Subject: ASGRG Newsletter #9
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AUSTRALASIAN SOCIETY FOR GENERAL RELATIVITY AND GRAVITATION
Electronic Newsletter -- #9, Autumn 2002
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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 30 September, 2002.
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CONTENTS:
* 2002 AIP CONGRESS, Sydney, 8-11 July, 2002
* DEATH OF GEOFFREY OPAT
* POSITION AT UNIVERSITY OF CANBERRA
* MEMBERSHIP DETAILS ONLINE at
http://www.physics.adelaide.edu.au/ASGRG/members.html
* SUBSCRIPTIONS
* FORTHCOMING MEETINGS
* MEMBERS' ABSTRACTS at gr-qc, December 2001 - April 2002
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2002 CONGRESS OF THE AUSTRALIAN INSTITUTE OF PHYSICS
The 15th Biennial Congress of the Australian Institute of Physics is
to be held at the Sydney Convention and Exhibition Centre, Darling
Harbour, Sydney from the 8th to the 11th of July 2002. The Plenary
Speaker for the ASGRG Interest Group will be Prof Barry Barish from
CalTech, Director of LIGO.
A total of 18 abstracts have been submitted to the AIP as part of the
ASGRG Interest Group's contribution, and we have inherited 2 further
talks from the collapse of the Astronomy Interest Group.
The latest draft version of the ASGRG timetable (as of April 25) reads:
Session 1, Monday 8 July, 1400-1530
Anderson: Self-similar evaporation of a rigidly rotating cosmic string
loop.
Scott: General properties of cosmological models with an isotropic
singularity.
Ericksson: A characterising feature of cosmological models with an
isotropic singularity.
Darabi: A gravitational conformal invariant model and coupling constants
in 5D non-compact Kaluza-Klein models.
Mititelu: Periodic solutions for the geodesic equations in the Reissner-
Nordstrom metric.
Session 2, Monday 8 July, 1700-1830
Ashley: The abstract boundary construction and singularity theorems.
Beesham: Gravitational collapse of higher dimensional inhomogeneous
dust.
Flambaum: Do the fundamental constants of Nature vary with time and
distance?
Murphy: A variable fine structure constant? New results.
Robinson: A variation of the spacetime geometry equation.
Session 3, Wednesday 10 July, 1700-1900 (Jointly with AOP)
Hanbury Brown retrospective.
De Vine: Experimental demonstration of a variable reflectivity signal
mirror for a Michelson interferometer GW detector.
Brooks: Wavefront distortion in optical cavities for gravitational
wave interferometers.
Session 4, Thursday 11 July, 1430-1615
Barish (Plenary): The status and prospects for LIGO.
McClelland: Progress report from ACIGA.
Scott: Gravitational wave astronomy strategies and AIGO.
Session 5, Thursday 11 July, 1645-1830
Cusack: Global correlations in physical environment monitors for
gravitational wave detection.
Searle: Spectral line removal for GW astronomy.
Tobar: Michelson-Morley experiment using whispering spherical mode
resonators.
Slagmolen: Direct measurement of the thermal noise of a flexure
suspension.
Hollitt: A direct measurement of the spectrum of thermoelastic
noise in sapphire.
Ju Li: Vibration isolation and test mass suspension for laser
interferometer gravitational wave detector.
A full list of the AIP abstracts can be found at:
http://www.aip.org.au/Congress2002/AbstractNew.htm
A reminder that the deadline for early registration at the AIP
Congress is the 16th of May 2002.
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DEATH OF GEOFFREY OPAT
It is with great sadness that we report the sudden death of Geoffrey
Opat on March 7 of this year. Geoff was a member of the School of
Physics at the University of Melbourne, and had been a member of the
ASGRG since 1996.
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POSITION AT UNIVERSITY OF CANBERRA
A researcher with expertise in mathematical aspects of the Einstein
equations is sought, to work on an ARC-supported project on "Energy in
General Relativity" at the University of Canberra. The position is for 18
months, and would suit a recent PhD graduate in mathematics or theoretical
physics with a background in geometry and analysis. Questions may be
directed to bartnik@ise.canberra.edu.au. Application details are available
at
http://www.canberra.edu.au/recruitment/jobs/job-02-2024.html
Please bring this notice to the attention of potential candidates. The
formal closing date was 12th April 2002, but late applications will be
considered.
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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.
