Subject: ASGRG Newsletter #16 ****************************************************************************** AUSTRALASIAN SOCIETY FOR GENERAL RELATIVITY AND GRAVITATION Electronic Newsletter -- #16, 2006 ****************************************************************************** Items for this newsletter should be emailed to the editor: asgrg *AT* hotmail *DOT* com The deadline for the next issue is 31 October, 2007. ****************************************************************************** CONTENTS: * TEXAS IN AUSTRALIA: 23RD TEXAS SYMPOSIUM ON RELATIVISTIC ASTROPHYSICS * 18TH INTERNATIONAL CONFERENCE ON GENERAL RELATIVITY AND GRAVITATION (GR18) * 7TH EDOARDO AMALDI CONFERENCE ON GRAVITATIONAL WAVES * MEMBERSHIP DETAILS ONLINE at http://www.physics.adelaide.edu.au/ASGRG/members.html * SUBSCRIPTIONS * FORTHCOMING MEETINGS * MEMBERS' ABSTRACTS at gr-qc, December 2005 - November 2006 * ABSTRACTS FROM THE LIGO SCIENTIFIC COLLABORATION at gr-qc, December 2005 - November 2006 ****************************************************************************** Texas in Australia: 23rd Texas Symposium on Relativistic Astrophysics -------------------------------------------------------------------------- TEXAS IN AUSTRALIA: UNIVERSITY OF MELBOURNE, 11-15 DECEMBER 2006 www.texas06.com In keeping with the aims and spirit of previous Texas Symposia, the meeting will provide a forum for presenting the latest results in relativistic astrophysics: cosmology, gravitation, and high-energy astrophysical phenomena. We are delighted to host the 2006 Symposium and look forward to providing a program that provides memorable social as well as scientific experiences! The venue for the conference is the University of Melbourne, Parkville. The space is comfortable and fantastically located, close to all the amenities of Melbourne's CBD. Please join us in December 2006. Best regards, Andrew Melatos and Rachel Webster (chairs of the SOC) ****************************************************************************** 18th International Conference on General Relativity and Gravitation (GR18) -------------------------------------------------------------------------- GR18: DARLING HARBOUR, SYDNEY, 8-13 JULY 2007 www.grg18.com (Running in parallel with the 7th Edoardo Amaldi Conference on Gravitational Waves) Joining forces in Sydney in 2007 these conferences will bring together the world's leading scientists working in the fields of General Relativity and Gravitation. The program for GRG18 will incorporate all areas of General Relativity and Gravitation including Classical General Relativity; Relativistic Astrophysics and Cosmology; Experimental Work on Gravity and Quantum Issues in Gravitation. The Amaldi 7 program will cover all aspects of Gravitational Wave Physics and Detection. Sydney is situated on one of the world's most beautiful and famous harbours. Renowned for its iconic landmarks, the Sydney Opera House and Harbour Bridge, Sydney boasts many attractions including stunning beaches, fantastic shops and restaurants. The conference will be held at Darling Harbour located within walking distance of the heart of the city. It is one of Sydney's most exciting tourist precincts offering waterfront restaurants and cafes, beautiful gardens and a range of exciting attractions. To find out more about GRG18 or Amaldi7, please register your interest now at www.grg18.com or www.amaldi7.com ****************************************************************************** 7th Edoardo Amaldi Conference on Gravitational Waves -------------------------------------------------------------------------- AMALDI7: DARLING HARBOUR, SYDNEY, 8-14 JULY 2007 www.amaldi7.com The Amaldi conferences are held under the auspices of the Gravitational Wave International Committee (GWIC). Since 1999, they have been held every two years and are regarded as the most important international conferences for the gravitational wave detection community. The 2007 conference promises to be an extremely exciting meeting for the field. The LIGO detectors will have completed a one and half year data taking run in coincidence with GEO600, TAMA 300 and VIRGO at various times during the run. This will produce the greatest chance yet of the first direct observation of gravitational waves, a momentous event in physics. Direct detection will open a new field in Astronomy. Exciting plans for second generation detectors and beyond will guarantee a rich return. Major advances in acoustic detectors will see their future assured, complementing the interferometric detectors in various frequency ranges, whilst research on space based detectors is gathering momentum. New theoretical results in fields such as numerical relativity will add greatly to our understanding of such phenomena as the inspiral of black holes. The Conference Social Program has been specifically designed to allow delegates time away from the formalities of the conference sessions to network and exchange ideas with colleagues and friends from around the world. Sydney is an ideal location, situated on one of the worlds most beautiful and famous harbours Renowned for its iconic landmarks, the Sydney Opera House and Harbour Bridge, delegate’s and their partners will be have the opportunity to experience a unique social and tour program showcasing the highlights of Sydney. I look forward to welcoming you to Sydney in 2007. Dr. Massimo Cerdonio Chair Gravitational Wave International Committee SOC, Edoardo Amaldi Conferences on Gravitational Waves ****************************************************************************** MEMBERSHIP DETAILS ONLINE: Due to requests from members, David Wiltshire has written some HTML scripts which generate membership details online from our records. If you click on http://www.physics.adelaide.edu.au/ASGRG/members.html you will find a members' list. Clicking on individual members gives their current contact details. By following a further link private details of the subscription status of any member will be sent to their registered email. This feature should enable us to update our records more frequently in response to members' input, and to allow members to keep track of their subscriptions. ****************************************************************************** SUBSCRIPTIONS: The membership script programs are intended to be run automatically once a year, at the end of July, to give members other than life members details of their current subscription status. The new version of the subscription form, at http://www2.phys.canterbury.ac.nz/ASGRG/subsform.html has been simplified so that it does not need to be updated each year. Given that our annual fee is modest, members are encouraged to pay for multiple years, and to fill in the years they are paying for. E.g., when the July 2007 - June 2008 subscriptions are requested, if you wish to pay for July 2008 - June 2009 at the same time, it may simplify matters. ****************************************************************************** FORTHCOMING MEETINGS December 11-15, 2006: Texas in Australia: 23rd Texas Symposium on Relativistic Astrophysics University of Melbourne, Melbourne, Australia http://www.texas06.com December 18-21, 2006: 11th Gravitational Wave Data Analysis Workshop Dorint Novotel, Potsdam, Germany http://gwdaw11.aei.mpg.de January 29 - February 2, 2007: TIARA Winter School - Astrophysical Black Holes National Tsing Hua University, Taiwan https://www.tiara.sinica.edu.tw/activities/winterschool/2007/main.html April 3-4, 2007: 7th British Gravitational Conference (Britgrav7) Centre for Mathematical Sciences, Cambridge, UK http://www.srcf.ucam.org/~ea212/Britgrav7 April 10-13, 2007: Bilbao Encounter on New Standard Cosmology University of the Basque Country, Bilbao, Spain http://www.ehu.es/bicos/ May 10-12, 2007: Dynamics and Thermodynamics of Black