Subject: ASGRG Newsletter #13
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AUSTRALASIAN SOCIETY FOR GENERAL RELATIVITY AND GRAVITATION
Electronic Newsletter -- #13, Autumn 2004
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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, 2004.
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CONTENTS:
* KERR FEST, University of Canterbury, Christchurch, 26-28 August, 2004
* REPORT ON ACGRG4, Melbourne, 7-9 January, 2004
* MINUTES OF BIENNIAL GENERAL MEETING, Melbourne, 8 January, 2004
* LIFE IN BRUNEI
* GRAVITY PROBE B
* MEMBERSHIP DETAILS ONLINE at
http://www.physics.adelaide.edu.au/ASGRG/members.html
* SUBSCRIPTIONS
* FORTHCOMING MEETINGS
* MEMBERS' ABSTRACTS at gr-qc, December 2003 - May 2004
* ABSTRACTS FROM THE LIGO SCIENTIFIC COLLABORATION at gr-qc,
June 2003 - May 2004
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NOTE: This item is a resend of the first announcement of Kerr Fest, which
all ASGRG members should have received on May 6.
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KERR FEST
Black Holes in Astrophysics, General Relativity & Quantum Gravity
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*A celebration in the year of Roy Kerr's 70th birthday*
University of Canterbury, Christchurch, New Zealand
Thurs 26 - Sat 28, August, 2004
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http://www.phys.canterbury.ac.nz/kerrfest/
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Speakers will include
* Steve Carlip (UC Davis)
* Brandon Carter (Observatoire de Paris, Meudon)
* Andy Fabian (U Cambridge)
* Josh Goldberg (Syracuse U)
* Gary Horowitz (UC Santa Barbara)
* Zoltan Perjes (KFKI Budapest)
* Maurice van Putten (MIT)
* David Robinson (Kings College, London)
* Remo Ruffini (ICRA, U Rome)
* Peter Szekeres (U Adelaide)
* Matt Visser (VUW)
Online registration for the Symposium to mark Roy Kerr's 70th birthday
has NOW OPENED. Please visit the website for further details. For those
of you coming from Australia - we realise it is in term time: however,
we had to make it fit in our own mid-semester break to get accommodation
in student halls, a lecture theatre etc. It should be possible to juggle
your teaching, we hope, to take a couple of days off to come to this
unique event. The welcome function will be held on Thursday, so as so make
the programme as compact as possible for those of you coming from Australia.
NOTE: there are very reasonably priced trans-Tasman airfares (around
A$180-$200 including taxes one way from Melbourne/Sydney to Christchurch)
now that Pacific Blue is operating, and other operators have also lowered
their fares. The fares can be booked on the Internet and there are travel
links on the conference web site.
In addition to the scientific programme there will be a Welcome Reception,
Public Lecture and Conference Banquet which are **all included**
in the registration fee. Early bird registration (at NZ$250) is **due by
16 July, 2004 **.
PROGRAM: We expect talks will begin first thing on Thursday, 26 August
and finish around midday on Saturday 28 August, so most people will plan
to stay for at least the 3 nights of 25th, 26th and 27th August. The
welcome event and public will be on the evening of Thursday 26th,
and the banquet on Friday 27th August.
CONTRIBUTED TALKS:
Contributed talks on the theme of black holes and Roy's scientific
contributions are welcome. While we may take a slightly liberal interpretation
of this, we will vet the contributions to make sure that there is some
point of contact with Roy's work. Please get in early with your abstracts
if possible - this can be done in advance of registering. In any event,
abstracts of any proposed talks should be emailed by 16 July 2004 at the
latest: d.wiltshire@phys.canterbury.ac.nz also by 16 July, 2004.
POST CONFERENCE TOURS: We are not planning any ourselves, but a number of
useful links are given under "Tours" on the webpage.
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REPORT ON ACGRG4, Monash University, Melbourne, January 7-9 2004
The 4th Australasian Conference on General Relativity and Gravitation (ACGRG4)
was held at Monash University in Melbourne, Australia from 7 to 9 January 2004.
ACGRG4 was the fourth in a series of approximately biennial conferences on
general relativity and gravitation organised by the ASGRG.
At total of 36 presentations were given over the three days of ACGRG4,
including plenary talks from David McClelland ("Gravitational wave detection"),
Peter Veitch ("Development of high power lasers for gravitational wave
interferometry"), Mike Ashley ("A heterodyne method for determining the
stability of calibration lines in an interferometer"), Matthew Bailes
("Gravitational wave astrophysics with radio pulsars"), David Wiltshire
("Stable gravastars - An alternative to black holes"), Susan Scott ("Curvature
singularities and abstract boundary singularity theorems for space-time"),
Joey Medved ("Quasinormal modes and 'dirty' black holes"), Robin Tucker
("Relativistic balance laws for Cosserat media in general spacetimes"), and
Michael Hall ("Exact uncertainty approach to quantum mechanics and quantum
gravity").