However, this year subscription details were posted out on April 21,
for some unknown reason. This was definitely not initiated by ASGRG
staff, and was possibly triggered by a robot or a hacker exploring the
ASGRG website. In any case, all corrections mailed back to the asgrg
website should now have been made to the subscription database.
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 2002 - June 2003 subscriptions are requested, if you wish to
pay for July 2003 - June 2004 at the same time, it may simplify matters.
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FORTHCOMING MEETINGS
May 31-June 2, 2002: 5th Capra Ranch Meeting on Radiation Reaction
in General Relativity
State College, Pennsylvania, USA
http://cgwp.gravity.psu.edu/capra5
June 10-11, 2002: BritGravII
Queen Mary College, London, UK
http://www.maths.qmul.ac.uk/~britgrav/
June 18-29, 2002: Cosmoseismology and Entropy Perturbations
University of Portsmouth, Portsmouth, UK
http://www.gravity.port.ac.uk/cosmoseismology
June 22-July 3, 2002: XIV Petrov School: Recent Problems in Theoretical
and Mathematical Physics
Kazan, Tatarstan, Russia
http://www.kcn.ru/petrov_school/2let_e.htm
June 24-29, 2002: Numerical Relativity
University of Minnesota, USA
http://www.ima.umn.edu/nr/
June 26-29, 2002: 6th International Conference on the History of
General Relativity
Amsterdam, Netherlands
http://www.science.uva.nl/~kox/HGR6.html
July 1-5, 2002: XVIIIth IAP Colloquium: On the Nature of Dark Energy
Institut d'Astrophysique de Paris, France
http://www.iap.fr/Conferences/Colloque/col2002
July 1-8, 2002: GRG11: Theoretical and Experimental Problems of GR
Tomsk, Russia
July 8-11, 2002: 15th Biennial Congress of the Australian Institute of
Physics
Darling Harbour, Sydney, Australia
http://www.aip.org.au/Congress2002
July 12-15, 2002: XIth Oporto Meeting on Geometry, Topology and
Physics
Oporto, Portugal
http://www.fc.up.pt/mp/actividades/om.html
July 15-20, 2002: Black holes, Gravitational Waves and Cosmology
Rome/Pescara, Italy
http://www.icra.it/ICRA_Networkshops/INW10_RJR60/
July 15-30, 2002: Strings 2002
Cambridge, UK
http://www.damtp.cam.ac.uk/strings2002/
July 19-24, 2002: 4th International LISA Symposium
State College, Pennsylvania, USA
http://cgwp.phys.psu.edu
July 29-August 9, 2002: Xth Brazilian School of Cosmology and
Gravitation
Mangaratiba, Brazil
http://www.cosmologia.cbpf.br
July 29-August 10, 2002: 50 Years of the Cauchy Problem in General
Relativity
Cargese, Corsica, France
http://www.phys.univ-tours.fr/%7Epiotr/cargese/announcement
August 26-29, 2002: 12th Chinese Conference on Gravitation and
Relativistic Astrophysics
Yaan City, Sichuan Province, China
September 5-6, 2002: Applications of Geometric Algebra
Trinity College, Cambridge, UK
http://www.clifford.org/~clf-alg/conferences.html
September 6-10, 2002: 'Villa Mondragone' International School of
Gravitation and Cosmology
Villa Mondragone, Monte Porzio Catone (Rome), Italy
http://www.sigrav.unige.it
September 9-14, 2002: 2nd ISPM Workshop on Particles & Cosmology
Tbilisi, Georgia
http://www.rmi.acnet.ge/ispm
November 15-18, 2002: Brane World 2
Kyoto, Japan
November 26-29, 2002: 12th Japan GRG Workshop
Tokyo, Japan
December 9-13, 2002: XXIst Texas Symposium on Relativistic
Astrophysics
Florence, Italy
http://www.arcetri.astro.it/%7Etexaflor/
2003: 10th Marcel Grossmann Meeting on General Relativity
Rio de Janeiro, Brazil
http://www.icra.it/MG/mg10/Welcome.htm
Dec 2003/Jan 2004: 4th Conference of the ASGRG (ACGRG4)
Monash University, Melbourne, Australia
July 2004: 17th International Conference of the ISGRG (GR 17)
Dublin, Ireland
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MEMBERS' ABSTRACTS at gr-qc, December 2001 - April 2002
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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Paper: gr-qc/0203015
From: Reg Cahill
Date: Tue, 5 Mar 2002 04:41:44 GMT (48kb)
Process Physics: From Quantum Foam to General Relativity
Authors: Reginald T. Cahill
Comments: 26 pages Latex, 1 separate eps file
Progress in the new information-theoretic process physics is reported in
which the link to the phenomenology of general relativity is made. In
process physics the fundamental assumption is that reality is to be
modelled as self-organising semantic (or internal or relational)
information using a self-referentially limited neural network model.