Holes and Naked Singularities Politecnico di Milano, Milan, Italy http://www.mate.polimi.it/bh2/ July 8-13, 2007: 18th International Conference on General Relativity and Gravitation (GR18) Darling Harbour, Sydney, Australia http://www.grg18.com July 8-14, 2007: 7th Edoardo Amaldi Conference on Gravitational Waves Darling Harbour, Sydney, Australia http://www.amaldi7.com ****************************************************************************** MEMBERS' ABSTRACTS at gr-qc, December 2005 - November 2006 We list here all new abstracts that we are aware of that have been submitted by our members to gr-qc, or which are cross-linked at gr-qc. (We have not searched for abstracts on other Los Alamos archives which are not crosslinked to gr-qc.) If you do not send your papers to gr-qc but would like to have them noted in the newsletters, please send them to the Editor. ----------------------------------------------------------------------------- gr-qc/0512091 From: Robert Bartnik Date: Thu, 15 Dec 2005 14:04:27 GMT (20kb) Spherically symmetric dynamical horizons Authors: Robert Bartnik, Jim Isenberg Comments: latex, 19 pages, no figures Report-no: NI05079 Journal-ref: Class.Quant.Grav. 23 (2006) 2559-2570 We determine sufficient and necessary conditions for a spherically symmetric initial data set to satisfy the dynamical horizon conditions in the spacetime development. The constraint equations reduce to a single second order linear master equation, which leads to a systematic construction of all spherically symmetric dynamical horizons (SSDH) satisfying certain boundedness conditions. We also find necessary and sufficient conditions for a given spherically symmetric spacetime to contain a SSDH. ----------------------------------------------------------------------------- gr-qc/0512097 From: Robert Bartnik Date: Fri, 16 Dec 2005 09:58:28 GMT (4kb) A note on static metrics Authors: Robert Bartnik, Paul Tod Comments: latex, 4 pages, no figures Report-no: NI05080 Journal-ref: Class.Quant.Grav. 23 (2006) 569-572 Conditions are given which, subject to a genericity condition on the Ricci tensor, are both necessary and sufficient for a 3-metric to arise from a static spacetime metric. ----------------------------------------------------------------------------- gr-qc/0605134 From: Dr. Bikash Chandra Paul Date: Fri, 26 May 2006 12:05:03 GMT (7kb) Emergent Universe with Exotic Matter Authors: S. Mukherjee, B. C. Paul, N. K. Dadhich, S. D. Maharaj, A. Beesham Comments: 11 pages, no fig Journal-ref: Class.Quant.Grav. 23 (2006) 6927-6934 A general framework for an emergent universe scenario has been given which makes use of an equation of state. The general features of the model have also been studied and possible primordial composition of the universe have been suggested. ----------------------------------------------------------------------------- gr-qc/0602096 From: Chunnong Zhao Date (v1): Fri, 24 Feb 2006 06:59:43 GMT (121kb) Date (revised v2): Tue, 28 Feb 2006 07:35:55 GMT (121kb) Compensation of Strong Thermal Lensing in High Optical Power Cavities Authors: C. Zhao, J. Degallaix, L. Ju, Y. Fan, D.G. Blair, B.J.J. Slagmolen, M.B. Gray, C.M. Mow Lowry, D.E. McClellandl, D. J. Hosken, D. Mudge, A. Brooks, J. Munch, P.J. Veitch, M. A. Barton, G. Billingsley Comments: 8 pages Journal-ref: Phys.Rev.Lett. 96 (2006) 231101 In an experiment to simulate the conditions in high optical power advanced gravitational wave detectors such as Advanced LIGO, we show that strong thermal lenses form in accordance with predictions and that they can be compensated using an intra-cavity compensation plate heated on its cylindrical surface. We show that high finesse ~1400 can be achieved in cavities with internal compensation plates, and that the cavity mode structure can be maintained by thermal compensation. It is also shown that the measurements allow a direct measurement of substrate optical absorption in the test mass and the compensation plate. ----------------------------------------------------------------------------- gr-qc/0606003 From: Paul Lasky Date: Thu, 1 Jun 2006 01:32:36 GMT (57kb) Initial value formalism for dust collapse Authors: Paul Lasky, Anthony Lun, Raymond Burston (Monash University) Comments: 11 pages, 5 figures, Submitted to Phys. Rev. D (28/02/06) Formulating a dust filled spherically symmetric metric utilizing the 3+1 formalism for general relativity, we show that the metric coefficients are completely determined by the matter distribution, and it's time rate of change on an initial slice. Rather than specifying Schwarzschild coordinates for the exterior of the collapsing region, we let the interior dictate the form of the solution in the exterior, and thus both regions are found to be written in one coordinate patch. This not only alleviates the need for complicated matching schemes at the interface, but also finds a new coordinate system for the Schwarzschild spacetime expressed in generalized Painleve-Gullstrand coordinates. We show the interior metric is equivalent to the class of Tolman-Bondi metrics under a coordinate transformation. In particular, specifying the initial density as a step function the solution reduces to the Oppenheimer-Snyder model. In general, the solution is the class of Tolman-Bondi models, which are known to develop shell crossing singularities. We show these are equivalent to fluid shock waves and suggest methods for extending beyond their initial point of formation. ----------------------------------------------------------------------------- gr-qc/0610062 From: Raymond Burston Date: Thu, 12 Oct 2006 00:37:24 GMT (27kb) Electromagnetic perturbations of non-vacuum locally rotationally symmetric class II spacetimes Authors: Raymond Burston, Anthony Lun Comments: 15 pages, submitted to Classical and Quantum Gravity We present a method that yields three decoupled covariant equations for three complex scalars, which completely govern electromagnetic perturbations of non-vacuum, locally rotationally symmetric class II spacetimes. One of these equations is equivalent to the previously established generalized Regge-Wheeler equation for electromagnetic fields. The remaining two equations are a direct generalization of the Bardeen-Press equations. The approach undertaken makes use of the well established 3+1 (and 2+1+1) formalism, and therefore, it is an ideal setting for specifying interpretable energy-momentum on an initial spacelike three-slice as the perturbation sources to the resultant electromagnetic radiation. ----------------------------------------------------------------------------- gr-qc/0611052 From: Raymond Burston Date: Wed, 8 Nov 2006 11:58:22 GMT (28kb) Covariant Schwarzschild perturbations I: Initial value formulation for scalars of spin-weight -+ 2 Authors: R. B. Burston, A. W. C. Lun Comments: 17 pages. Submitted to Class. Quantum Grav We consider full perturbations to a covariantly defined Schwarzschild spacetime. By constructing complex quantities, we derive two decoupled, covariant and gauge-invariant, wave-like equations for spin-weighted scalars. These arise naturally from the Bianchi identities and comprise a covariant representation of the Bardeen-Press equations for scalars with spin-weight $\pm2$. Furthermore, the covariant and gauge-invariant 1+1+2 formalism is employed, and consequently, the physical interpretation of the energy-momentum perturbations is transparent. They are written explicitly in terms of the energy-momentum specified on spacelike three-slices. Ultimately, a Cauchy problem is constructed whereby, an initial three-slice may be perturbed by an energy-momentum source, which induces resultant gravitational fields. ----------------------------------------------------------------------------- gr-qc/0512024 From: Benedict Carter Date: Mon, 5 Dec 2005 04:21:47 GMT (6kb) Series