[0905.3798] Gravimetry, Relativity, and the Global Navigation Satellite Systems

Authors: Albert Tarantola, Ludek Klimes, Jose Maria Pozo, Bartolome Coll

Date: 23 May 2009

Abstract: Relativity is an integral part of positioning systems, and this is taken into account in today's practice by applying many "relativistic corrections" to computations performed using concepts borrowed from Galilean physics. A different, fully relativistic paradigm can be developed for operating a positioning system. This implies some fundamental changes. For instance, the basic coordinates are four times (with a symmetric meaning, not three space coordinate and one time coordinate) and the satellites must have cross-link capabilities. Gravitation must, of course, be taken into account, but not using the Newtonian theory: the gravitation field is, and only is, the space-time metric. This implies that the positioning problem and the gravimetry problem can not be separated. An optimization theory can be developed that, because it is fully relativistic, does not contain any "relativistic correction". We suggest that all positioning satellite systems should be operated in this way. The first benefit of doing so would be a clarification and a simplification of the theory. We also expect, at the end, to be able to run the positioning systems with increased accuracy.

abs pdf

May 27, 2009

0905.3798 (/preprints)
2009-05-27, 14:25 [edit]


[0905.4227] Status of NINJA: the Numerical INJection Analysis project

Authors: Benjamin Aylott, John G. Baker, William D. Boggs, Michael Boyle, Patrick R. Brady, Duncan A. Brown, Bernd Brügmann, Luisa T. Buchman, Alessandra Buonanno, Laura Cadonati, Jordan Camp, Manuela Campanelli, Joan Centrella, Shourov Chatterjis, Nelson Christensen, Tony Chu, Peter Diener, Nils Dorband, Zachariah B. Etienne, Joshua Faber, Stephen Fairhurst, Benjamin Farr, Sebastian Fischetti, Gianluca Guidi, Lisa M. Goggin, Mark Hannam, Frank Herrmann, Ian Hinder, Sascha Husa, Vicky Kalogera, Drew Keppel, Lawrence E. Kidder, Bernard J. Kelly, Badri Krishnan, Pablo Laguna, Carlos O. Lousto, Ilya Mandel, Pedro Marronetti, Richard Matzner, Sean T. McWilliams, Keith D. Matthews, R. Adam Mercer, Satyanarayan R. P. Mohapatra, Abdul H. Mroue;, Hiroyuki Nakano, Evan Ochsner, Yi Pan, Larne Pekowsky, Harald P. Pfeiffer, Denis Pollney, Frans Pretorius, Vivien Raymond, Christian Reisswig, Luciano Rezzolla, Oliver Rinne, Craig Robinson, Christian Roever, Lucia Santamaria, Bangalore Sathyaprakash, Mark A. Scheel, Erik Schnetter, Jennifer Seiler, Stuart L. Shapiro, Deirdre Shoemaker, Ulrich Sperhake, Alexander Stroeer, Riccardo Sturani, Wolfgang Tichy, Yuk Tung Liu, Marc van der Sluys, James R. van Meter, Ruslan Vaulin, Alberto Vecchio, John Veitch, Andrea Vicere, John T. Whelan, Yosef Zlochower

Date: 26 May 2009

Abstract: The 2008 NRDA conference introduced the Numerical INJection Analysis project (NINJA), a new collaborative effort between the numerical relativity community and the data analysis community. NINJA focuses on modeling and searching for gravitational wave signatures from the coalescence of binary system of compact objects. We review the scope of this collaboration and the components of the first NINJA project, where numerical relativity groups shared waveforms and data analysis teams applied various techniques to detect them when embedded in colored Gaussian noise.

abs pdf

May 27, 2009

0905.4227 (/preprints)
2009-05-27, 14:24 [edit]