Previous progress in process physics included the demonstration that
space and quantum physics are emergent and unified, with time a distinct
non-geometric process, that quantum phenomena are caused by fractal
topological defects embedded in and forming a growing three-dimensional
fractal process-space, which is essentially a quantum foam. Other features
of the emergent physics were: quantum field theory with emergent flavour
and confined colour, limited causality and the Born quantum measurement
metarule, inertia, time-dilation effects, gravity and the equivalence
principle, a growing universe with a cosmological constant, black holes
and event horizons, and the emergence of classicality. Here general
relativity and the technical language of general covariance is seen not to
be fundamental but a phenomenological construct, arising as an amalgam of
two distinct phenomena: the `gravitational' characteristics of the emergent
quantum foam for which `matter' acts as a sink, and the classical
`spacetime' measurement protocol, but with the later violated by quantum
measurement processes. Quantum gravity, as manifested in the emergent
Quantum Homotopic Field Theory of the process-space or quantum foam, is
logically prior to the emergence of the general relativity phenomenology,
and cannot be derived from it.
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Paper: hep-ph/0202168
From: Robert Brandenberger
Date: Sun, 17 Feb 2002 11:23:54 GMT (11kb)
Microwave Background Constraints on Decaying Defects
Authors: Robert H. Brandenberger, Brandon Carter, Anne-Christine Davis
Comments: 6 pages, 0 figures
Embedded defects are predicted in a host of particle physics theories, in
particular in the standard electroweak theory. They can be stabilized by
interactions with the cosmological plasma, but will decay once the plasma
falls out of equilibrium, emitting a substantial fraction of non-thermal
photons. If the decay happens after a redshift of about $10^6$, these
photons will give rise to spectral distortions of the Cosmic Microwave
Background, which leads to strong constraints on the underlying particle
physics theory. Such constraints apply to any model with decaying defects,
and in particular to theories predicting decaying vortons, thereby leading
to constraints stronger than the dark matter limit.
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Paper: hep-ph/0201155
From: Robert Brandenberger
Date (v1): Thu, 17 Jan 2002 14:40:12 GMT (31kb)
Date (revised v2): Sun, 17 Feb 2002 13:28:08 GMT (32kb)
Thermal Stabilisation of Superconducting Sigma Strings and their Drum
Vortons
Authors: Brandon Carter, Robert H. Brandenberger, Anne-Christine Davis
Comments: 16 pages, 2 figures two references added
We discuss various issues related to stabilized embedded strings in a
thermal background. In particular, we demonstrate that such strings will
generically become superconducting at moderately low temperatures, thus
enhancing their stability. We then present a new class of defects - drum
vortons - which arise when a small symmetry breaking term is added to the
potential. We display these points within the context of the O(4) sigma
model, relevant for hadrodynamics below the QCD scale. This model admits
`embedded defects' (topological defect configurations of a simpler - in
this case O(2) symmetric - model obtained by imposing an embedding
constraint) that are unstable in the full model at zero temperature, but
that can be stabilised (by electromagnetic coupling to photons) in a
thermal gas at moderately high termperatures. It is shown here that below
the embedded defect stabilisation threshold, there will still be stabilized
cosmic string defects. However, they will not be of the symmetric embedded
vortex type, but of an `asymmetric' vortex type, and are automatically
superconducting. In the presence of weak symmetry breaking terms, such as
arise naturally when using the O(4) model for hadrodynamics, the strings
become the boundary of a new kind of cosmic sigma membrane, with tension
given by the pion mass. The string current would then make it possible for
a loop to attain a (classically) stable equilibrium state that differs from
an ``ordinary'' vorton state by the presence of a sigma membrane stretched
across it in a drum like configuration. Such defects will however be
entirely destabilised if the symmetry breaking is too strong, as is found
to be the case -- due to the rather large value of the pion mass -- in the
hadronic application of the O(4) sigma model.