solutions for a static scalar potential in a Salam-Sezgin Supergravitational hybrid braneworld Authors: Benedict M.N. Carter, Alex B. Nielsen Comments: 5 pages, no figures Journal-ref: Gen.Rel.Grav. 37 (2005) 1629-1634 The static potential for a massless scalar field shares the essential features of the scalar gravitational mode in a tensorial perturbation analysis about the background solution. Using the fluxbrane construction of [8] we calculate the lowest order of the static potential of a massless scalar field on a thin brane using series solutions to the scalar field's Klein Gordon equation and we find that it has the same form as Newton's Law of Gravity. We claim our method will in general provide a quick and useful check that one may use to see if their model will recover Newton's Law to lowest order on the brane. ----------------------------------------------------------------------------- hep-th/0512262 From: Ishwaree Neupane Date (v1): Wed, 21 Dec 2005 20:48:00 GMT (863kb) Date (revised v2): Wed, 24 May 2006 07:12:38 GMT (981kb) Towards inflation and dark energy cosmologies from modified Gauss-Bonnet theory Authors: Ishwaree P Neupane, Benedict M N Carter Comments: 35 pages, 21 eps figs; section 6 expanded improving explanations, refs added, final in JCAP Journal-ref: JCAP 0606 (2006) 004 DOI: 10.1088/1475-7516/2006/06/004 We consider a physically viable cosmological model that has a field dependent Gauss-Bonnet coupling in its effective action, in addition to a standard scalar field potential. The presence of such terms in the four dimensional effective action gives rise to several novel effects, such as a four dimensional flat Friedmann-Robertson-Walker universe undergoing a cosmic inflation at early epoch, as well as a cosmic acceleration at late times. The model predicts, during inflation, spectra of both density perturbations and gravitational waves that may fall well within the experimental bounds. Furthermore, this model provides a mechanism for reheating of the early universe, which is similar to a model with some friction terms added to the equation of motion of the scalar field, which can imitate energy transfer from the scalar field to matter. ----------------------------------------------------------------------------- hep-th/0602086 From: David Wiltshire Date (v1): Thu, 9 Feb 2006 19:25:36 GMT (102kb) Date (revised v2): Fri, 17 Feb 2006 04:08:29 GMT (102kb) Date (revised v3): Thu, 20 Jul 2006 21:39:06 GMT (104kb) Hybrid brane worlds in the Salam-Sezgin model Authors: Benedict M.N. Carter, Alex B. Nielsen, David L. Wiltshire Comments: 27 pages, 2 figures, JHEP3.cls; v3 small additional sub-section consistent with published version Journal-ref: JHEP 0607 (2006) 034 DOI: 10.1088/1126-6708/2006/07/034 We construct a 6-dimensional warped brane world compactification of the Salam-Sezgin supergravity model by generalizing an earlier hybrid Kaluza-Klein / Randall-Sundrum construction [hep-th/0109099]. In this construction the observed universe is interpreted as a 4-brane in six dimensions, with a Kaluza-Klein spatial direction in addition to the usual three noncompact spatial dimensions. This construction is distinct from other brane world constructions in six dimensions, which introduce the universe as a 3-brane corresponding to a topological defect in six dimensions, or which require a particular configuration of matter fields on the brane. We demonstrate that the model reproduces localized gravity on the brane in the expected form of a Newtonian potential with Yukawa-type corrections. We show that allowed parameter ranges include values which potentially solve the hierarchy problem. An exact nonlinear gravitational wave solution on the background is exhibited. The class of solutions given applies to Ricci-flat geometries in four dimensions, and consequently includes brane world realizations of the Schwarzschild and Kerr black holes as particular examples. Arguments are given which suggest that the hybrid compactification of the Salam-Sezgin model can be extended to reductions to arbitrary Einstein space geometries in four dimensions. ----------------------------------------------------------------------------- gr-qc/0604064 From: Brandon Carter Date: Sat, 15 Apr 2006 10:34:56 GMT (630kb) Half century of black-hole theory: from physicists' purgatory to mathematicians' paradise Authors: Brandon Carter Comments: 30 pages latex. Contrib. to Encuentros Relativistas Espanoles: A Century of Relativity Theory, Oviedo, 2005 (ed. L. Mornas) 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. ----------------------------------------------------------------------------- gr-qc/0605024 From: Lars Samuelsson Date (v1): Wed, 3 May 2006 22:31:49 GMT (25kb) Date (revised v2): Sat, 19 Aug 2006 16:30:26 GMT (26kb) Relativistic mechanics of neutron superfluid in (magneto) elastic star crust Authors: Brandon Carter, Lars Samuelsson Comments: 29 pages, Latex. V. 2. Minor changes, matches published version Journal-ref: Class.Quant.Grav. 23 (2006) 5367-5388 At densities below the neutron drip threshold, a purely elastic solid model (including, if necessary, a frozen-in magnetic field) can provide an adequate description of a neutron star crust, but at higher densities it will be necessary to allow for the penetration of the solid lattice by an independently moving current of superfluid neutrons. In order to do this, the previously available category of relativistic elasticity models is combined here with a separately developed category of relativistic superfluidity models in a unified treatment based on the use of an appropriate Lagrangian master function. As well as models of the purely variational kind, in which the vortices flow freely with the fluid, such a master function also provides a corresponding category of non-dissipative models in which the vortices are pinned to the solid structure. ----------------------------------------------------------------------------- gr-qc/0606117 From: Brandon Carter Date: Tue, 27 Jun 2006 15:02:28 GMT (7kb) Anthropic principle in cosmology Authors: Brandon Carter Comments: 6 pages, latex: contribution to Colloquium ``Cosmology: Facts and problems'', Paris, 2004 A brief explanation of the meaning of the anthropic principle - as a prescription for the attribution of a priori probability weighting - is illustrated by various cosmological and local applications, in which the relevant conclusions are contrasted with those that could be obtained from (less plausible) alternative prescriptions such as the vaguer and less restrictive ubiquity principle, or the more sterile and restrictive autocentric principle. ----------------------------------------------------------------------------- gr-qc/0604017 From: Hannes Helgason Date: Wed, 5 Apr 2006 01:25:22 GMT (128kb) Detecting Highly Oscillatory Signals by Chirplet Path Pursuit Authors: Emmanuel J. Candes, Philip R. Charlton, Hannes Helgason Subj-class: General Relativity and Quantum Cosmology; Statistics 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. ----------------------------------------------------------------------------- gr-qc/0512039 From: Neil J. Cornish Date: Tue, 6 Dec 2005 18:41:06 GMT (53kb) Detecting the Cosmic Gravitational Wave Background with the Big Bang Observer Authors: Vincent Corbin, Neil J. Cornish Comments: 15 pages, 12 Figures Journal-ref: Class.Quant.Grav. 23 (2006) 2435-2446 The detection of the Cosmic Microwave Background Radiation (CMB) was one of the most important cosmological discoveries of the last century. With the development of interferometric gravitational wave detectors, we may be in a position to detect the gravitational equivalent of the CMB in this century. The Cosmic Gravitational Background (CGB) is likely to be isotropic and stochastic, making it difficult to distinguish from instrument noise. The