[0905.3914] Final Mass and Spin of Merged Black Holes and the Golden Black Hole

Authors: James Healy, Pablo Laguna, Richard A. Matzner, Deirdre M. Shoemaker

Date: 24 May 2009

Abstract: We expand our recent study of scattering/hyperbolic mergers of equal mass black holes to include spinning holes and to consider a broader range of initial orbital angular momentum. These encounters are plunge coalescences aimed at minimizing angular momentum radiation losses during the merger, thus maximizing the final spin of the merged black hole. For the optimal case of initial black holes with spins aligned with the orbital angular momentum, we find that the final spin of the black hole can reach a maximum spin a/M_h = 0.98 when extrapolated to maximal spinning merging black holes. We also find that as one approaches the merger/no-merger threshold the encounters produce a golden black hole whose mass M_h/M and spin a/M_h depend on the total initial spin of the merging black holes but not on the initial orbital angular momentum configuration. Furthermore, solutions approaching the golden black hole limit track a spiral in the mass-spin plane of parameters of the final black hole.

abs pdf

May 27, 2009

0905.3914 (/preprints)
2009-05-27, 14:24 [edit]


[0905.4121] Using pulsars to define space-time coordinates

Authors: Bartolome Coll, Albert Tarantola

Date: 26 May 2009

Abstract: Fully relativistic coordinates have been proposed for (relativistically) running a "GPS" system. These coordinates are the arrival times of the light signals emitted by four "satellites" (clocks). Replacing the signals emitted by four controlled clocks by the signals emitted by four pulsars defines a coordinate system with lower accuracy, but valid across the whole Solar System. We here precisely define this new coordinate system, by choosing four particular pulsars and a particular event as the origin of the coordinates.

abs pdf

May 27, 2009

0905.4121 (/preprints)
2009-05-27, 14:23 [edit]


[0905.2984] Wavelet entropy filter and cross-correlation of gravitational wave data

Authors: R. Terenziand, R. Sturani

Date: 18 May 2009

Abstract: We present a method for enhancing the cross-correlation of gravitational wave signals eventually present in data streams containing otherwise uncorrelated noise. Such method makes use of the wavelet decomposition to cast the cross-correlation time series in time-frequency space. Then an entropy criterion is applied to identify the best time frequency resolution, i.e. the resolution allowing to concentrate the signal in the smallest number of wavelet coefficients. By keeping only the coefficients above a certain threshold, it is possible to reconstruct a cross-correlation time series where the effect of common signal is stronger. We tested our method against signals injected over two data streams of uncorrelated white noise.

abs pdf

May 22, 2009

0905.2984 (/preprints)
2009-05-22, 09:12 [edit]


[0905.3120] A burst search for gravitational waves from binary black holes

Authors: C. Pankow, S. Klimenko, G. Mitselmakher, I. Yakushin, G. Vedovato, M. Drago, R. A. Mercer, P. Ajith

Date: 19 May 2009

Abstract: Compact binary coalescence (CBC) is one of the most promising sources of gravitational waves. These sources are usually searched for with matched filters which require accurate calculation of the GW waveforms and generation of large template banks. We present a complementary search technique based on algorithms used in un-modeled searches. Initially designed for detection of un-modeled bursts, which can span a very large set of waveform morphologies, the search algorithm presented here is constrained for targeted detection of the smaller subset of CBC signals. The constraint is based on the assumption of elliptical polarisation for signals received at the detector. We expect that the algorithm is sensitive to CBC signals in a wide range of masses, mass ratios, and spin parameters. In preparation for the analysis of data from the fifth LIGO-Virgo science run (S5), we performed preliminary studies of the algorithm on test data. We present the sensitivity of the search to different types of simulated CBC waveforms. Also, we discuss how to extend the results of the test run into a search over all of the current LIGO-Virgo data set.

abs pdf

May 22, 2009

0905.3120 (/preprints)
2009-05-22, 09:12 [edit]


[0905.2976] Studying stellar binary systems with the Laser Interferometer Space Antenna using Delayed Rejection Markov chain Monte Carlo methods

Authors: Miquel Trias, Alberto Vecchio, John Veitch

Date: 18 May 2009

Abstract: Bayesian analysis of LISA data sets based on Markov chain Monte Carlo methods has been shown to be a challenging problem, in part due to the complicated structure of the likelihood function consisting of several isolated local maxima that dramatically reduces the efficiency of the sampling techniques. Here we introduce a new fully Markovian algorithm, a Delayed Rejection Metropolis-Hastings Markov chain Monte Carlo method, to efficiently explore these kind of structures and we demonstrate its performance on selected LISA data sets containing a known number of stellar-mass binary signals embedded in Gaussian stationary noise.