In addition, David Blair aired a multi-media presentation on the new Gravity
Discovery Centre at Gingin, and Antony Searle demonstrated the ANU's
relativity video.
The more specialised talks were divided into 10 parallel sessions which covered
gravitational wave detection technology, brane world models, relativistic
strings, relativistic cosmology, numerical relativity and an assortment of
problems in mathematical relativity.
The conference dinner was held at the Monash University Staff Club on
the evening of January 8, and was enjoyed by all. Particular thanks
should go to the local organisers (Leo Brewin, Tony Lun, Elizabeth Stark
and Raymond Burston) for making ACGRG4 such a great success.
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MINUTES OF THE 4TH BIENNIAL GENERAL MEETING OF THE ASGRG
held at Monash University, Melbourne, 8 January, 2004
The meeting opened at 4.15 p.m.
[14 ASGRG members were present. At the time of the BGM less than
56 of the members were financial, so the meeting was quorate.]
Apologies: David Blair
1. The minutes of the 3rd Biennial General Meeting, held at the University
of Western Australia, 11 July 2001, were presented to the meeting. Susan
Scott moved that the minutes be accepted, and Antony Searle seconded. The
motion was approved.
2. President's Report: David McClelland gave an upbeat assessment of the
recent fortunes of the general relativity community in Australasia. There
had been some funded ARC support, and the spin-offs from this should help
the ASGRG to attract new members. There had been some new faculty
appointments, and experimental relativity in particular was growing nicely
in Australia. Similarly, with the appointment of David Wiltshire at the
University of Canterbury and Matt Visser at Victoria University in Wellington,
general relativity was flourishing in New Zealand.
One less positive feature was the dearth of international
participation at ACGRG4, particular from North America, but this was
possibly due to the timing of the conference.
David briefly mentioned the most recent activity of the Society,
namely the Relativity Minisymposium attached to the 6th Australia-New
Zealand Mathematics Convention in Sydney in July 2003. Prior to that,
the ASGRG supported the attendance of Barry Barish as a plenary invited
speaker at AIP 2002 (also in Sydney).
The next important event on the Society's calendar was the 2005
AIP Congress, which was to be held in Canberra in February 2005.
The suggestion raised by David at the last BGM that the ASGRG
should become a member of FASTS had not been pursued, and David
was happy for it to lapse. Similarly, no action had yet been taken on
assigning a separate ARC Category Code to general relativity, gravitation
and cosmology. There are no ARC theory grants in gravity at present, and
David believed that the incoming ASGRG President should pursue this
matter more aggressively. Laurie Cram, the ARC programme manager for
gravity-related areas, was about to step down, and we didn't know who
his replacement would be
3. Treasurer's Report: Susan Scott reported that immediately before
the start of ACGRG4 the Society had a total of 70 members, of which
24 were life members, 24 were ordinary members, 3 were retired, 4
were unwaged, and 15 were student members. Five of the 70 members
were female, and 17 were from outside Australia.
The Society's funds had increased slightly from $11,393 in
June 2001 to $12,206 in November 2003. Much of the increase was due
to the AIP meeting in Sydney in July 2002, which returned a profit
of $1500 to the Society.
Another, minor, source of revenue for the Society were the
processing fees for the sale of the ANU's relativity video, which
contributed $50 per video.
Susan reported that many of the ordinary members were in
arrears, and that the Treasurer's job was complicated by the fact
that she had no access to the membership details on the Adelaide
University website. Malcolm Anderson moved that the Treasurer be
given access to the membership details, and Matt Visser seconded.
The motion was approved.
A further problem for the Treasurer was the fact that the
Society's Commonwealth Bank credit card facility had been cancelled
because of low transaction volume. It would cost a minimum of $12
a month to have it reactivated, and even then it would available
through mail-order only, not EFTPOS. The incoming ASGRG Treasurer
was asked to investigate the facilities offered by other financial
institutions.
Antony Searle moved that the incoming Treasurer be requested
to do a quick web search and bring prospective members to the
attention of the ASGRG Committee. Mike Ashley seconded. The motion
was approved.
4. Auditor's Report: The Auditor, John Schuz, stated that he was
satisfied with the Society's accounts and had signed a letter to
that effect. Matt Visser moved that the ASGRG offer a vote of
thanks to John for his work as Auditor, and John Steele seconded.
