBH inspirals to perform the Ryan test of general relativity in a theoretically robust manner using data from early in the detectable part of the inspiral. We find this to be feasible and compute the masses of the most favourable systems.

#### Apr 28, 2006

0604080 (/preprints/gr-qc)
2006-04-28, 08:24 

## Experiments on Random Packings of Ellipsoids

Phys. Rev. Lett. 94, 198001 (2005)

Experiments on Random Packings of Ellipsoids

Weining Man, Aleksandar Donev, Frank H. Stillinger, Matthew T. Sullivan, William B. Russel, David Heeger, Souheil Inati, Salvatore Torquato, and P. M. Chaikin

#### Apr 25, 2006

packings (/preprints)
2006-04-25, 11:55 

## [gr-qc/0604067] Probing the non-linear structure of general relativity with black hole mergers

Authors: K.G. Arun, B.R. Iyer, M.S.S. Qusailah, B.S. Sathyaprakash

Date: Sun, 16 Apr 2006

Abstract: Observations of the inspiral of massive binary black holes (BBH) in the Laser Interferometer Space Antenna (LISA) and stellar mass binary black holes in the European Gravitational-Wave Observatory (EGO) offer an unique opportunity to test the non-linear structure of general relativity. For a binary composed of two non-spinning black holes, the non-linear general relativistic effects depend only on the masses of the constituents. In a recent letter, we explored the possibility of a test to determine all the post-Newtonian coefficients in the gravitational wave-phasing. However, mutual covariances dilute the effectiveness of such a test. In this communication, we propose a more powerful test in which the various post-Newtonian coefficients in the gravitational wave phasing are systematically measured by treating three of them as independent parameters and demanding their mutual consistency. LISA (EGO) will observe BBH inspirals with a signal-to-noise ratio of more than 1000 (100) and thereby test the self-consistency of each of the nine post-Newtonian coefficients that have so-far been computed, by measuring the lower order coefficients to a relative accuracy of $\sim 10ˆ{-5}$ (respectively, $\sim 10ˆ{-4}$) and the higher order coefficients to a relative accuracy in the range $10ˆ{-4}$-0.1 (respectively, $10ˆ{-3}$-1).

#### Apr 18, 2006

0604067 (/preprints/gr-qc)
2006-04-18, 09:27 

## [gr-qc/0604064] Half century of black-hole theory: from physicists' purgatory to mathematicians' paradise

Authors: Brandon Carter

Date: Sat, 15 Apr 2006

Abstract: Although implicit in the discovery of the Schwarzschild solution 40 years earlier, the issues raised by the theory of what are now known as black holes were so unsettling to physicists of Einstein's generation that the subject remained in a state of semiclandestine gestation until his demise. That turning point -- just half a century after Einstein's original foundation of relativity theory, and just half a century ago today -- can be considered to mark the birth of black hole theory as a subject of systematic development by physicists of a new and less inhibited generation, whose enthusastic investigations have revealed structures of unforeseen mathematical beauty, even though questions about the physical significance of the concomitant singularities remain controversial.

#### Apr 18, 2006

0604064 (/preprints/gr-qc)
2006-04-18, 09:27 

## [gr-qc/0604037] temporar[il]y suspended

Authors: S. Babak, R. Balasubramanian, D. Churches, T. Cokelaer, B. S. Sathyaprakash

Date: Thu, 13 Apr 2006

Abstract: This paper has been withdrawn temporary by the author due to some comments to be taken into account.

#### Apr 13, 2006

0604037 (/preprints/gr-qc)
2006-04-13, 21:41 

## [gr-qc/0604032] Binary black hole detection rates in inspiral gravitational wave searches

Authors: Chris Van Den Broeck

Date: Fri, 7 Apr 2006

Abstract: The signal-to-noise ratios (SNRs) for binary black hole inspirals computed from restricted post-Newtonian waveforms are compared with those attained by more complete post-Newtonian signals, which are superpositions of amplitude-corrected harmonics of the orbital phase. It is shown that modeling signals as restricted waveforms can lead to a large overestimation of SNRs, and hence of detection rates. The effect results entirely from the absence of amplitude corrections to the dominant harmonic. By reinstating these, it is possible to construct reliable waveforms for simulated signals without having to include higher harmonics.

