Subject: ASGRG Newsletter #16
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AUSTRALASIAN SOCIETY FOR GENERAL RELATIVITY AND GRAVITATION
Electronic Newsletter -- #16, 2006
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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.
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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
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Texas in Australia:
23rd Texas Symposium on Relativistic Astrophysics
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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)
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18th International Conference
on General Relativity and Gravitation (GR18)
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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
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7th Edoardo Amaldi Conference
on Gravitational Waves
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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
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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.
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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.
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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
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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 $\Omega_{gw} > 2.2 \times 10^{-17}$.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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