The motion was approved.
5. Appointment of Auditor for the next session: John Schutz agreed to
remain the Auditor of the Society's accounts.
6. Date and venue for ACGRG5: The meeting decided (tentatively) that
ACGRG5 would be held at the University of Canterbury, Christchurch, in
September 2006. In view of this, the meeting moved to co-opt Matt
Visser as an extraordinary member of the ASGRG Committee.
7. Election of officers: The following people were elected officers of
the ASGRG Committee by acclamation (the mover and seconder are
shown in brackets):
President: Susan Scott (McClelland, Searle)
Treasurer: Antony Searle (McClelland, Scott)
Secretary: Malcolm Anderson (Wiltshire, Visser)
Officer: David Wiltshire (Charlton, Sandeman)
Officer: Peter Veitch (McClelland, Wiltshire)
8. Bid for GR18 in 2007: The meeting voted to bid for GR18 in Sydney
in July 2007. A professional conference organiser would be appointed,
if we won. The Society should also seek legal advice as to whether it
should be incorporated as a non-profit association.
Bronwyn Palmer of the Sydney Convention and Visitors Bureau
gave an outline of the possible bid. The location would be Darling
Harbour (the Sydney Convention and Exhibition Centre), which has 3500
and 1000 seat auditoria. Accommodation would range from $46 a night
(2-star) to $170 a night (5-star). More detailed (and confidential)
budget information was also given.
9. Proceedings of ACGRG4: David McClelland and Susan Scott were made
responsible for co-ordinating the publication of the proceedings of ACGRG4,
which would appear in General Relativity and Gravitation. The deadline
for manuscripts was nominated as May 31, 2004. Only article per talk could
be submitted, but there were no page limits.
10. Other business:
ASGRG members were encouraged to send items of interest in to the Society
newsletter.
David Wiltshire remained in charge of the Society's website.
The meeting closed with a vote of thanks for the outgoing Committee.
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LIFE IN BRUNEI
Malcolm Anderson, ASGRG Secretary
ASGRG members often ask me what it's like to live and work in Brunei. Most
people living outside South-East Asia, I have found, are not even certain
where Brunei is. They know perhaps that the Sultan of Brunei was once reputed
to be the world's richest man, and that the country's wealth rests on oil,
and assume naturally that it must be somewhere in the Middle East. In fact,
Brunei is a tiny enclave on the north coast of the island of Borneo, which
is otherwise divided between Indonesia and Malaysia. Brunei lies on the same
line of longitude as Perth, and is about 5 degrees north of the equator.
With an area of only 5765 square kilometres, Brunei is less than one tenth
the size of Tasmania. Its population is similar to Canberra's (some 330,000)
and is about 67% Malay and 15% Chinese. There are about 50,000 expatriate
workers, the majority of them Indian. Up until the 19th century Brunei was
an independent Malay sultanate, and controlled most of north Borneo. The
British established a protectorate over it in 1888, and if it were not for
the discovery of off-shore oil in 1929 Brunei would now most probably be
just one of the many states of Malaysia.
Oil is of course the mainstay of Brunei's economy. It should be stressed
that Brunei is not actually a major oil producer. It pumps about 180,000
barrels a day, which is less than a quarter of Australia's oil production.
But in view of Brunei's tiny population, and the fact that much of the oil
revenue is used to support what is by Asian standards a generous welfare
system, the country has the highest standard of living in South-East Asia
outside Singapore.
It is difficult to overstate the pervasive (and corrosive) effects that
the government and the oil money have on the economy and society of Brunei.
Almost all adult Malays have jobs for life in the Bruneian public service
(although job levels were frozen in the wake of the 1997 currency crisis,
and youth unemployment is now becoming a matter of concern). And a "job
for life" includes subsidised housing, interest-free car loans and a
generous pension on retirement at age 55.
The housing market is also completely distorted by government subsidies.
For example, the flat I am living in costs $5000 a month (!) to rent.
(The Brunei dollar has roughly the same value as the Australian dollar.)
This is more than my monthly salary, but the university very kindly
pays for all but $130 of it. The net effect is a simple transfer of oil
money from the government to my landlady, who just happens to be the
Sultan's ex-wife.
On a more personal level, life in Brunei is generally very relaxed.
Although Brunei is a Muslim state and there are a number of seemingly
draconian laws on the statute books, these laws are rarely enforced.
Malay women are supposed to wear Muslim headgear and "modest" clothing,
but most women dress no differently from Westerners. The purchase and
public consumption of alcohol is illegal, but it is easily imported
from Malaysia, most restaurants will allow you to bring your own, and
most hotels will happily sell it (although at black market prices).