contribution from the CGB can be isolated by cross-correlating the signals from two or more independent detectors. Here we extend previous studies that considered the cross-correlation of two Michelson channels by calculating the optimal signal to noise ratio that can be achieved by combining the full set of interferometry variables that are available with a six link triangular interferometer. In contrast to the two channel case, we find that the relative orientation of a pair of coplanar detectors does not affect the signal to noise ratio. We apply our results to the detector design described in the Big Bang Observer (BBO) mission concept study and find that BBO could detect a background with $\Omega_{gw} > 2.2 \times 10^{-17}$. ----------------------------------------------------------------------------- gr-qc/0601036 From: Neil J. Cornish Date (v1): Tue, 10 Jan 2006 19:06:46 GMT (223kb) Date (revised v2): Tue, 17 Jan 2006 23:20:17 GMT (221kb) Darwin Meets Einstein: LISA Data Analysis Using Genetic Algorithms Authors: Jeff Crowder, Neil J. Cornish, Lucas Reddinger Comments: 8 pages, 12 figures Journal-ref: Phys.Rev. D73 (2006) 063011 This work presents the first application of the method of Genetic Algorithms (GAs) to data analysis for the Laser Interferometer Space Antenna (LISA). In the low frequency regime of the LISA band there are expected to be tens of thousands galactic binary systems that will be emitting gravitational waves detectable by LISA. The challenge of parameter extraction of such a large number of sources in the LISA data stream requires a search method that can efficiently explore the large parameter spaces involved. As signals of many of these sources will overlap, a global search method is desired. GAs represent such a global search method for parameter extraction of multiple overlapping sources in the LISA data stream. We find that GAs are able to correctly extract source parameters for overlapping sources. Several optimizations of a basic GA are presented with results derived from applications of the GA searches to simulated LISA data. ----------------------------------------------------------------------------- astro-ph/0604616 From: Neil J. Cornish Date: Fri, 28 Apr 2006 18:19:11 GMT (618kb) Extending the WMAP Bound on the Size of the Universe Authors: Joey Shapiro Key, Neil J. Cornish, David N. Spergel, Glenn D. Starkman Comments: 9 pages, 16 figures Clues to the shape of our Universe can be found by searching the CMB for matching circles of temperature patterns. A full sky search of the CMB, mapped extremely accurately by NASA's WMAP satellite, returned no detection of such matching circles and placed a lower bound on the size of the Universe at 24 Gpc. This lower bound can be extended by optimally filtering the WMAP power spectrum. More stringent bounds can be placed on specific candidate topologies by using a a combination statistic. We use optimal filtering and the combination statistic to rule out the infamous "soccer ball universe'' model. ----------------------------------------------------------------------------- gr-qc/0605085 From: Neil J. Cornish Date (v1): Mon, 15 May 2006 03:22:28 GMT (156kb) Date (revised v2): Wed, 9 Aug 2006 18:10:03 GMT (199kb) MCMC Exploration of Supermassive Black Hole Binary Inspirals Authors: Neil J. Cornish, Edward K. Porter Comments: Submitted to CQG as a GWDAW-10 Conference Proceedings, 9 pages, 5 figures, Published Version Journal-ref: Class.Quant.Grav. 23 (2006) S761-S768 The Laser Interferometer Space Antenna will be able to detect the inspiral and merger of Super Massive Black Hole Binaries (SMBHBs) anywhere in the Universe. Standard matched filtering techniques can be used to detect and characterize these systems. Markov Chain Monte Carlo (MCMC) methods are ideally suited to this and other LISA data analysis problems as they are able to efficiently handle models with large dimensions. Here we compare the posterior parameter distributions derived by an MCMC algorithm with the distributions predicted by the Fisher information matrix. We find excellent agreement for the extrinsic parameters, while the Fisher matrix slightly overestimates errors in the intrinsic parameters. ----------------------------------------------------------------------------- gr-qc/0605135 From: Neil J. Cornish Date (v1): Fri, 26 May 2006 19:56:30 GMT (256kb) Date (revised v2): Wed, 9 Aug 2006 18:01:07 GMT (151kb) Catching Super Massive Black Hole Binaries Without a Net Authors: Neil J. Cornish, Edward K. Porter Comments: 4 pages, 3 figures, Refined search algorithm, added low SNR example The gravitational wave signals from coalescing Supermassive Black Hole Binaries are prime targets for the Laser Interferometer Space Antenna (LISA). With optimal data processing techniques, the LISA observatory should be able to detect black hole mergers anywhere in the Universe. The challenge is to find ways to dig the signals out of a combination of instrument noise and the large foreground from stellar mass binaries in our own galaxy. The standard procedure of matched filtering against a grid of templates can be computationally prohibitive, especially when the black holes are spinning or the mass ratio is large. Here we develop an alternative approach based on Metropolis-Hastings sampling and simulated annealing that is orders of magnitude cheaper than a grid search. We demonstrate our approach on simulated LISA data streams that contain the signals from binary systems of Schwarzschild Black Holes, embedded in instrument noise and a foreground containing 26 million galactic binaries. The search algorithm is able to accurately recover the 9 parameters that describe the black hole binary without first having to remove any of the bright foreground sources, even when the black hole system has low signal-to-noise. ----------------------------------------------------------------------------- gr-qc/0608112 From: Louis Rubbo Date: Fri, 25 Aug 2006 17:15:39 GMT (798kb) Slice & Dice: Identifying and Removing Bright Galactic Binaries from LISA Data Authors: Louis J. Rubbo, Neil J. Cornish, Ronald W. Hellings Comments: 5 pages, 4 figures, proceedings paper for the Sixth International LISA Symposium Here we describe a hierarchal and iterative data analysis algorithm used for searching, characterizing, and removing bright, monochromatic binaries from the Laser Interferometer Space Antenna (LISA) data streams. The algorithm uses the F-statistic to provide an initial solution for individual bright sources, followed by an iterative least squares fitting for all the bright sources. Using the above algorithm, referred to as Slice & Dice, we demonstrate the removal of multiple, correlated galactic binaries from simulated LISA data. Initial results indicate that Slice & Dice may be a useful tool for analyzing the forthcoming LISA data. ----------------------------------------------------------------------------- gr-qc/0609105 From: Alberto Vecchio Date: Mon, 25 Sep 2006 17:45:50 GMT (7kb) The Mock LISA Data Challenges: An overview Authors: K. A. Arnaud, S. Babak, J. G. Baker, M. J. Benacquista, N. J. Cornish, C. Cutler, S. L. Larson, B. S. Sathyaprakash, M. Vallisneri, A. Vecchio, J-Y. Vinet (The Mock LISA Data Challenge Task Force) Comments: 6 pages, in Proceedings of the Sixth International LISA Symposium (AIP, 2006) The LISA International Science Team Working Group on Data Analysis (LIST-WG1B) is sponsoring several rounds of mock data challenges, with the purposeof fostering the development of LISA data analysis capabilities, and of demonstrating technical readiness for the maximum science exploitation of the LISA data. The first round of challenge data sets were released at the Sixth LISA Symposium. We briefly describe the objectives, structure, and time-line of this programme. ----------------------------------------------------------------------------- gr-qc/0609106 