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Paper: gr-qc/0201002
From: Dr Simon Brian Davis
Date (v1): Mon, 31 Dec 2001 21:57:05 GMT (10kb)
Date (revised v2): Wed, 13 Feb 2002 17:41:21 GMT (11kb)
The quantum theory of a quadratic gravity action for heterotic strings
Authors: Simon Davis, Hugh Luckock
Comments: 12 pages. Renormalizability properties of the action are
clarified and a third-order differential equation for the wave function
$\Psi$ with a dependence on the potential $V(\Phi)$ is included
Report-no: University of Sydney Report 2001-17
The wave function for the quadratic gravity theory derived from the
heterotic string effective action is deduced to first order in
${{e^{-\Phi}}\over {g_4^2}}$ by solving a perturbed second-order
Wheeler-DeWitt equation, assuming that the potential is slowly varying
with respect to $\Phi$. Predictions for inflation based on the solution
to the second-order Wheeler-DeWitt equation continue to hold for this
theory. It is shown how formal expressions for the average paths in
minisuperspace $\{< a(t) >, < \Phi(t)> \}$ determine the shifts from
the classical solutions to $a_{cl}(t)$ and $\Phi_{cl}(t)$, which occur
only at third order in the expansion of the integrals representing the
expectation values.
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Paper: gr-qc/0112051
From: Hossein Farajollahi
Date (v1): Thu, 20 Dec 2001 06:10:37 GMT (15kb)
Date (revised v2): Fri, 21 Dec 2001 01:49:16 GMT (15kb)
Dirac observables and the phase space of general relativity
Authors: Hossein Farajollahi, Hugh Luckock
Comments: Latex,18 pages,no figures
In the canonical approach to general relativity it is customary to
parametrize the phase space by initial data on spacelike hypersurfaces.
However, if one seeks a theory dealing with observations that can be made
by a single localized observer, it is natural to use a different
description of the phase space. This results in a different set of Dirac
observables from that appearing in the conventional formulation. It also
suggests a possible solution to the problem of time, which has been one
of the obstacles to the development of a satisfactory quantum theory of
gravity.
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Paper: gr-qc/0203094
From: Marie-Noelle Celerier
Date: Tue, 26 Mar 2002 16:16:26 GMT (19kb)
Timelike and null focusing singularities in spherical symmetry: a solution
to the cosmological horizon problem and a challenge to the cosmic
censorship hypothesis
Authors: Marie-Noelle Celerier (Observatoire de Paris-Meudon), Peter
Szekeres (University of Adelaide)
Comments: 26 pages, 2 figures, LaTeX file. Submitted to Phys. Rev. D
Extending the study of spherically symmetric metrics satisfying the
dominant energy condition and exhibiting singularities of power-law type
initiated in SI93, we identify two classes of peculiar interest: focusing
timelike singularity solutions with the stress-energy tensor of a
radiative perfect fluid (equation of state: $p={1\over 3} \rho$) and a
set of null singularity classes verifying identical properties. We
consider two important applications of these results: to cosmology, as
regards the possibility of solving the horizon problem with no need to
resort to any inflationary scenario, and to the Strong Cosmic Censorship
Hypothesis to which we propose a class of physically consistent
counter-examples.
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Paper: gr-qc/0204062
From: visser@tui.wustl.edu (Matt Visser)
Date: Fri, 19 Apr 2002 02:33:15 GMT (19kb)
Sakharov's induced gravity: a modern perspective
Authors: Matt Visser (Washington University in Saint Louis)
Comments: mpla.sty; 17 pages. Contribution to the ``First IUCAA Meeting on
the Interface of Gravitational and Quantum Realms'', held in Pune in
December 2001.
To appear in Modern Physics Letters A
Sakharov's 1967 notion of ``induced gravity'' is currently enjoying a
significant resurgence. The basic idea, originally presented in a very
brief 3-page paper with a total of 4 formulas, is that gravity is not
``fundamental'' in the sense of particle physics. Instead it was argued
that gravity (general relativity) emerges from quantum field theory in
roughly the same sense that hydrodynamics or continuum elasticity theory
emerges from molecular physics. In this article I will translate the key
ideas into modern language, and explain the various versions of Sakharov's
idea currently on the market.
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Paper: gr-qc/0204022
From: visser@tui.wustl.edu (Matt Visser)
Date (v1): Fri, 5 Apr 2002 02:20:47 GMT (24kb)
Date (revised v2): Wed, 17 Apr 2002 19:49:54 GMT (24kb)
The quantum physics of chronology protection
Authors: Matt Visser (Washington University in Saint Louis)
Comments: CUP style: uses cmmp.cls; 18 pages; contribution to "The future
of theoretical physics and cosmology", conference in honour of Professor
Stephen Hawking on the occasion of his 60'th birthday.