abs pdf

May 22, 2009

0905.2976 (/preprints)
2009-05-22, 09:12 [edit]


[0905.3177] Extrapolating gravitational-wave data from numerical simulations

Authors: Michael Boyle, Abdul H. Mroué

Date: 19 May 2009

Abstract: Two complementary techniques are developed for obtaining the asymptotic form of gravitational-wave data at large radii from numerical simulations, in the form of easily implemented algorithms. It is shown that, without extrapolation, near-field effects produce errors in extracted waveforms that can significantly affect LIGO data analysis. The extrapolation techniques are discussed in the context of Newman-Penrose data applied to extrapolation of waveforms from an equal-mass, nonspinning black-hole binary simulation. The results of the two methods are shown to agree within error estimates. The various benefits and deficiencies of the methods are discussed.

abs pdf

May 22, 2009

0905.3177 (/preprints)
2009-05-22, 09:12 [edit]


[0905.3537] Relativistic reactions visualized through right triangles in space

Authors: Theocharis A. Apostolatos

Date: 21 May 2009

Abstract: In this article we exploit the fact that the special relativistic formula which relates the energy and the 3-momentum of an elementary particle with its rest mass, resembles the pythagorean theorem for right triangles. Using such triangles, suitably arranged, we can prove all kind of equalities or inequalities concerning the kinematical properties of elementary particles in a wide variety of cases regarding particles' collision, decay or production. Moreover, relations that are somehow hard to produce by the usual analytic methods arise much more naturally through geometric constructions based on right triangles.

abs pdf

May 22, 2009

0905.3537 (/preprints)
2009-05-22, 09:08 [edit]


[0905.1908] Integrated Sachs-Wolfe Effect for Gravitational Radiation

Authors: Pablo Laguna, Shane L. Larson, David Spergel, Nicolas Yunes

Date: 12 May 2009

Abstract: Gravitational waves are messengers carrying valuable information about their sources. For sources at cosmological distances, the waves will contain also the imprint left by the intervening matter. The situation is in close analogy with cosmic microwave photons, for which the large-scale structures the photons traverse contribute to the observed temperature anisotropies, in a process known as the integrated Sachs-Wolfe effect. We derive the gravitational wave counterpart of this effect for waves propagating on a Friedman-Robertson-Walker background with scalar perturbations. We find that the phase, frequency and amplitude of the gravitational waves experience Sachs-Wolfe type integrated effects, this in addition to the magnification effects on the amplitude from gravitational lensing. We show that for supermassive black hole binaries, the integrated effects could account for measurable changes on the frequency, chirp mass and luminosity distance of the binary, thus unveiling the presence of inhomogeneities, and potentially dark energy, in the Universe.

abs pdf

May 19, 2009

0905.1908 (/preprints)
2009-05-19, 08:55 [edit]


[0905.1785] The search for spinning black hole binaries using a genetic algorithm

Authors: Antoine Petiteau, Shang Yu, Stanislav Babak

Date: 12 May 2009

Abstract: We use a genetic algorithm to analyze the data from the third round of the mock LISA data challenge. These data consist of gaussian stationary instrumental noise, a Galactic background and four to six signals from the inspiralling spinning BHs in quasi-circular orbits. We present a particular implementation of the genetic algorithm which uses properties of the signal and the response function. We discuss the results of a preliminary search for a single signal in the instrumental noise.

abs pdf

May 19, 2009

0905.1785 (/preprints)
2009-05-19, 08:54 [edit]


[0905.1705] Einstein@Home search for periodic gravitational waves in early S5 LIGO data