From: Alberto Vecchio Date: Mon, 25 Sep 2006 17:37:20 GMT (238kb) A How-To for the Mock LISA Data Challenges Authors: K. A. Arnaud, S. Babak, J. G. Baker, M. J. Benacquista, N. J. Cornish, C. Cutler, S. L. Larson, B. S. Sathyaprakash, M. Vallisneri, A. Vecchio, J-Y. Vinet (The Mock LISA Data Challenge Task Force) Comments: 10 pages, 1 figure, in Proceedings of the Sixth International LISA Symposium (AIP, 2006) The LISA International Science Team Working Group on Data Analysis (LIST-WG1B) is sponsoring several rounds of mock data challenges, with the purpose of fostering development of LISA data-analysis capabilities, and of demonstrating technical readiness for the maximum science exploitation of the LISA data. The first round of challenge data sets were released at this Symposium. We describe the models and conventions (for LISA and for gravitational-wave sources) used to prepare the data sets, the file format used to encode them, and the tools and resources available to support challenge participants. ----------------------------------------------------------------------------- astro-ph/0611546 From: Neil J. Cornish Date: Fri, 17 Nov 2006 06:25:12 GMT (162kb) A Solution to the Galactic Foreground Problem for LISA Authors: Jeff Crowder, Neil Cornish Comments: 19 pages, 27 figures Low frequency gravitational wave detectors, such as the Laser Interferometer Space Antenna (LISA), will have to contend with large foregrounds produced by millions of compact galactic binaries in our galaxy. While these galactic signals are interesting in their own right, the unresolved component can obscure other sources. The science yield for the LISA mission can be improved if the brighter and more isolated foreground sources can be identified and regressed from the data. Since the signals overlap with one another we are faced with a ``cocktail party'' problem of picking out individual conversations in a crowded room. Here we present and implement an end-to-end solution to the galactic foreground problem that is able to resolve tens of thousands of sources from across the LISA band. Our algorithm employs a variant of the Markov Chain Monte Carlo (MCMC) method, which we call the Blocked Annealed Metropolis-Hastings (BAM) algorithm. Following a description of the algorithm and its implementation, we give several examples ranging from searches for a single source to searches for hundreds of overlapping sources. Our examples include data sets from the first round of Mock LISA Data Challenges. ----------------------------------------------------------------------------- physics/0608124 From: Michael Edmund Tobar Date (v1): Fri, 11 Aug 2006 08:18:33 GMT (213kb) Date (revised v2): Wed, 4 Oct 2006 03:56:21 GMT (656kb) Cryogenic sapphire oscillator with exceptionally high long-term frequency stability Authors: J.G. Hartnett, C.R. Locke, E.N. Ivanov, M.E. Tobar, P.L. Stanwix Comments: Accepted for publication in Applied Physics Letters Subj-class: Instrumentation and Detectors; Classical Physics We report on the development of a sapphire cryogenic microwave resonator oscillator long-term fractional frequency stability of 2x10^-17Sqrt[\tau] for integration times \tau>10^3 s and negative drift of about 2.2x10^-15/day. The short-term frequency instability of the oscillator is highly reproducible and also state-of-the-art: 5.6x10^-16 for an integration time of \tau ~ 20 s. ----------------------------------------------------------------------------- physics/0608202 From: Michael Edmund Tobar Date: Sat, 19 Aug 2006 08:54:02 GMT (595kb) Long Term Operation and Performance of Cryogenic Sapphire Oscillators Authors: M.E. Tobar, E.N. Ivanov, C.R. Locke, P.L. Stanwix, J.G. Hartnett, A.N. Luiten, R.B. Warrington, P.T.H. Fisk, M.A. Lawn, M.J. Wouters, S. Bize, G. Santarelli, P. Wolf, A. Clairon, P. Guillemot Comments: Accepted for publication in IEEE Trans. UFFC 21st June 2006 Subj-class: Instrumentation and Detectors Cryogenic Sapphire Oscillators (CSO) developed at UWA have now been in operation around the world continuously for many years. Such oscillators, due to their excellent spectral purity are essential for interrogating atomic frequency standards at the limit of quantum projection noise; otherwise aliasing effects will dominate the frequency stability due to the periodic sampling between successive interrogations of the atomic transition. For this reason, UWA oscillators are now operational at NMI (Sydney), LNE-SYRTE (Paris), the French Space Agency (CNES, Toulouse) and at UWA (Perth). Other applications, which have attracted attention in recent years, include tests on fundamental principles of physics, such as tests of Lorentz invariance. This paper reports on the long-term operation and performance of such oscillators. We compare the long-term drift of some different CSOs. The drift rates turn out to be linear over many years and in the same direction. However, the magnitude seems to vary by more than one order of magnitude between the oscillators, ranging from 10^14 per day to a few parts in 10^13 per day. ----------------------------------------------------------------------------- gr-qc/0609072 From: Michael Edmund Tobar Date (v1): Tue, 19 Sep 2006 16:15:46 GMT (158kb) Date (revised v2): Tue, 3 Oct 2006 05:42:25 GMT (158kb) Improved test of Lorentz Invariance in Electrodynamics using Rotating Cryogenic Sapphire Oscillators Authors: Paul L. Stanwix, Michael E. Tobar, Peter Wolf, Clayton R. Locke, Eugene N. Ivanov Comments: Accepted for publication in Phys. Rev. D Subj-class: General Relativity and Quantum Cosmology; Instrumentation and Detectors Journal-ref: Phys.Rev. D74 (2006) 081101 We present new results from our test of Lorentz invariance, which compares two orthogonal cryogenic sapphire microwave oscillators rotating in the lab. We have now acquired over 1 year of data, allowing us to avoid the short data set approximation (less than 1 year) that assumes no cancelation occurs between the $\tilde{\kappa}_{e-}$ and $\tilde{\kappa}_{o+}$ parameters from the photon sector of the standard model extension. Thus, we are able to place independent limits on all eight $\tilde{\kappa}_{e-}$ and $\tilde{\kappa}_{o+}$ parameters. Our results represents up to a factor of 10 improvement over previous non rotating measurements (which independently constrained 7 parameters), and is a slight improvement (except for $\tilde{\kappa}_{e-}^{ZZ}$) over results from previous rotating experiments that assumed the short data set approximation. Also, an analysis in the Robertson-Mansouri-Sexl framework allows us to place a new limit on the isotropy parameter $P_{MM}=\delta-\beta+{1/2}$ of $9.4(8.1)\times10^{-11}$, an improvement of a factor of 2. ----------------------------------------------------------------------------- gr-qc/0606055 From: Paul Lasky Date (v1): Tue, 13 Jun 2006 00:01:14 GMT (15kb) Date (revised v2): Thu, 21 Sep 2006 05:58:48 GMT (16kb) Generalized Lemaitre-Tolman-Bondi Solutions with Pressure Authors: Paul Lasky, Anthony Lun Comments: Accepted for publication by Physical Reviews D Journal-ref: Phys.Rev. D74 (2006) 084013 DOI: 10.1103/PhysRevD.74.084013 Utilizing the ADM equations, we derive a metric and reduced field equations describing a general, spherically symmetric perfect fluid. The metric describes both the interior perfect fluid region and exterior vacuum Schwarzschild spacetime in a single coordinate patch. The exterior spacetime is in generalized Painleve-Gullstrand coordinates which is an infinite class of coordinate systems. In the static limit the system reduces to a Tolman-Oppenheimer-Volkoff equation on the interior with the exterior in Schwarzschild coordinates. We show the coordinate transformation for the non-static cases to comoving coordinates, where the metric is seen to be a direct generalization