V2: Some references added
This is a brief survey of the current status of Stephen Hawking's
``chronology protection conjecture''. That is: ``Why does nature abhor a
time machine?'' I'll discuss a few examples of spacetimes containing
``time machines'' (closed causal curves), the sorts of peculiarities that
arise, and the reactions of the physics community. While pointing out
other possibilities, this article concentrates on the possibility of
``chronology protection''. As Stephen puts it: ``It seems that there is a
Chronology Protection Agency which prevents the appearance of closed
timelike curves and so makes the universe safe for historians.''
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Paper: gr-qc/0204017
From: visser@tui.wustl.edu (Matt Visser)
Date: Thu, 4 Apr 2002 02:25:15 GMT (19kb)
Bi-refringence versus bi-metricity
Authors: Matt Visser (Washington University in Saint Louis), Carlos
Barcelo (Portsmouth University), Stefano Liberati (University of
Maryland)
Comments: Revtex 4; 10 pages in double-column format; contribution to the
Festschrift in honour of Professor Mario Novello
In this article we carefully distinguish the notion of bi-refringence (a
polarization-dependent doubling in photon propagation speeds) from that of
bi-metricity (where the two photon polarizations ``see'' two distinct
metrics). We emphasise that these notions are logically distinct, though
there are special symmetries in ordinary (3+1)-dimensional nonlinear
electrodynamics which imply the stronger condition of bi-metricity.
To illustrate this phenomenon we investigate a generalized version of
(3+1)-dimensional nonlinear electrodynamics, which permits the inclusion
of arbitrary inhomogeneities and background fields. [For example
dielectrics (a la Gordon), conductors (a la Casimir), and gravitational
fields (a la Landau--Lifshitz).] It is easy to demonstrate that the
generalized theory is bi-refringent: In (3+1) dimensions the Fresnel
equation, the relationship between frequency and wavenumber, is always
quartic. It is somewhat harder to show that in some cases (eg, ordinary
nonlinear electrodynamics) the quartic factorizes into two quadratics thus
providing a bi-metric theory. Sometimes the quartic is a perfect square,
implying a single unique effective metric. We investigate the generality
of this factorization process.
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Paper: gr-qc/0203061
From: Carlos O. Lousto
Date: Mon, 18 Mar 2002 22:02:14 GMT (12kb)
Reconstruction of Black Hole Metric Perturbations from Weyl Curvature
Authors: Carlos O. Lousto (UT Brownsville), Bernard F. Whiting (U Florida)
Comments: 6 Pages, Revtex4
Report-no: UTBRG-2001-03
Perturbation theory of rotating black holes is usually described in terms
of Weyl scalars $\psi_4$ and $\psi_0$, which each satisfy Teukolsky's
complex master wave equation and respectively represent outgoing and
ingoing radiation. On the other hand metric perturbations of a Kerr hole
can be described in terms of (Hertz-like) potentials $\Psi$ in outgoing or
ingoing {\it radiation gauges}. In this paper we relate these potentials
to what one actually computes in perturbation theory, i.e $\psi_4$ and
$\psi_0$. We explicitly construct these relations in the nonrotating limit,
preparatory to devising a corresponding approach for building up the
perturbed spacetime of a rotating black hole. We discuss the application
of our procedure to second order perturbation theory and to the study of
radiation reaction effects for a particle orbiting a massive black hole.
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Paper: gr-qc/0202086
From: Steven Detweiler
Date (v1): Mon, 25 Feb 2002 20:34:29 GMT (8kb)
Date (revised v2): Thu, 7 Mar 2002 21:13:44 GMT (9kb)
Self-force via a Green's function decomposition
Authors: Steven Detweiler, Bernard F. Whiting
Comments: 4 pages; new paragraph on gauge condition; corrected reference;
added acknowledgment; minor text changes
The gravitational field of a particle of small mass \mu moving through
curved spacetime is naturally decomposed into two parts each of which
satisfies the perturbed Einstein equations through O(\mu). One part is
an inhomogeneous field which, near the particle, looks like the \mu/r
field distorted by the local Riemann tensor; it does not depend on the
behavior of the source in either the infinite past or future. The other
part is a homogeneous field and includes the ``tail term''; it completely
determines the self force effects of the particle interacting with its own
gravitational field, including radiation reaction. Self force effects for
scalar, electromagnetic and gravitational fields are all described in this
manner.
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