# Electronic Newsletter -- #7 Autumn 2001

Items for this newsletter should be emailed to the editor: asgrg *AT* hotmail *DOT* com

CONTENTS:

## ACGRG3, PERTH, 11-13 July, 2001 - CALL FOR PAPERS EXTENDED

The most important event on our calendar this year is ACGRG3. For full details see

Previously, there was a deadline of February 28 for the submission of titles and abstracts of talks. However, the response to this has been somewhat disappointing. The deadline is therefore being extended to April 30. Please get those titles and abstracts in.

## BIENNIEL GENERAL MEETING, Perth, 11 July, 2001

The business meeting of the Society will be held in Perth in conjunction with ACGRG3. Nominations - with name of nominee, nominator and seconder for any of the positions on the committee should be secretary at asgrg *AT* hotmail *DOT* com by 10 July, 2001.

## MEMBERSHIP DETAILS ONLINE

Due to requests from members, the secretary has written some HTML scripts which generate membership details online from our records. If you click on

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

We would like to apologise for being slow about sending out subscription notices. (The secretary was on sabbatical last year, and is now due to make an international move in a few months time.) Subscription notices had not been sent til now, even though the current financial year ends on 30 June, 2001.

To avoid problems in future the new version of the membership script programs will be run automatically once a year to give members other than life members details of their current subscription status. Initially the program will be run after this newsletter is sent, and then at the end of July each year.

The new version of the subscription form

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., now that July 2000 - June 2001 subscriptions are finally being requested, if you wish to pay for July 2001 - June 2002 at the same time, it may simplify matters.

## BID FOR GR17

Susan Scott is currently putting together a bid by the Society to hold the international General Relativity conference GR17 - next in the series after this year's meeting in Durban - in Cairns in July, 2004, at the new Cairns Convention Centre.

The conferences are traditionally held in the northern hemisphere summer, and thus a Queensland location is the ideal one. As it is a large event most of the organization would be done by professionals.

The bid must be presented at this year's GR16 conference in Durban, and will be on our agenda for discussion at the BGM in Perth. However, given the short timeframe between ACGRG3 and GR16 the following week, if there are any points wish members wish to raise in relation to the bid, they should contact Susan now directly.

## REPORT ON ASGRG WORKSHOP IN CONJUNCTION WITH AIP'2000

### Adelaide, 10-15 December 2000 (Copy of item to appear in "the Physicist")

The workshop consisted of two afternoons of talks, one experimental and one theoretical. In the experimental session Dr David McClelland gave a fascinating overview of the present worldwide effort to detect gravitational waves with the network of laser interferometer observatories. He explained why he believed that gravitational waves would be detected within the next 10 years, discussed the technical challenges involved, and gave a glimpse on the new field of gravitational wave astronomy which will emerge once the technology becomes a reality. In the remaining talks we were presented with more detailed discussions of particular experimental projects, as well as the immense effort in data reduction which will be required.

The theoretical sessions were wide ranging, covering all aspects of gravitational physics, from mathematical relativity to cosmology and to string theory. Dr Peter Bouwknegt presented an overview of recent results in string theory, while Dr David Wiltshire presented an overview of the now popular "brane world" scenario, in which extra spatial dimensions are either compact but larger than had been previously considered to be the case, or possibly infinite. The more technical talks covered topics including the evidence for a vacuum energy in the universe - "quintessence" - and possible models to explain it, cosmic strings, solutions of Einstein's equations on null characteristics, and mathematical properties of abstract boundaries and singularities, both in Einstein's theory and generalizations which include fields from string theory.

Though small, the meeting was a great success, and we look forward in July, 2001 to both the "4th Edoardo Amaldi Conference on Gravitational Waves" in Perth http://www.gravity.uwa.edu.au/amaldi/amaldi.htm and the "Third Australasian Conference on General Relativity and Gravitation" http://www2.phys.canterbury.ac.nz/ASGRG/ACGRG3/ which is being held this time as a satellite meeting to the international Amaldi conference.