Authors: LIGO Scientific Collaboration

Date: 11 May 2009

Abstract: This paper reports on an all-sky search for periodic gravitational waves from sources such as deformed isolated rapidly-spinning neutron stars. The analysis uses 840 hours of data from 66 days of the fifth LIGO science run (S5). The data was searched for quasi-monochromatic waves with frequencies f in the range from 50 Hz to 1500 Hz, with a linear frequency drift \dot{f} (measured at the solar system barycenter) in the range -f/\tau < \dot{f} < 0.1 f/\tau, for a minimum spin-down age \tau of 1000 years for signals below 400 Hz and 8000 years above 400 Hz. The main computational work of the search was distributed over approximately 100000 computers volunteered by the general public. This large computing power allowed the use of a relatively long coherent integration time of 30 hours while searching a large parameter space. This search extends Einstein@Home's previous search in LIGO S4 data to about three times better sensitivity. No statistically significant signals were found. In the 125 Hz to 225 Hz band, more than 90% of sources with dimensionless gravitational-wave strain tensor amplitude greater than 3e-24 would have been detected.

abs pdf

May 19, 2009

0905.1705 (/preprints)
2009-05-19, 08:54 [edit]


[0905.2000] J-transform applied to the detection of Gravitational Waves: preliminary results

Authors: Daniel Bessis, Luca Perotti

Date: 13 May 2009

Abstract: We propose to apply to the detection of Gravitational Waves a new method developed for the spectral analysis of noisy time-series of damped oscillators.
From the Padé Approximations of the time-series Z-transform, a Jacobi Matrix (J-Matrix) is constructed. We show that the J-Matrix has bound states with eigenvalues strictly inside the unit circle. Each bound state can be identified with one precise damped oscillator. Beside these bound states, there is an essential spectrum sitting on the unit circle which represents the noise. In this picture, signal and noise are clearly separated and identified in the complex plane. Furthermore, we show that the J-transform enjoys the exceptional feature of lossless undersampling. We take advantage of the above properties of the J-transform to develop a procedure for the search of Gravitational Wave bursts in interferometric data series such as those of LIGO and VIRGO projects. Successful application of our procedure to simulated data having a poor signal to noise ratio, highlights the power of our method.

abs pdf

May 19, 2009

0905.2000 (/preprints)
2009-05-19, 08:51 [edit]


[0905.2502] Interferometric detection of gravitational waves: the definitive test for General Relativity

Authors: Christian Corda

Date: 15 May 2009

Abstract: Even if Einstein's General Relativity achieved a great success and overcame lots of experimental tests, it also showed some shortcomings and flaws which today advise theorists to ask if it is the definitive theory of gravity. In this essay we show that, if advanced projects on the detection of Gravitational Waves (GWs) will improve their sensitivity, allowing to perform a GWs astronomy, accurate angular and frequency dependent response functions of interferometers for GWs arising from various Theories of Gravity, i.e. General Relativity and Extended Theories of Gravity, will be the definitive test for General Relativity. The papers which found this essay have been the world's most cited in the official Astroparticle Publication Review of ASPERA during the 2007 with 13 citations.

abs pdf

May 19, 2009

0905.2502 (/preprints)
2009-05-19, 08:51 [edit]


[0905.2508] Direct Detection of the Primordial Inflationary Gravitational Waves

Authors: Wei-Tou Ni

Date: 15 May 2009

Abstract: Inflationary cosmology is successful in explaining a number of outstanding cosmological issues including the flatness, the horizon and the relic issues. More spectacular is the experimental confirmation of the structure as arose from the inflationary quantum fluctuations. However, the physics in the inflationary era is unclear. Polarization observations of Cosmic Microwave Background (CMB) missions may detect the tensor mode effects of inflationary gravitational waves (GWs) and give an energy scale of inflation. To probe the inflationary physics, direct observation of gravitational waves generated in the inflationary era is needed. In this essay, we advocate that the direct observation of these GWs with sensitivity Omega-gw down to 10**(-23) is possible using present projected technology development if foreground could be separated.

abs pdf

May 19, 2009

0905.2508 (/preprints)
2009-05-19, 08:50 [edit]


[0905.2572] Robust estimation of the parameters of a disturbed non-stationary Gaussian process

Authors: Sergio Frasca, Pia Astone

Date: 15 May 2009

Abstract: A typical problem in the detection of the gravitational waves in the data of gravitational antennas is the non-stationarity of the Gaussian noise (and so the varying sensitivity) and the presence of big impulsive disturbances. In such conditions the estimation of the standard deviation of the Gaussian process done with a classical estimator applied after a "rough" cleaning of the big pulses often gives poor results. We propose a method based on a matched filter applied to an AR histogram of the absolute value of the data

abs pdf

May 19, 2009

0905.2572 (/preprints)
2009-05-19, 08:50 [edit]