#### Apr 10, 2006

0604032 (/preprints/gr-qc)
2006-04-10, 09:52 

## [gr-qc/0604017] Detecting Highly Oscillatory Signals by Chirplet Path Pursuit

Authors: Emmanuel J. Candes, Philip R. Charlton, Hannes Helgason

Date: Wed, 5 Apr 2006

Abstract: This paper considers the problem of detecting nonstationary phenomena, and chirps in particular, from very noisy data. Chirps are waveforms of the very general form A(t) exp(i\lambda \phi(t)), where \lambda is a (large) base frequency, the phase \phi(t) is time-varying and the amplitude A(t) is slowly varying. Given a set of noisy measurements, we would like to test whether there is signal or whether the data is just noise. One particular application of note in conjunction with this problem is the detection of gravitational waves predicted by Einstein's Theory of General Relativity.
We introduce detection strategies which are very sensitive and more flexible than existing feature detectors. The idea is to use structured algorithms which exploit information in the so-called chirplet graph to chain chirplets together adaptively as to form chirps with polygonal instantaneous frequency. We then search for the path in the graph which provides the best trade-off between complexity and goodness of fit. Underlying our methodology is the idea that while the signal may be extremely weak so that none of the individual empirical coefficients is statistically significant, one can still reliably detect by combining several coefficients into a coherent chain. This strategy is general and may be applied in many other detection problems. We complement our study with numerical experiments showing that our algorithms are so sensitive that they seem to detect signals whenever their strength makes them detectable.

#### Apr 05, 2006

0604017 (/preprints/gr-qc)
2006-04-05, 22:25 

## [gr-qc/0604018] Testing post-Newtonian theory with gravitational wave observations

Authors: K.G. Arun, B.R. Iyer, M.S.S. Qusailah, B.S. Sathyaprakash

Date: Wed, 5 Apr 2006

Abstract: The Laser Interferometric Space Antenna (LISA) will observe supermassive black hole binary mergers with amplitude signal-to-noise ratio of several thousands. We investigate the extent to which such observations afford high-precision tests of Einstein's gravity. We show that LISA provides a unique opportunity to probe the non-linear structure of post-Newtonian theory both in the context of general relativity and its alternatives.

#### Apr 05, 2006

0604018 (/preprints/gr-qc)
2006-04-05, 22:25 

## [gr-qc/0604012] Gravitational radiation from spinning-black-hole binaries: The orbital hang up

Authors: M. Campanelli, C. O. Lousto, Y. Zlochower

Date: Tue, 4 Apr 2006

Abstract: We study the dynamics of spinning-black-hole binaries by numerically solving the full nonlinear field equations of General Relativity. We compute trajectories, merger times, and radiation waveforms. We find that the last stages of the orbital motion of black-hole binaries are profoundly affected by the individual spins. In order to cleanly display its effects, we consider two equal mass holes with individual spin parameters S/mˆ2=0.75, both aligned and anti-aligned with the orbital angular momentum. We choose initial data corresponding to quasicircular orbits with a period of 125M for both cases. The computed merger time for the aligned spin case is ~225M, performing nearly three orbits before merger, while for the anti-aligned case the merger time is \~105M, performing just less than one orbit before merger. The total energy radiated for the former case is ~6% while for the latter it is only ~2%. The final Kerr hole remnants have rotation parameters a/M=0.9 and a/M=0.44 respectively, showing the difficulty of creating a maximally rotating black hole out of the merger of two spinning holes.

#### Apr 04, 2006

0604012 (/preprints/gr-qc)
2006-04-04, 19:19 

## [gr-qc/0604005] Rank deficiency and Tikhonov regularization in the inverse problem for gravitational-wave bursts

Authors: M. Rakhmanov

Date: Mon, 3 Apr 2006

Abstract: Coherent searches for gravitational-wave bursts rely on methods which combine data from several detectors taking into account differences in their responses. The efforts are now focused on the maximum likelihood principle as the most natural way to combine data, which can also be used without prior knowledge of the signal. Recent studies however have shown that straightforward application of the maximum likelihood method to gravitational waves with unknown waveforms can lead to inconsistencies and unphysical results, such as the discontinuity in the functional form of residual or the divergence of the variance of the estimated solution for some locations in the sky. Several solutions to these problems based on different physical arguments have been proposed so far. In this paper we continue these investigations and show from a very general point of view that the detection of gravitational-wave bursts with a network of detectors belongs to the category of ill-posed problems, i.e. discrete inverse problem with rank-deficient matrix. We describe how to apply Tikhonov regularization technique to resolve the rank deficiency. A variant of Tikhonov regulator which minimizes the condition number of the matrix for all locations in the sky is introduced and its application for burst searches is briefly discussed.

#### Apr 04, 2006

0604005 (/preprints/gr-qc)
2006-04-04, 09:32