## MEMBERS' NEWS

• Congratulations to Robert Bartnik, Malcolm Gray, David McClelland and Peter Veitch on their respective ARC large grant successes.

• David Wiltshire will be taking up a continuing lectureship at the Dept of Physics and Astronomy, University of Canterbury, Christchurch, NZ from July, 2001.

## MEMBERS' ABSTRACTS AT gr-qc January - July, 2000

We list here all 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/0009023
From: Reg Cahill
Date: Fri, 8 Sep 2000 03:47:32 GMT   (134kb)

Title: Process Physics: Modelling Reality as Self-Organising Information
Authors: Reginald T. Cahill, Christopher M. Klinger and Kirsty Kitto
\\
The new Process Physics models reality as self-organising relational
information and takes account of the limitations of logic, discovered by Godel
and extended by Chaitin, by using the concept of self-referential noise. Space
and quantum physics are emergent and unified, and described by a Quantum
Homotopic Field Theory of fractal topological defects embedded in a three
dimensional fractal process-space.
\\ ( http://au.arXiv.org/abs/gr-qc/0009023 ,  134kb)
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Paper: gr-qc/0101028
Date: Mon, 8 Jan 2001 20:29:46 GMT   (50kb)

Title: A brief review of Regge calculus in classical numerical relativity
Authors: Adrian P. Gentle and Warner A. Miller
Comments: 2 pages, submitted to the Proceedings of the IX Marcel Grossmann
Meeting, Rome, July 2-8, 2000
Report-no: LAUR-00-5816
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We briefly review past applications of Regge calculus in classical numerical
relativity, and then outline a programme for the future development of the
field. We briefly describe the success of lattice gravity in constructing
initial data for the head-on collision of equal mass black holes, and discuss
recent results on the efficacy of Regge calculus in the continuum limit.
\\ ( http://au.arXiv.org/abs/gr-qc/0101028 ,  50kb)
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Paper: astro-ph/0010443
From: David Wiltshire
Date: Mon, 23 Oct 2000 12:24:15 GMT (36kb)

Title: Supernovae Ia, evolution and quintessence
Authors: D.L. Wiltshire
Comments: 5 pages, 2 figures, aipproc, epsfig. To appear in "Cosmology and
Particle Physics", Proceedings of the CAPP'2000 Conference, Verbier, eds. J.
Garcia-Bellido, R. Durrer and M. Shaposhnikov, (AIP, 2001)

Quintessence models with a dark energy generated by pseudo Nambu-Goldstone
bosons provide a natural framework in which to test the possibility that type
Ia supernovae luminosity distance measurements are at least partially due to an
evolution of the sources, since these models can have parameter values for
which the expansion of the Universe is decelerating as well as values for which
it is accelerating, while being spatially flat in all cases and allowing for a
low density of clumped matter. The results of a recent investigation
(astro-ph/0004138) of current observational bounds which allow for SNe Ia
source evolution are discussed. It is found that models with source evolution
still favour cosmologies with an appreciable amount of acceleration in the
recent past, but that the region of parameter space which is most favoured
shifts significantly.

\\ ( http://au.arXiv.org/abs/astro-ph/00010443 , 36kb)
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Paper: gr-qc/0011023
From: Alan Barnes
Date: Tue, 7 Nov 2000 13:06:50 GMT (6kb)

Title: On Cyclically Symmetrical Spacetimes
Authors: Alan Barnes (Aston University Birmingham)
Comments: 6 pages, LaTex. (World Scientific style file: sprocl.sty needed) To
appear in Proceedings of the Spanish Relativity Meeting (EREs2000), World
Scientific Publishing

In a recent paper Carot et al. considered the definition of cylindrical
symmetry as a specialisation of the case of axial symmetry. One of their
propositions states that if there is a second Killing vector, which together
with the one generating the axial symmetry, forms the basis of a
two-dimensional Lie algebra, then the two Killing vectors must commute, thus
generating an Abelian group. In this paper a similar result, valid under
considerably weaker assumptions, is derived: any two-dimensional Lie
transformation group which contains a one-dimensional subgroup whose orbits are
circles, must be Abelian. The method used to prove this result is extended to
apply three-dimensional Lie transformation groups. It is shown that the
existence of a one-dimensional subgroup with closed orbits restricts the
Bianchi type of the associated Lie algebra to be I, II, III, VII_0, VIII or IX.
Some results on n-dimensional Lie groups are also derived and applied to show
there are severe restrictions on the structure of the allowed four-dimensional
Lie transformation groups compatible with cyclic symmetry.