[0905.1323] Parameter estimation for signals from compact binary inspirals injected into LIGO data

Authors: Marc van der Sluys, Ilya Mandel, Vivien Raymond, Vicky Kalogera, Christian Roever, Nelson Christensen

Date: 8 May 2009

Abstract: During the fifth science run of the Laser Interferometer Gravitational-wave Observatory (LIGO), signals modelling the gravitational waves emitted by coalescing non-spinning compact-object binaries were injected into the LIGO data stream. We analysed the data segments into which such injections were made using a Bayesian approach, implemented as a Markov-chain Monte-Carlo technique in our code SPINspiral. This technique enables us to determine the physical parameters of such a binary inspiral, including masses and spin, following a possible detection trigger. For the first time, we publish the results of a realistic parameter-estimation analysis of waveforms embedded in real detector noise. We used both spinning and non-spinning waveform templates for the data analysis and demonstrate that the intrinsic source parameters can be estimated with an accuracy of better than 1-3% in the chirp mass and 0.02-0.05 (8-20%) in the symmetric mass ratio if non-spinning waveforms are used. We also find a bias between the injected and recovered parameters, and attribute it to the difference in the post-Newtonian orders of the waveforms used for injection and analysis.

abs pdf

May 12, 2009

0905.1323 (/preprints)
2009-05-12, 12:56 [edit]


[0905.1243] Static self-gravitating many-body systems in Einstein gravity

Authors: Lars Andersson (AEI and UM), Berndt G. Schmidt (AEI)

Date: 8 May 2009

Abstract: We consider the problem of constructing static, elastic, many-body systems in Einstein gravity. The solutions constructed are deformations of static many-body configurations in Newtonian gravity. No symmetry assumptions are made.

abs pdf

May 12, 2009

0905.1243 (/preprints)
2009-05-12, 12:56 [edit]


[0905.1121] Stirring, not shaking: binary black holes' effects on electromagnetic fields

Authors: Carlos Palenzuela, Matthew Anderson, Luis Lehner, Steven L. Liebling, David Neilsen

Date: 8 May 2009

Abstract: In addition to producing gravitational waves (GW), the dynamics of a binary black hole system could induce emission of electromagnetic (EM) radiation by affecting the behavior of plasmas and electromagnetic fields in their vicinity. We here study how the electromagnetic fields are affected by a pair of orbiting black holes through the merger. In particular, we show how the binary's dynamics induce a variability in possible electromagnetically induced emissions as well as a possible enhancement of electromagnetic fields during the late-merge and merger epochs. These time dependent features will likely leave their imprint in processes generating detectable emissions and can be exploited in the detection of electromagnetic counterparts of gravitational waves.

abs pdf

May 12, 2009

0905.1121 (/preprints)
2009-05-12, 12:56 [edit]


[0905.1355] Can accretion disk properties distinguish gravastars from black holes?

Authors: Tiberiu Harko, Zolt&#xe1;n Kov&#xe1;cs, Francisco S. N. Lobo

Date: 8 May 2009

Abstract: Gravastars, hypothetic astrophysical objects, consisting of a dark energy condensate surrounded by a strongly correlated thin shell of anisotropic matter, have been proposed as an alternative to the standard black hole picture of general relativity. Observationally distinguishing between astrophysical black holes and gravastars is a major challenge for this latter theoretical model. In the context of stationary and axially symmetrical geometries, a possibility of distinguishing gravastars from black holes is through the comparative study of thin accretion disks around rotating gravastars and Kerr-type black holes, respectively. In the present paper, we consider accretion disks around slowly rotating gravastars, with all the metric tensor components estimated up to the second order in the angular velocity. Due to the differences in the exterior geometry, the thermodynamic and electromagnetic properties of the disks (energy flux, temperature distribution and equilibrium radiation spectrum) are different for these two classes of compact objects, consequently giving clear observational signatures. In addition to this, it is also shown that the conversion efficiency of the accreting mass into radiation is always smaller than the conversion efficiency for black holes, i.e., gravastars provide a less efficient mechanism for converting mass to radiation than black holes. Thus, these observational signatures provide the possibility of clearly distinguishing rotating gravastars from Kerr-type black holes.

