http://www.vallis.org/blogspace My Experimental Blosxom Weblog. en http://www.vallis.org/blogspace/2008/11/20#0811.3006 <p class="story_para"> <b>Authors</b>: Manuela Campanelli, Carlos O. Lousto, Yosef Zlochower </p> <p class="story_para"> <b>Date</b>: 18 Nov 2008 </p> <p class="story_para"> <b>Abstract</b>: In this paper we develop a technique for determining the algebraic classification of a numerical spacetime, possibly resulting from a generic black-hole-binary merger, using the Newman-Penrose Weyl scalars. We demonstrate these techniques for a test case involving a close binary with arbitrarily oriented spins and unequal masses. We find that, post merger, the spacetime quickly approaches Petrov type II, and only approaches type D on much longer timescales. These techniques allow us to begin to explore the validity of the "no-hair theorem" for generic merging-black-hole spacetimes. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0811.3006">abs</a> <a href="http://www.arxiv.org/pdf/0811.3006">pdf</a></p> http://www.vallis.org/blogspace/2008/11/14#home <p class="story_para"> &rarr; <a href="http://www.vallis.org/blogspace/home.html">Back</a> to the wiki root </p> <p class="story_para"> <h3>Workshops and conferences:</h3> </p> <p class="story_para"> &rarr; <a href="http://www.vallis.org/blogspace/progtricks/scipy2006.html">SciPy2006</a> </p> <p class="story_para"> &rarr; <a href="http://www.vallis.org/blogspace/lisa/amaldi2007.html">GRG17/Amaldi7 2007</a> </p> <p class="story_para"> &rarr; <a href="http://www.vallis.org/blogspace/progtricks/scipy2007.html">SciPy2007</a> </p> <p class="story_para"> &rarr; <a href="http://www.vallis.org/blogspace/seminars/gwdaw12.html">GWDAW-12 (2007)</a> </p> <p class="story_para"> &rarr; <a href="http://www.vallis.org/blogspace/progtricks/scipy2008.html">SciPy2008</a> </p> <p class="story_para"> &rarr; <a href="http://www.vallis.org/blogfiles/seminars/home/NRAO2008.txt">BHs with GW and radio at NRAO (2008)</a> (<a href="http://www.cv.nrao.edu/~sransom/BHs_GWs_Radio">talks</a>)</p> http://www.vallis.org/blogspace/2008/11/13#0811.2069 <p class="story_para"> <b>Authors</b>: Thibault Damour, Bala R. Iyer, Alessandro Nagar </p> <p class="story_para"> <b>Date</b>: 13 Nov 2008 </p> <p class="story_para"> <b>Abstract</b>: We improve and generalize a resummation method of post-Newtonian multipolar waveforms from circular compact binaries introduced in Refs. \cite{Damour:2007xr,Damour:2007yf}. One of the characteristic features of this resummation method is to replace the usual {\it additive} decomposition of the standard post-Newtonian approach by a {\it multiplicative} decomposition of the complex multipolar waveform $h_{\lm}$ into several (physically motivated) factors: (i) the &lsquo;Newtonian&rsquo; waveform, (ii) a relativistic correction coming from an &lsquo;effective source&rsquo;, (iii) leading-order tail effects linked to propagation on a Schwarzschild background, (iv) a residual tail dephasing, and (v) residual relativistic amplitude corrections $f_{\lm}$. We explore here a new route for resumming $f_{\lm}$ based on replacing it by its $\ell$-th root: $\rho_{\lm}=f_{\lm}&circ;{1/\ell}$. In the extreme-mass-ratio case, this resummation procedure results in a much better agreement between analytical and numerical waveforms than when using standard post-Newtonian approximants. We then show that our best approximants behave in a robust and continuous manner as we &lsquo;deform&rsquo; them by increasing the symmetric mass ratio $\nu\equiv m_1 m_2/(m_1+m_2)&circ;2$ from 0 (extreme-mass-ratio case) to &frac14; (equal-mass case). The present paper also completes our knowledge of the first post-Newtonian corrections to multipole moments by computing ready-to-use explicit expressions for the first post-Newtonian contributions to the odd-parity (current) multipoles. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0811.2069">abs</a> <a href="http://www.arxiv.org/pdf/0811.2069">pdf</a></p> http://www.vallis.org/blogspace/2008/11/13#0811.1998 <p class="story_para"> <b>Authors</b>: Alexander Torres-Gomez, Kirill Krasnov </p> <p class="story_para"> <b>Date</b>: 12 Nov 2008 </p> <p class="story_para"> <b>Abstract</b>: We revisit a propagating torsion gravity theory obtained by introducing a field coupled to the topological term in the first-order Einstein-Cartan action. The resulting theory has second order field equations, no adjustable coupling constants, and one more propagating degree of freedom as compared to general relativity. Thus, one might suspect that it should be easily ruled out by e.g. the solar system tests. To see whether this is the case, we obtain the spherically-symmetric solution of the theory, and show that it is characterized by the usual mass and an additional parameter. To our great surprise we find that the leading order corrections to the usual Newtonian behaviour are exactly as in general relativity, and, in particular, are independent of the new parameter. Thus, the theory passes the classical gravity tests. The analysis of the global structure of the solution leads to yet another surprising feature of the theory: the spherically-symmetric solution is never a black hole. One either has a naked curvature singularity or a wormhole solution connecting two asymptotic regions. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0811.1998">abs</a> <a href="http://www.arxiv.org/pdf/0811.1998">pdf</a></p> http://www.vallis.org/blogspace/2008/11/11#home <p class="story_para"> &rarr; <a href="http://www.vallis.org/blogspace/home.html">Back</a> to the wiki root </p> <p class="story_para"> <h3>Promotional material</h3> </p> <p class="story_para"> &rarr; <a href="http://www.andreacentazzo.com/ecm">ECM project page</a>. </p> <p class="story_para"> &rarr; Caltech <a href="http://www.vallis.org/blogfiles/ecm/home/postcard-2.pdf">postcard</a>, <a href="http://mr.caltech.edu/media/Press_Releases/PR13197.html">media release</a>, <a href="http://events.caltech.edu/events/event-5781.html">Public Events listing</a>, <a href="http://www.vallis.org/blogfiles/ecm/home/cit-homepage.png">Caltech homepage entry</a>, <a href="http://www.vallis.org/blogfiles/ecm/home/CaltechToday.png">Caltech today entry</a>, <a href="http://www.vallis.org/blogfiles/ecm/home/program-page.pdf">Caltech evening program</a>. </p> <p class="story_para"> &rarr; California Tech <a href="http://www.vallis.org/blogfiles/ecm/home/ECM-Tech2.jpg">review</a>. </p> <p class="story_para"> &rarr; Blog posts: <a href="http://blogs.discovery.com/twisted_physics/2008/10/in-rotation.html">Twisted Physics</a>, <a href="http://cosmicvariance.com/2008/10/29/einsteins-cosmic-messengers">Cosmic Variance</a>. </p> <p class="story_para"> <h3>Movie sequences from Inspiral, Merger, and Ringdown.</h3> </p> <p class="story_para"> &rarr; <a href="http://www.vallis.org/ecm/sequence1.mov">Sequence 1</a> (2:09-2:35) </p> <p class="story_para"> &rarr; <a href="http://www.vallis.org/ecm/sequence2.mov">Sequence 2</a> (3:19-3:21); <a href="http://www.vallis.org/ecm/sequence2-loop.mov">looped</a> </p> <p class="story_para"> &rarr; <a href="http://www.vallis.org/ecm/sequence3.mov">Sequence 3</a> (3:41-3:52) </p> <p class="story_para"> &rarr; <a href="http://www.vallis.org/ecm/sequence4.mov">Sequence 4</a> (4:18-4:25); <a href="http://www.vallis.org/ecm/sequence4-long.mov">longer</a> (4:28) </p> <p class="story_para"> &rarr; <a href="http://www.vallis.org/ecm/still1.png">Still 1</a> (4:26) </p> http://www.vallis.org/blogspace/2008/11/08#0811.1011 <p class="story_para"> <b>Authors</b>: K. G. Arun, Stas Babak, Emanuele Berti, Neil Cornish, Curt Cutler, Jonathan Gair, Scott A. Hughes, Bala R. Iyer, Ryan N. Lang, Ilya Mandel, Edward K. Porter, Bangalore S. Sathyaprakash, Siddhartha Sinha, Alicia M. Sintes, Miquel Trias, Chris Van Den Broeck, Marta Volonteri </p> <p class="story_para"> <b>Date</b>: 6 Nov 2008 </p> <p class="story_para"> <b>Abstract</b>: The LISA Parameter Estimation (LISAPE) Taskforce was formed in September 2007 to provide the LISA Project with vetted codes, source distribution models, and results related to parameter estimation. The Taskforce's goal is to be able to quickly calculate the impact of any mission design changes on LISA's science capabilities, based on reasonable estimates of the distribution of astrophysical sources in the universe. This paper describes our Taskforce's work on massive black-hole binaries (MBHBs). Given present uncertainties in the formation history of MBHBs, we adopt four different population models, based on (i) whether the initial black-hole seeds are small or large, and (ii) whether accretion is efficient or inefficient at spinning up the holes. We compare four largely independent codes for calculating LISA's parameter-estimation capabilities. All codes are based on the Fisher-matrix approximation, but in the past they used somewhat different signal models, source parametrizations and noise curves. We show that once these differences are removed, the four codes give results in extremely close agreement with each other. Using a code that includes both spin precession and higher harmonics in the gravitational-wave signal, we carry out Monte Carlo simulations and determine the number of events that can be detected and accurately localized in our four population models. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0811.1011">abs</a> <a href="http://www.arxiv.org/pdf/0811.1011">pdf</a></p> http://www.vallis.org/blogspace/2008/11/08#0409054 <p class="story_para"> <b>Authors</b>: Daniele Colosi, Carlo Rovelli </p> <p class="story_para"> <b>Date</b>: 14 Sep 2004 </p> <p class="story_para"> <b>Abstract</b>: Theoretical developments related to the gravitational interaction have questioned the notion of particle in quantum field theory (QFT). For instance, uniquely-defined particle states do not exist in general, in QFT on a curved spacetime. More in general, particle states are difficult to define in a background-independent quantum theory of gravity. These difficulties have lead some to suggest that in general QFT should not be interpreted in terms of particle states, but rather in terms of eigenstates of local operators. Still, it is not obvious how to reconcile this view with the empirically-observed ubiquitous particle-like behavior of quantum fields, apparent for instance in experimental high-energy physics, or "particle"-physics. Here we offer an element of clarification by observing that already in flat space there exist --strictly speaking-- two distinct notions of particles: globally defined $n$-particle Fock-states and *local particle states*. The last describe the physical objects detected by finite-size particle detectors and are eigenstates of local field operators. In the limit in which the particle detectors are appropriately large, global and local particle states converge in a weak topology (but not in norm). This observation has little relevance for flat-space theories --it amounts to a reminder that there are boundary effects in realistic detectors--; but is relevant for gravity. It reconciles the two points of view mentioned above. More importantly, it provides a definition of local particle state that remains well-defined even when the conventional global particle states are not defined. This definition plays an important role in quantum gravity. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/gr-qc/0409054">abs</a> <a href="http://www.arxiv.org/pdf/gr-qc/0409054">pdf</a></p> http://www.vallis.org/blogspace/2008/11/07#0810.3235 <p class="story_para"> <b>Authors</b>: Julia M. Comerford, Brian F. Gerke, Jeffrey A. Newman, Marc Davis, Renbin Yan, Michael C. Cooper, S.M. Faber, David C. Koo, Alison L. Coil, D.J. Rosario </p> <p class="story_para"> <b>Date</b>: 19 Oct 2008 </p> <p class="story_para"> <b>Abstract</b>: Because structure in the Universe is built up through galaxy mergers and nearly all galaxies host a central supermassive black hole (SMBH), some galaxies should possess two SMBHs near their centers as the result of a recent merger. These SMBHs spiral to the center of the resultant merger-remnant galaxy, and one or both of the SMBHs may power active galactic nuclei (AGN). Using the DEEP2 Galaxy Redshift Survey we have examined 1881 early-type galaxies, of which 107 exhibit [O III] and Hbeta emission lines indicative of AGN activity. Of these, 37 AGN have [O III] emission-line redshifts significantly different from the redshifts of the host galaxies' stars, corresponding to velocity offsets of ~50 km/s to ~300 km/s. Two of these AGN exhibit double-peaked [O III] emission lines, while the remaining 35 AGN each exhibit a single set of velocity-offset [O III] emission lines. These AGN velocity offsets cannot be readily explained by outflows, but rather are most likely the result of recent galaxy mergers. Based on this interpretation we find that roughly half of early-type galaxies hosting AGN are also merger remnants, which implies that mergers may trigger AGN activity in early-type galaxies. Our result sets a hard lower limit of 2.0% on the fraction of early-type galaxies at redshifts 0.34 < z < 0.82 that have recently undergone mergers. We also find a merger rate of ~3 mergers/Gyr, which includes both minor and major mergers, for early-type galaxies at redshifts 0.34 < z < 0.82. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0810.3235">abs</a> <a href="http://www.arxiv.org/pdf/0810.3235">pdf</a></p> http://www.vallis.org/blogspace/2008/11/04#0810.5125 <p class="story_para"> <b>Authors</b>: Ryan N. Lang, Scott A. Hughes </p> <p class="story_para"> <b>Date</b>: 28 Oct 2008 </p> <p class="story_para"> <b>Abstract</b>: The coalescence of massive black holes is one of the primary sources of gravitational waves (GWs) for LISA. Measurements of the GWs can localize the source on the sky to an ellipse with a major axis of a few tens of arcminutes to a few degrees, depending on source redshift, and a minor axis which is 2--4 times smaller. The distance (and thus an approximate redshift) can be determined to better than a percent for the closest sources we consider, although weak lensing degrades this performance. It will be of great interest to search this three-dimensional "pixel" for an electromagnetic counterpart to the GW event. The presence of a counterpart allows unique studies which combine electromagnetic and GW information, especially if the counterpart is found prior to final merger of the holes. To understand the feasibility of early counterpart detection, we calculate the evolution of the GW pixel with time. We find that the greatest improvement in pixel size occurs in the final day before merger, when spin precession effects are maximal. The source can be localized to within 10 square degrees as early as a month before merger at $z = 1$; for higher redshifts, this accuracy is only possible in the last few days. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0810.5125">abs</a> <a href="http://www.arxiv.org/pdf/0810.5125">pdf</a></p> http://www.vallis.org/blogspace/2008/11/04#0810.5727 <p class="story_para"> <b>Authors</b>: K G Arun, Chandrakant Mishra, Chris Van Den Broeck, B R Iyer, B S Sathyaprakash, Siddhartha Sinha </p> <p class="story_para"> <b>Date</b>: 31 Oct 2008 </p> <p class="story_para"> <b>Abstract</b>: Recently it was shown that the inclusion of higher signal harmonics in the inspiral signals of binary supermassive black holes (SMBH) leads to dramatic improvements in parameter estimation with the Laser Interferometer Space Antenna (LISA). In particular, the angular resolution becomes good enough to identify the host galaxy or galaxy cluster, in which case the redshift can be determined by electromagnetic means. The gravitational wave signal also provides the luminosity distance with high accuracy, and the relationship between this and the redshift depends sensitively on the cosmological parameters, such as the equation-of-state parameter $w=p_{\rm DE}/\rho_{\rm DE}$ of dark energy. With a single binary SMBH event at $z &lt; 1$ having appropriate masses and orientation, one would be able to constrain $w$ to within a few percent. We show that, if the measured sky location is folded into the error analysis, the uncertainty on $w$ goes down by an additional factor of 2-3, leaving weak lensing as the only limiting factor in using LISA as a dark energy probe. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0810.5727">abs</a> <a href="http://www.arxiv.org/pdf/0810.5727">pdf</a></p> http://www.vallis.org/blogspace/2008/11/04#0810.5541 <p class="story_para"> <b>Authors</b>: Nicolas Yunes, David N. Spergel </p> <p class="story_para"> <b>Date</b>: 30 Oct 2008 </p> <p class="story_para"> <b>Abstract</b>: Gravitational parity violation is inherent in string theory, one effective model of which is Chern-Simons modified gravity. This effective theory introduces a parity-violating modification to the Einstein equations, whose magnitude depends on derivatives of the Chern-Simons coupling. In the dynamical formulation, this coupling is an evolving field that is sourced by spacetime curvature. We here calculate the Chern-Simons modification to the orbital evolution of a binary system of spinning compact objects in the weak-field. The ratio of the Chern-Simons correction to perigee precession to the general relativistic prediction is found to scale quadratically with the semi-major axis and inversely with the square of the object's radius. Binary pulsar systems are ideal to test this theory, since perigee precession can be measured with sub-degree accuracies and the semi-major axis is millions of times larger than the stellar radius. We find that observations of perigee precession from the double binary pulsar PSR J 0737-3039 A/B dramatically constrain the Chern-Simons coupling, M_(CS) := |\dot{\theta}|&circ;(-1) &gt; 50 meV, approximately a hundred billion times better than Solar System tests. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0810.5541">abs</a> <a href="http://www.arxiv.org/pdf/0810.5541">pdf</a></p> http://www.vallis.org/blogspace/2008/11/04#0811.0294 <p class="story_para"> <b>Authors</b>: Priscilla Canizares, Carlos F. Sopuerta (ICE, CSIC-IEEC) </p> <p class="story_para"> <b>Date</b>: 3 Nov 2008 </p> <p class="story_para"> <b>Abstract</b>: Extreme-mass-ratio inspirals (EMRIs), stellar-mass compact objects (SCOs) inspiralling into a massive black hole, are one of the main sources of gravitational waves expected for the Laser Interferometer Space Antenna (LISA). To extract the EMRI signals from the expected LISA data stream, which will also contain the instrumental noise as well as other signals, we need very accurate theoretical templates of the gravitational waves that they produce. In order to construct those templates we need to account for the gravitational backreaction, that is, how the gravitational field of the SCO affects its own trajectory. In general relativity, the backreaction can be described in terms of a local self-force, and the foundations to compute it have been laid recently. Due to its complexity, some parts of the calculation of the self-force have to be performed numerically. Here, we report on an ongoing effort towards the computation of the self-force based on time-domain multi-grid pseudospectral methods. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0811.0294">abs</a> <a href="http://www.arxiv.org/pdf/0811.0294">pdf</a></p> http://www.vallis.org/blogspace/2008/11/04#0810.5707 <p class="story_para"> <b>Authors</b>: Ik Siong Heng </p> <p class="story_para"> <b>Date</b>: 31 Oct 2008 </p> <p class="story_para"> <b>Abstract</b>: This paper introduces the use of Principal Component Analysis as a method to decompose the waveform catalogues to produce a set of orthonormal basis vectors. We apply this method to a set of supernova waveforms and compare the basis vectors obtained with those obtained through Gram-Schmidt decomposition. We observe that, for the chosen set of waveforms, the performance of the two methods are comparable for minimal match requirements up to 0.9, with 14 Gram-Schmidt basis vectors and 12 principal components required for a minimal match of 0.9. This implies that there are many common features in the chosen waveforms. Additionally, we observe the chosen waveforms have very similar features and a minimal match of 0.7 can be obtained by decomposing only one third of the entire set of waveforms in the chosen catalogue. We discuss the implications of this observation and the advantages of eigen-decomposing waveform catalogues with Principal Component Analysis. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0810.5707">abs</a> <a href="http://www.arxiv.org/pdf/0810.5707">pdf</a></p> http://www.vallis.org/blogspace/2008/11/04#0811.0188 <p class="story_para"> <b>Authors</b>: Jonathan R Gair </p> <p class="story_para"> <b>Date</b>: 2 Nov 2008 </p> <p class="story_para"> <b>Abstract</b>: One of the most exciting potential sources of gravitational waves for the Laser Interferometer Space Antenna (LISA) are the inspirals of approximately stellar mass compact objects into massive black holes in the centres of galaxies - extreme mass ratio inspirals (EMRIs). LISA should observe between a few tens and a few hundred EMRIs over the mission lifetime, mostly at low redshifts (z &lt; 1). Each observation will provide a measurement of the parameters of the host system to unprecendented precision. LISA EMRI observations will thus offer a new and unique way to probe black holes at low redshift. In this article we provide a description of the population of EMRI events that LISA is likely to observe, and how the numbers of events vary with changes in the underlying assumptions about the black hole population. We also provide fitting functions that characterise LISA's ability to detect EMRIs and which will allow LISA event rates to be computed for arbitrary population models. We finish with a discussion of an ongoing programme that will use these results to assess what constraints LISA observations could place on galaxy evolution models. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0811.0188">abs</a> <a href="http://www.arxiv.org/pdf/0811.0188">pdf</a></p> http://www.vallis.org/blogspace/2008/11/04#0811.0138 <p class="story_para"> <b>Authors</b>: Ilya Mandel, Jonathan R. Gair </p> <p class="story_para"> <b>Date</b>: 2 Nov 2008 </p> <p class="story_para"> <b>Abstract</b>: Gravitational waves emitted during intermediate-mass-ratio inspirals (IMRIs) of intermediate-mass black holes (IMBHs) into supermassive black holes could represent a very interesting source for LISA. Similarly, IMRIs of stellar-mass compact objects into IMBHs could be detectable by Advanced LIGO. At present, however, it is not clear what waveforms could be used for IMRI detection, since the post-Newtonian approximation breaks down as an IMRI approaches the innermost stable circular orbit, and perturbative solutions are only known to the lowest order in the mass ratio. We discuss the expected mismatches between approximate and true waveforms, and the choice of the best available waveform as a function of the mass ratio and the total mass of the system. We also comment on the significance of the spin of the smaller body and the need for its inclusion in the waveforms. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0811.0138">abs</a> <a href="http://www.arxiv.org/pdf/0811.0138">pdf</a></p> http://www.vallis.org/blogspace/2008/11/04#0811.0181 <p class="story_para"> <b>Authors</b>: Nicolas Yunes, Lee Samuel Finn </p> <p class="story_para"> <b>Date</b>: 2 Nov 2008 </p> <p class="story_para"> <b>Abstract</b>: All modern routes leading to a quantum theory of gravity -- i.e., perturbative quantum gravitational one-loop exact correction to the global chiral current in the standard model, string theory, and perhaps even loop quantum gravity -- require supplementing the Einstein-Hilbert action with a parity-violating Chern-Simons term. Such a term leads to amplitude-birefringent gravitational wave propagation: i.e., one (circular) polarization state amplified with propagation while the other is attenuated. The proposed Laser Interferometer Space Antenna (LISA) is capable of observing gravitational wave sources at cosmological distances, suggesting the possibility that LISA observations may place a strong bound on this manifestation of quantum gravity. Here we report on a calculation of the effect that spacetime amplitude birefringence has on the signal LISA is capable of observing from inspiraling supermassive black hole binaries at large redshift. We find that the birefringence manifests itself in the observations as an anomalous precession of the binary's orbital angular momentum as it evolves toward coalescence, whose magnitude depends on the integrated history of the Chern-Simons coupling over the worldline of radiation wavefront. We estimate that LISA could place bounds on Chern-Simons modified gravity that are several orders of magnitude stronger than the present Solar System constraints, thus providing a probe of the quantum structure of spacetime. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0811.0181">abs</a> <a href="http://www.arxiv.org/pdf/0811.0181">pdf</a></p> http://www.vallis.org/blogspace/2008/10/30#0810.5262 <p class="story_para"> <b>Authors</b>: Sergey S. Kokarev </p> <p class="story_para"> <b>Date</b>: 29 Oct 2008 </p> <p class="story_para"> <b>Abstract</b>: Within some reasonable approximations we calculate deformation of an elastic bar, falling on the source of central gravitational field. We consider both elastic deformations and plastic flow together with destroying of the bar. Concrete calculations for a number of materials are presented. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0810.5262">abs</a> <a href="http://www.arxiv.org/pdf/0810.5262">pdf</a></p> http://www.vallis.org/blogspace/2008/10/29#0810.5336 <p class="story_para"> <b>Authors</b>: K.G. Arun, Alessandra Buonanno, Guillaume Faye, Evan Ochsner </p> <p class="story_para"> <b>Date</b>: 29 Oct 2008 </p> <p class="story_para"> <b>Abstract</b>: We provide ready-to-use time-domain gravitational waveforms for spinning compact binaries with precession effects through 1.5PN order in amplitude and compute their mode decomposition using spin-weighted -2 spherical harmonics. In the presence of precession, the gravitational-wave modes (l,m) contain harmonics originating from combinations of the orbital frequency and precession frequencies. We find that the gravitational radiation from binary systems with large mass asymmetry and large inclination angle can be distributed among several modes. For example, during the last stages of inspiral, for some maximally spinning configurations, the amplitude of the (2,0) and (2,1) modes can be comparable to the amplitude of the (2,2) mode. If the mass