\\ ( http://au.arXiv.org/abs/gr-qc/0011023 , 6kb )
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Paper: gr-qc/0011054
From: Leo Brewin
Date: Wed, 15 Nov 2000 14:12:02 GMT (25kb)

Title: Stable evolution of a maximally sliced Schwarzschild spacetime using a
smooth lattice
Authors: Leo Brewin
Comments: 3 pages, 4 eps figures, talk given at MG9, Rome, July 2000

We will present results of a long term stable evolution, to $t=1000m$, of a
maximally sliced Schwarzschild blackhole using a smooth lattice method.

\\ ( http://au.arXiv.org/abs/gr-qc/0011054 , 25kb )
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Paper: gr-qc/0012036
From: Brandon CARTER
Date (v1): Sun, 10 Dec 2000 10:18:00 GMT (33kb)
Date (revised v2): Mon, 29 Jan 2001 16:06:24 GMT (33kb)

Title: Essentials of Classical Brane Dynamics
Authors: Brandon Carter
Comments: 37 pages, Latex, revised to update references. Based on talk on 5
June, 2000 at Meudon Colloquium Motivations for and Implications of Extra
Cosmological Dimensions'' (transparencies visible on line at this http URL)
Contribution to proc. Peyresq 5 meeting, June 2000, Quantum spacetime,
Brane Cosmology, and Stochastic Effective Theories''

This article provides a self contained overview of the geometry and dynamics of
relativistic brane models, of the category that includes point particle,
string, and membrane representations for phenomena that can be considered as
being confined to a worldsheet of the corresponding dimension (respectively
one, two, and three) in a thin limit approximation in an ordinary 4 dimensional
spacetime background. This category also includes brane world'' models that
treat the observed universe as a 3-brane in 5 or higher dimensional background.
The first sections are concerned with purely kinematic aspects: it is shown
how, to second differential order, the geometry (and in particular the inner
and outer curvature) of a brane worldsheet of arbitrary dimension is
describable in terms of the first, second, and third fundamental tensor. The
later sections show how -- to lowest order in the thin limit -- the evolution
of such a brane worldsheet will always be governed by a simple tensorial
equation of motion whose left hand side is the contraction of the relevant
surface stress tensor $bar T^{\mu\nu}$ with the (geometrically defined) second
fundamental tensor $K_{\mu\nu}{^\rho}$, while the right hand side will simply
vanish in the case of free motion and will otherwise be just the orthogonal
projection of any external force density that may happen to act on the brane.

\\ ( http://au.arXiv.org/abs/gr-qc/0012036 , 33kb )
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Paper: gr-qc/0012047
From: Tevian Dray
Date: Wed, 13 Dec 2000 21:53:33 GMT (5kb)

Title: Note on Signature Change and Colombeau Theory
Authors: Tevian Dray, George Ellis, Charles Hellaby
Comments: REVTex, 3 pages; to appear in GRG

Recent work alludes to various controversies' associated with signature change
in general relativity. As we have argued previously, these are in fact
disagreements about the (often unstated) assumptions underlying various
possible approaches. The choice between approaches remains open.