abs pdf

May 12, 2009

0905.1355 (/preprints)
2009-05-12, 12:54 [edit]


[0905.0687] Feasibility of measuring the Shapiro time delay over meter-scale distances

Authors: S. Ballmer (LIGO-Caltech), S. M&#xe1;rka (Columbia University), P. Shawhan (University of Maryland)

Date: 5 May 2009

Abstract: The time delay of light as it passes by a massive object, first calculated by Shapiro in 1964, is a hallmark of the curvature of space-time. To date, all measurements of the Shapiro time delay have been made over solar-system distance scales. We show that the new generation of kilometer-scale laser interferometers being constructed as gravitational wave detectors, in particular Advanced LIGO, will in principle be sensitive enough to measure variations in the Shapiro time delay produced by a suitably designed rotating object placed near the laser beam. We show that such an apparatus is feasible (though not easy) to construct, present an example design, and calculate the signal that would be detectable by Advanced LIGO. This offers the first opportunity to measure space-time curvature effects on a laboratory distance scale.

abs pdf

May 07, 2009

0905.0687 (/preprints)
2009-05-07, 09:23 [edit]


[0905.0020] Search for gravitational-wave bursts in the first year of the fifth LIGO science run

Authors: LIGO Scientific Collaboration: B. P. Abbott, et al

Date: 1 May 2009

Abstract: We present the results obtained from an all-sky search for gravitational-wave (GW) bursts in the 64-2000 Hz frequency range in data collected by the LIGO detectors during the first year (November 2005 - November 2006) of their fifth science run. The total analyzed livetime was 268.6 days. Multiple hierarchical data analysis methods were invoked in this search. The overall sensitivity expressed in terms of the root-sum-square (rss) strain amplitude h_{rss} for gravitational-wave bursts with various morphologies was in the range of 6 times 10ˆ{-22} Hzˆ{-½} to a few times 10ˆ{-21} Hzˆ{-½}. No GW signals were observed and a frequentist upper limit of 3.6 events per year on the rate of strong GW bursts was placed at the 90% confidence level. As in our previous searches, we also combined this rate limit with the detection efficiency for selected waveform morphologies to obtain event rate versus strength exclusion curves. In sensitivity, these exclusion curves are the most stringent to date.

abs pdf

May 04, 2009

0905.0020 (/preprints)
2009-05-04, 17:13 [edit]


[0904.4848] How photon astronomy affects searches for continuous gravitational waves

Authors: Benjamin J. Owen (Penn State)

Date: 30 Apr 2009

Abstract: Due to their computational limitations, searches for continuous gravitational waves (GW) are significantly more sensitive when informed by observational photon astronomy and theoretical astrophysics. Indirect upper limits on GW emission inferred from photon astronomy indicate which objects are more interesting for GW searches, and also set sensitivity milestones which GW searches need to beat to be considered GW astronomy. How GW results are interpreted depends on previous indirect limits and the theory of astrophysical GW emission mechanisms. I describe the interplay between these issues for the four types of continuous GW search, and show how photon astronomers can help the growing field of GW astronomy now and in the near future.

abs pdf

May 01, 2009

0904.4848 (/preprints)
2009-05-01, 13:19 [edit]


[0904.4910] Search for High Frequency Gravitational Wave Bursts in the First

Authors: LIGO Scientific Collaboration: B. Abbott, et al

Date: 30 Apr 2009

Abstract: We present an all-sky search for gravitational waves in the frequency range 1 to 6 kHz during the first calendar year of LIGO's fifth science run. This is the first untriggered LIGO burst analysis to be conducted above 3 kHz. We discuss the unique properties of interferometric data in this regime. 161.3 days of triple-coincident data were analyzed. No gravitational events above threshold were observed and a frequentist upper limit of 5.4 events per year on the rate of strong gravitational wave bursts was placed at a 90% confidence level. Implications for specific theoretical models of gravitational wave emission are also discussed.

abs pdf

May 01, 2009

0904.4910 (/preprints)
2009-05-01, 13:17 [edit]


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