of the Lemaitre-Tolman-Bondi spacetime to include pressures. ----------------------------------------------------------------------------- gr-qc/0611002 From: Paul Lasky Date: Tue, 31 Oct 2006 22:36:43 GMT (18kb) Spherically Symmetric Gravitational Collapse of Perfect Fluids Authors: P. D. Lasky, A. W. C. Lun Comments: 3 pages, To appear in the proceedings of the eleventh Marcel Grossmann meeting on general relativity (MGXI), 23-29 July, 2006, Berlin Formulating a perfect fluid filled spherically symmetric metric utilizing the 3+1 formalism for general relativity, we show that the metric coefficients are completely determined by the mass-energy distribution, and its time rate of change on an initial spacelike hypersurface. Rather than specifying Schwarzschild coordinates for the exterior of the collapsing region, we let the interior dictate the form of the solution in the exterior, and thus both regions are found to be written in one coordinate patch. This not only alleviates the need for complicated matching schemes at the interface, but also finds a new coordinate system for the Schwarzschild spacetime expressed in generalized Painleve-Gullstrand coordinates. ----------------------------------------------------------------------------- gr-qc/0605002 From: Patrick Sutton Date (v1): Sat, 29 Apr 2006 03:54:04 GMT (915kb) Date (revised v2): Mon, 1 May 2006 21:08:52 GMT (917kb) Coherent network analysis technique for discriminating gravitational-wave bursts from instrumental noise Authors: Shourov Chatterji, Albert Lazzarini, Leo Stein, Patrick Sutton, Antony Searle, Massimo Tinto Comments: 18 pages, 11 figures; corrected corrupted figure Report-no: LIGO-P060009-01-E Journal-ref: Phys.Rev. D74 (2006) 082005 Existing coherent network analysis techniques for detecting gravitational-wave bursts simultaneously test data from multiple observatories for consistency with the expected properties of the signals. These techniques assume the output of the detector network to be the sum of a stationary Gaussian noise process and a gravitational-wave signal, and they may fail in the presence of transient non-stationarities, which are common in real detectors. In order to address this problem we introduce a consistency test that is robust against noise non-stationarities and allows one to distinguish between gravitational-wave bursts and noise transients. This technique does not require any a priori knowledge of the putative burst waveform. ----------------------------------------------------------------------------- gr-qc/0512127 From: Silke Weinfurtner Date: Thu, 22 Dec 2005 04:13:32 GMT (30kb) Modelling Planck-scale Lorentz violation via analogue models Authors: Silke Weinfurtner, Stefano Liberati, Matt Visser Comments: Talk given at the Fourth Meeting on Constrained Dynamics and Quantum Gravity (QG05), Cala Gonone (Sardinia, Italy) September 12-16, 2005 Journal-ref: J.Phys.Conf.Ser. 33 (2006) 373-385 Astrophysical tests of Planck-suppressed Lorentz violations had been extensively studied in recent years and very stringent constraints have been obtained within the framework of effective field theory. There are however still some unresolved theoretical issues, in particular regarding the so called "naturalness problem" - which arises when postulating that Planck-suppressed Lorentz violations arise only from operators with mass dimension greater than four in the Lagrangian. In the work presented here we shall try to address this problem by looking at a condensed-matter analogue of the Lorentz violations considered in quantum gravity phenomenology. Specifically, we investigate the class of two-component BECs subject to laser-induced transitions between the two components, and we show that this model is an example for Lorentz invariance violation due to ultraviolet physics. We shall show that such a model can be considered to be an explicit example high-energy Lorentz violations where the ''naturalness problem'' does not arise. ----------------------------------------------------------------------------- gr-qc/0512139 From: Matt Visser Date (v1): Thu, 22 Dec 2005 21:36:59 GMT (11kb) Date (revised v2): Fri, 17 Mar 2006 00:07:39 GMT (11kb) Naturalness in emergent spacetime Authors: Stefano Liberati (SISSA/ISAS and INFN, Trieste), Matt Visser (Victoria University of Wellington, New Zealand), Silke Weinfurtner (Victoria University of Wellington, New Zealand) Comments: V1:4 pages, revtex4; V2: slight changes in title, presentation, and conclusions. This version to appear in Physical Review Letters Journal-ref: Phys.Rev.Lett. 96 (2006) 151301 Effective field theories (EFTs) have been widely used as a framework in order to place constraints on the Planck suppressed Lorentz violations predicted by various models of quantum gravity. There are however technical problems in the EFT framework when it comes to ensuring that small Lorentz violations remain small -- this is the essence of the "naturalness" problem. Herein we present an "emergent" space-time model, based on the "analogue gravity'' programme, by investigating a specific condensed-matter system that is in principle capable of simulating the salient features of an EFT framework with Lorentz violations. Specifically, we consider the class of two-component BECs subject to laser-induced transitions between the components, and we show that this model is an example for Lorentz invariance violation due to ultraviolet physics. Furthermore our model explicitly avoids the "naturalness problem", and makes specific suggestions regarding how to construct a physically reasonable quantum gravity phenomenology. ----------------------------------------------------------------------------- astro-ph/0512213 From: Tristan Faber Date (v1): Thu, 8 Dec 2005 02:06:23 GMT (26kb) Date (revised v2): Tue, 18 Jul 2006 22:40:44 GMT (83kb) Combining rotation curves and gravitational lensing: How to measure the equation of state of dark matter in the galactic halo Authors: Tristan Faber, Matt Visser (Victoria University of Wellington, New Zealand) Comments: V1: 6 pages, no figures, uses mn2e.cls. V2: 8 pages; 1 figure; uses mn2e.cls. Added sections 6 and 7, some minor changes and references. This version to appear in Monthly Notices of the Royal Astronomical Society Journal-ref: Mon.Not.Roy.Astron.Soc. 372 (2006) 136-142 DOI: 10.1111/j.1365-2966.2006.10845.x We argue that combined observations of galaxy rotation curves and gravitational lensing not only allow the deduction of a galaxy's mass profile, but also yield information about the pressure in the galactic fluid. We quantify this statement by enhancing the standard formalism for rotation curve and lensing measurements to a first post-Newtonian approximation. This enhanced formalism is compatible with currently employed and established data analysis techniques, and can in principle be used to reinterpret existing data in a more general context. The resulting density and pressure profiles from this new approach can be used to constrain the equation of state of the galactic fluid, and therefore might shed new light on the persistent question of the nature of dark matter. ----------------------------------------------------------------------------- gr-qc/0604058 From: Carlos Barcelo Date: Wed, 12 Apr 2006 11:21:58 GMT (162kb) Quasi-particle creation by analogue black holes Authors: Carlos Barcelo, Stefano Liberati, Sebastiano Sonego, Matt Visser Comments: 30 pages, 16 figures Journal-ref: Class.Quant.Grav. 23 (2006) 5341-5366 We discuss the issue of quasi-particle production by ''analogue black holes'' with particular attention to the possibility of reproducing Hawking radiation in a laboratory. By constructing simple geometric acoustic models, we obtain a somewhat unexpected result: We show that in order to obtain a stationary and Planckian emission of quasi-particles, it is