\\ ( http://au.arXiv.org/abs/gr-qc/0012047 , 5kb )
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Paper: gr-qc/0101010
From: Brandon CARTER
Date (v1): Mon, 1 Jan 2001 07:40:03 GMT (16kb)
Date (revised v2): Mon, 29 Jan 2001 14:39:43 GMT (16kb)

Title: Reflection symmetry breaking scenarios with minimal gauge form coupling
in brane world cosmology
Authors: Brandon Carter, Jean-Philippe Uzan
Comments: 13 pages latex (revised to rectify a couple of sign transcription
errors)

consequences of dropping the usual Z_2 reflection symmetry postulate in brane
world scenarios. It is observed that for a cosmological model of homogeneous
isotropic type, the relevant generalised Birkhoff theorem establishing
staticity of the external vacuum in the maximally symmetric bulk'' outside a
freely moving world brane will remain valid for the case of motion that is
forced by minimal (generalised Wess Zumino type) coupling to an external
antisymmetric gauge field provided its kinetic action contribution has the
usual homogeneous quadratic form. This means that the geometry on each side of
the brane worldsheet will still be of the generalised Schwarzschild anti de
Sitter type. The usual first integrated Friedmann equation for the Hubble
expansion rate can thereby be straightforwardly generalised by inclusion of new
terms involving 2 extra parameters respectively measuring the strength of the
gauge coupling and the degree of deviation from reflection symmetry. Some
conceivable phenomenological implications are briefly outlined, and
corresponding limitations are derived for possible values of relevant
parameters.

\\ ( http://au.arXiv.org/abs/gr-qc/0101010 , 16kb )
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Paper: gr-qc/0101041
From: Neil J. Cornish
Date: Wed, 10 Jan 2001 20:04:05 GMT (3kb)

Title: Comment on "Gravity Waves, Chaos, and Spinning Compact Binaries"
Authors: Neil J. Cornish
Report-no: MSU-PHYS-200075
Journal-ref: Phys. Rev. Lett. 85, 3980 (October 30th, 2000)

Levin (gr-qc/9910040) has shown that spinning compact binaries can be chaotic
at second post-Newtonian order. However, when higher order dissipational
effects are included, the dynamics will no longer be chaotic, though the
evolution may still be unpredictable in a practical sense. I discuss some of
the additional work that needs to be done to decide how this unpredictability
might affect gravitational wave detectors such as LIGO.

\\ ( http://au.arXiv.org/abs/gr-qc/0101041 , 3kb )
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Paper: cond-mat/0101291
From: Reinhard PRIX
Date: Thu, 18 Jan 2001 18:19:42 GMT (9kb)

Title: Relativistic solution of Iordanskii problem in multi-constituent
superfluid mechanics
Authors: Brandon Carter, David Langlois, Reinhard Prix
Comments: 7 pages, LaTeX, Contrib. to "Vortices in Unconventional
Superconductors and Superfluids", Dresden, March 2000, ed. G.Volovik

Flow past a line vortex in a simple perfect fluid or superfluid gives rise to a
transverse Magnus force that is given by the well known Joukowski lift formula.
The problem of generalising this to multiconstituent superfluid models has been
controversial since it was originally posed by the work of Iordanski in the
context of the Landau 2-constituent model for He-4 at finite temperature. The
present work deals not just with this particular case but with the generic
category of perfect multiconstituent models including the kind proposed for a
mixture of He-4 and He-3 by Andreev and Bashkin. It is shown here (using a
relativistic approach) that each constituent will provide a contribution
proportional to the product of the corresponding momentum circulation integral
with the associated asymptotic current density.

\\ ( http://au.arXiv.org/abs/cond-mat/0101291 , 9kb )
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Paper: gr-qc/0102113
From: Brandon CARTER
Date: Wed, 28 Feb 2001 16:02:19 GMT (12kb)

Title: Interaction of gravitational waves with an elastic solid medium
Authors: B. Carter
Comments: 14 pages TeX file of contrib. to proc. Gravitational Radiation, Les
Houches 1982, ed N. Deruelle, T. Piran, 455-464 (North Holland, Amsterdam,
1983)

Contents. 1. Introduction. 2. Kinematics of a Material Medium: Material
Representation. 3. Kinematics of a Material Medium: Convected Differentials. 4.
Kinematics of a Perfect Elastic Medium. 5. Small Gravitational Perturbations of
an Elastic Medium.

\\ ( http://au.arXiv.org/abs/gr-qc/0102113 , 12kb )
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