ratio is not too extreme, the l=3 and l=4 modes are generally one or two orders of magnitude smaller than the l = 2 modes. Restricting ourselves to spinning, non-precessing compact binaries, we apply the stationary-phase approximation and derive the frequency-domain gravitational waveforms including spin-orbit and spin(1)- spin(2) effects through 1.5PN and 2PN order respectively in amplitude, and 2.5PN order in phase. Since spin effects in the amplitude through 2PN order affect only the first and second harmonics of the orbital phase, they do not extend the mass reach of gravitational-wave detectors. However, they can interfere with other harmonics and lower or raise the signal-to-noise ratio depending on the spin orientation. These ready-to-use waveforms could be employed in the data-analysis of the spinning, inspiraling binaries as well as in comparison studies at the interface between analytical and numerical relativity. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0810.5336">abs</a> <a href="http://www.arxiv.org/pdf/0810.5336">pdf</a></p> http://www.vallis.org/blogspace/2008/10/29#0810.5255 <p class="story_para"> <b>Authors</b>: Christopher Eling, Jacob D. Bekenstein </p> <p class="story_para"> <b>Date</b>: 29 Oct 2008 </p> <p class="story_para"> <b>Abstract</b>: Hawking's area theorem guarantees the monotonic growth of the surface area of any black hole provided the matter and fields interacting with it respect the weak positive energy condition. The theorem does not identify specific effects which make it work in particular situations. We here report a specific gedanken experiment in which the theorem seems to be violated: the dropping of an electrically charged test object from rest at a point close to the horizon and on the symmetry axis of a nearly extreme Kerr black hole. In the parallel experiment involving a magnetically charged Reissner-Nordstrom hole, the analogous violation is defused by taking into account a subtle source of repulsion of the charge: the spinning up of the black hole in the process of bringing the charge down to its dropping point. No such effect is known for the Kerr case; we find the electric self-force of the charge to be insufficient to right matters. After exhaustive analysis of the problem we conclude that some, as yet unknown, classical effect must be responsible for the enforcement of the area theorem. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0810.5255">abs</a> <a href="http://www.arxiv.org/pdf/0810.5255">pdf</a></p> http://www.vallis.org/blogspace/2008/10/29#0810.4848 <p class="story_para"> <b>Authors</b>: C.H. Lenzi, M. Malheiro, R. M. Marinho, C. Provid&amp;#xea;ncia, G. F. Marranghello </p> <p class="story_para"> <b>Date</b>: 27 Oct 2008 </p> <p class="story_para"> <b>Abstract</b>: The direct detection of gravitational waves will provide valuable astrophysical information about many celestial objects. The most promising sources of gravitational waves are neutron stars and black holes. These objects emit waves in a very wide spectrum of frequencies determined by their quasi-normal modes oscillations. In this work we are concerned with the information we can extract from f and p$_I$-modes when a candidate leaves its signature in the resonant mass detectors ALLEGRO, EXPLORER, NAUTILUS, MiniGrail and SCHENBERG. Using the empirical equations, that relate the gravitational wave frequency and damping time with the mass and radii of the source, we have calculated the radii of the stars for a given interval of masses $M$ in the range of frequencies that include the bandwidth of all resonant mass detectors. With these values we obtain diagrams of mass-radii for different frequencies that allowed to determine the better candidates to future detection taking in account the compactness of the source. Finally, to determine which the models of compact stars emit gravitational waves in the frequency band of the mass resonant detectors, we compare the mass-radii diagrams obtained by different neutron stars sequences from several relativistic hadronic equations of state (GM1, GM3, TM1, NL3) and quark matter equations of state (NJL, MTI bag model). We verify that quark stars obtained from MIT bag model with bag constant equal to 170 MeV and quark of matter in color-superconductivity phase are the best candidates for mass resonant detectors. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/0810.4848">abs</a> <a href="http://www.arxiv.org/pdf/0810.4848">pdf</a></p>