not necessary to create an ergoregion in the acoustic spacetime (corresponding to a supersonic regime in the flow). It is sufficient to set up a dynamically changing flow either eventually generating an arbitrarily small sonic region v=c, but without any ergoregion, or even just asymptotically, in laboratory time, approaching a sonic regime with sufficient rapidity. ----------------------------------------------------------------------------- gr-qc/0605121 From: Silke Weinfurtner Date: Mon, 22 May 2006 11:28:16 GMT (72kb) Analogue spacetime based on 2-component Bose-Einstein condensates Authors: Silke Weinfurtner, Stefano Liberati, Matt Visser Comments: Chapter contributed to "Quantum Simulations via Analogues: From Phase Transitions to Black Holes", based on the COSLAB Dresden workshop, July 2005, to appear in the Springer "Lecture Notes in Physics" (LNP) series Analogue spacetimes are powerful models for probing the fundamental physical aspects of geometry - while one is most typically interested in ultimately reproducing the pseudo-Riemannian geometries of interest in general relativity and cosmology, analogue models can also provide useful physical probes of more general geometries such as pseudo-Finsler spacetimes. In this chapter we shall see how a 2-component Bose-Einstein condensate can be used to model a specific class of pseudo-Finsler geometries, and after suitable tuning of parameters, both bi-metric pseudo-Riemannian geometries and standard single metric pseudo-Riemannian geometries, while independently allowing the quasi-particle excitations to exhibit a "mass". Furthermore, when extrapolated to extremely high energy the quasi-particles eventually leave the phononic regime and begin to act like free bosons. Thus this analogue spacetime exhibits an analogue of the "Lorentz violation" that is now commonly believed to occur at or near the Planck scale defined by the interplay between quantum physics and gravitational physics. In the 2-component Bose-Einstein analogue spacetime we will show that the mass generating mechanism for the quasi-particles is related to the size of the Lorentz violations. This relates the "mass hierarchy" to the so-called "naturalness problem". In short the analogue spacetime based on 2-component Bose-Einstein condensates exhibits a very rich mathematical and physical structure that can be used to investigate many issues of interest to the high-energy physics, cosmology, and general relativity communities. ----------------------------------------------------------------------------- gr-qc/0607001 From: Matt Visser Date: Sat, 1 Jul 2006 05:42:53 GMT (9kb) Solution generating theorems for the TOV equation Authors: Petarpa Boonserm (Victoria University of Wellington), Matt Visser (Victoria University of Wellington), Silke Weinfurtner (Victoria University of Wellington) Comments: 11 pages; uses iopart.sty The Tolman-Oppenheimer-Volkov [TOV] equation constrains the internal structure of general relativistic static perfect fluid spheres. We develop several "solution generating" theorems for the TOV, whereby any given solution can be "deformed" to a new solution. Because the theorems we develop work directly in terms of the physical observables -- pressure profile and density profile -- it is relatively easy to check the density and pressure profiles for physical reasonableness. This work complements our previous article [Phys. Rev. D71 (2005) 124307; gr-qc/0503007] wherein a similar "algorithmic" analysis of the general relativistic static perfect fluid sphere was presented in terms of the spacetime geometry -- in the present analysis the pressure and density are primary and the spacetime geometry is secondary. In particular, our "deformed" solutions to the TOV equation are conveniently parameterized in terms of delta rho_c and delta p_c, the shift in the central density and central pressure. ----------------------------------------------------------------------------- gr-qc/0607008 From: Carlos Barcelo Date: Mon, 3 Jul 2006 12:00:50 GMT (17kb) Hawking-like radiation does not require a trapped region Authors: Carlos Barcelo, Stefano Liberati, Sebastiano Sonego, Matt Visser Comments: revtex4, 4 pages, 1 figure We discuss the issue of quasi-particle production by ''analogue black holes'' with particular attention to the possibility of reproducing Hawking radiation in a laboratory. By constructing simple geometric acoustic models, we obtain a somewhat unexpected result: We show that in order to obtain a stationary and Planckian emission of quasi-particles, it is not necessary to create a trapped region in the acoustic spacetime (corresponding to a supersonic regime in the fluid flow). It is sufficient to set up a dynamically changing flow asymptotically approaching a sonic regime with sufficient rapidity in laboratory time. ----------------------------------------------------------------------------- gr-qc/0609064 From: Celine Cattoen Date: Mon, 18 Sep 2006 03:31:01 GMT (19kb) Cosmological milestones and energy conditions Authors: Celine Cattoen, Matt Visser Comments: 8 pages, 1 table, conference proceedings for NEB XII conference in Nafplio, Greece Until recently, the physically relevant singularities occurring in FRW cosmologies had traditionally been thought to be limited to the "big bang", and possibly a "big crunch". However, over the last few years, the zoo of cosmological singularities considered in the literature has become considerably more extensive, with "big rips" and "sudden singularities" added to the mix, as well as renewed interest in non-singular cosmological events such as "bounces" and "turnarounds". In this talk, we present an extensive catalogue of such cosmological milestones, both at the kinematical and dynamical level. First, using generalized power series, purely kinematical definitions of these cosmological events are provided in terms of the behaviour of the scale factor a(t). The notion of a "scale-factor singularity" is defined, and its relation to curvature singularities (polynomial and differential) is explored. Second, dynamical information is extracted by using the Friedmann equations (without assuming even the existence of any equation of state) to place constraints on whether or not the classical energy conditions are satisfied at the cosmological milestones. Since the classification is extremely general, and modulo certain technical assumptions complete, the corresponding results are to a high degree model-independent. ----------------------------------------------------------------------------- gr-qc/0609073 From: Celine Cattoen Date: Wed, 20 Sep 2006 00:20:18 GMT (14kb) Generalized Puisieux series expansion for cosmological milestones Authors: Celine Cattoen (Victoria University of Wellington), Matt Visser (Victoria University of Wellington) Comments: 3 pages, using World Scientific templates, conference proceedings for MG11 Berlin, July 2006, to be published by World Scientific We use generalized Puisieux series expansions to determine the behaviour of the scale factor in the vicinity of typical cosmological milestones occurring in a FRW universe. We describe some of the consequences of this generalized Puisieux series expansion on other physical observables. ----------------------------------------------------------------------------- gr-qc/0609088 From: Petarpa Boonserm Date: Wed, 20 Sep 2006 23:43:49 GMT (20kb) Solution generating theorems for perfect fluid spheres Authors: Petarpa Boonserm (Victoria University of Wellington), Matt Visser (Victoria University of Wellington), Silke Weinfurtner (Victoria University of Wellington) Comments: 8 pages, no figures, to appear in the proceedings of the NEB XII Conference (Recent Developments in Gravity), 29 June - 2 July, 2006, Napflio, Greece The first static spherically symmetric perfect fluid solution with constant density was found by Schwarzschild in 1918. Generically, perfect fluid spheres are interesting because they are first approximations to any attempt at building a realistic model for a general relativistic star. Over the past 90 years a confusing tangle of specific perfect fluid spheres has been discovered, with most of these examples seemingly independent from each other. To bring some order to this collection, we develop several new transformation theorems that map perfect fluid spheres into perfect fluid spheres. These transformation theorems sometimes lead to unexpected connections between previously known perfect fluid spheres, sometimes lead to new previously unknown perfect fluid spheres, and in general can be used to develop a systematic way of classifying the set of all perfect fluid spheres. In addition, we develop new ``solution generating'' theorems for the TOV, whereby any given solution can be ``deformed'' to a new solution. Because these TOV-based theorems work directly in terms of the pressure profile and density profile it is relatively easy to impose regularity conditions at the centre of the fluid sphere. ----------------------------------------------------------------------------- gr-qc/0609099 From: Petarpa Boonserm Date: Fri, 22 Sep 2006 02:51:21 GMT (28kb) Solution generating theorems: perfect fluid spheres and the TOV equation Authors: Petarpa Boonserm (Victoria University of Wellington), Matt Visser (Victoria University of Wellington), Silke Weinfurtner (Victoria University of Wellington) Comments: 3 pages, 0 figures, to appear in the proceedings of the Eleventh Marcel Grossmann Meeting on General Relativity (MG11), 23 - 29 July, 2006, Berlin, Germany We report several new transformation theorems that map perfect fluid spheres into perfect fluid spheres. In addition, we report new ''solution generating'' theorems for the TOV, whereby any given solution can be ''deformed'' to a new solution. ----------------------------------------------------------------------------- gr-qc/0611070 From: Larry Price Date: Mon, 13 Nov 2006 20:24:50 GMT (20kb) On the Existence of Radiation Gauges in Petrov type II spacetimes Authors: Larry R. Price, Karthik Shankar, Bernard F. Whiting Comments: 21 pages, uses iop style files, submitted to CQG The radiation gauges used by Chrzanowski (his IRG/ORG) for metric reconstruction in the Kerr spacetime seem to be over-specified. Their specification consists of five conditions: four (which we treat here as) ''gauge'' conditions plus an additional condition on the trace of the metric perturbation. In this work, we utilize a newly developed form of the perturbed Einstein equations to establish a condition -- on a particular tetrad component of the stress-energy tensor -- under which one can impose the full IRG/ORG. In a Petrov type II background, imposing the IRG/ORG additionally requires (consistently) setting a particular component of the metric perturbation to zero ``by hand''. By contrast, in a generic type D background, gauge freedom can generally be used to achieve this. As a specific example, we work through the process of imposing the IRG in a Schwarzschild background, using a more traditional approach. Implications for metric reconstruction using the Teukolsky curvature perturbations in type D spacetimes are briefly discussed. ****************************************************************************** ABSTRACTS FROM THE LIGO SCIENTIFIC COLLABORATION at gr-qc, December 2005 - November 2006 The LIGO Scientific Collaboration is a consortium of scientific institutions doing work on the Laser Interferometer Gravitational-Wave Observatory (LIGO), which consists of two laser interferometers 3030 km apart, one at Hanford, Washington State and the other at Livingston, Louisiana. The LIGO Scientific Collaboration includes ASGRG members David McClelland, Susan Scott and Antony Searle, who are all at the Australian National University. ----------------------------------------------------------------------------- gr-qc/0512078 From: Stephen Fairhurst Date (v1): Tue, 13 Dec 2005 16:26:56 GMT (103kb) Date (revised v2): Fri, 6 Oct 2006 18:44:09 GMT (105kb) Joint LIGO and TAMA300 Search for Gravitational Waves from Inspiralling Neutron Star Binaries Authors: LIGO Scientific Collaboration, TAMA Collaboration Comments: 9 pages, 5 figures. Updated with published version Report-no: LIGO-P050017-01-Z Journal-ref: Phys.Rev. D73 (2006) 102002 We search for coincident gravitational wave signals from inspiralling neutron star binaries using LIGO and TAMA300 data taken during early 2003. Using a simple trigger exchange method, we perform an inter- collaboration coincidence search during times when TAMA300 and only one of the LIGO sites were operational. We find no evidence of any gravitational wave signals. We place an observational upper limit on the rate of binary neutron star coalescence with component masses between 1 and 3 M_sun of 49 per year per Milky Way equivalent galaxy at a 90% confidence level. The methods developed during this search will find application in future network inspiral analyses. ----------------------------------------------------------------------------- gr-qc/0605028 From: M. Alessandra Papa Date (v1): Thu, 4 May 2006 22:41:39 GMT (302kb) Date (revised v2): Wed, 31 May 2006 22:37:31 GMT (302kb) Coherent searches for periodic gravitational waves from unknown isolated sources and Scorpius X-1: results from the second LIGO science run Authors: The LIGO Scientific Collaboration Comments: 35 pages, 30 figures Report-no: LIGO-P050008-03 We carry out two searches for periodic gravitational waves using the most sensitive few hours of data from the second LIGO science run. The first search is targeted at isolated, previously unknown neutron stars and covers the entire sky in the frequency band 160-728.8 Hz. The second search targets the accreting neutron star in the low-mass X-ray binary Scorpius X-1, covers the frequency bands 464-484 Hz and 604-624 Hz, and two binary orbit parameters. Both searches look for coincidences between the Livingston and Hanford 4-km interferometers. For isolated neutron stars our 95% confidence upper limits on the gravitational wave strain amplitude range from 6.6E-23 to 1E-21 across the frequency band; For Scorpius X-1 they range from 1.7E-22 to 1.3E-21 across the two 20-Hz frequency bands. The upper limits presented in this paper are the first broad-band wide parameter space upper limits on periodic gravitational waves using coherent search techniques. The methods developed here lay the foundations for upcoming hierarchical searches of more sensitive data which may detect astrophysical signals. ----------------------------------------------------------------------------- astro-ph/0608606 From: Vuk Mandic Date (v1): Mon, 28 Aug 2006 21:18:15 GMT (617kb) Date (revised v2): Thu, 21 Sep 2006 22:36:40 GMT (616kb) Searching for a Stochastic Background of Gravitational Waves with LIGO Authors: LIGO Scientific Collaboration Comments: 37 pages, 16 figures The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed the fourth science run, S4, with significantly improved interferometer sensitivities with respect to previous runs. Using data acquired during this science run, we place a limit on the amplitude of a stochastic background of gravitational waves. For a frequency independent spectrum, the new limit is $\Omega_{\rm GW} < 6.5 \times 10^{-5}$. This is currently the most sensitive result in the frequency range 51-150 Hz, with a factor of 13 improvement over the previous LIGO result. We discuss complementarity of the new result with other constraints on a stochastic background of gravitational waves, and we investigate implications of the new result for different models of this background. -----------------------------------------------------------------------------