The University of Brunei Darussalam, where I work, has about 200 staff
and 4000 students (mostly student teachers). I teach two courses a
semester (in calculus, geometry and mechanics), to classes that range
in size from 50 to 150. I also supervise on average two honours project
students a year. All lectures in the Science Faculty are in English,
and more than half of the students are female. Unfortunately the
local students are in general very weak, and have little interest in
any mathematics beyond A-level, as most of them intend to become high-
school maths teachers.
The semesters are 14 weeks long, lasting from August to December, then
January to May. The working week has a "split weekend", as Friday is a
holiday in place of Saturday. I found this arrangement difficult to
adjust to at first, but eventually got used to it. The campus is only
about 10 years old, and boasts some attractive buildings modelled on
traditional Malay architecture, but unfortunately the typical Bruneian
disdain for maintenance means that much of it is already falling apart.
In fact, the sorry state of the infrastructure is probably the only
difficult feature of life in Brunei. The food is cheap, the roads are
ultra-modern, the weather is great, and the wildlife is extraordinarily
varied. Most radio and TV stations are in English, as are most of the
movies in the cinemas. Computer software and video and audio CDs are
all pirated and ridiculously cheap. Singapore, the local centre of
fashion and culture, is only a two-hour flight away. But if you attempt
to make an international phone call, or connect to the internet, or
rely on the water, electricity or air conditioning at home or work,
you often end up frustrated. And it's best to avoid the government
bureaucracy whenever possible - my travel refund when I first arrived
was delayed by 9 months because someone sent my file to "Pensions"
instead of "Passage", and it was only retrieved because I found it
myself...
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GRAVITY PROBE B
Gravity Probe B has finally been launched after being "in the pipeline" for
decades. For more, read on.
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"In Search of Gravitomagnetism", by Tony Phillips, for Science@NASA
Gravity Probe B has left Earth to measure a subtle yet long-sought force of
Nature.
April 20, 2004: NASA's Gravity Probe B spacecraft left Earth today in search
of a force of nature, long suspected but never proven: gravitomagnetism.
Gravitomagnetism is produced by stars and planets when they spin. "It's
similar in form to the magnetic field produced by a spinning ball of charge,"
explains physicist Clifford Will of Washington University (St. Louis).
Replace charge with mass, and magnetism becomes gravitomagnetism.
We don't feel gravitomagnetism as we go about our everyday lives on Earth,
but according to Einstein's theory of General Relativity it's real. When a
planet (or a star or a black hole ... or anything massive) spins it pulls
space and time around with it, an action known as "frame dragging." The
fabric of spacetime twists like a vortex. Einstein tells us that all
gravitational forces correspond to a bending of spacetime; the "twist"
is gravitomagnetism.
What does gravitomagnetism do? "It can make the orbits of satellites
precess," says Will, "and it would cause a gyroscope placed in Earth orbit
to wobble." Both effects are small and difficult to measure.
Researchers led by physicist Ignazio Ciufolini have tried to detect the
gravitomagnetic precession of satellite orbits. For their study, they used
the Laser Geodynamic Satellites, LAGEOS & LAGEOS II, two 60 cm diameter balls
studded with mirrors. Precise laser ranging of the pair allows their orbits
to be monitored. The researchers did find a small amount of precession
consistent (at the 20% level) with gravitomagnetism. But there's a problem:
Earth's equatorial bulge pulls on the satellites, too, and causes a
precession billions of times greater than gravitomagnetism. Did Ciufolini et
al. subtract that huge pull with enough precision to detect gravitomagnetism?
Many scientists accept their results, notes Will, while others are skeptical.
Gravity Probe B, developed by scientists at Stanford University, NASA and
Lockheed Martin, will do the experiment differently, using gyroscopes.
The spacecraft circles Earth in a polar orbit 400 miles high. Onboard are
four gyroscopes, each one a sphere, 1.5 inches in diameter, suspended in
vacuum and spinning ten thousand times per minute. If Einstein's equations
are correct and gravitomagnetism is real, the spinning gyroscopes should
wobble as they orbit the earth. Their spin axes will shift, little by little,
until a year from now they point 42 milli-arcseconds away from where they
started. Gravity Probe B can measure this angle with a precision of 0.5
milli-arcseconds, or about 1%.
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The full text of this article can be found at:
http://science.nasa.gov/headlines/y2004/19apr_gravitomagnetism.htm?list726964
The Gravity Probe B mission homepage is at: http://einstein.stanford.edu/
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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 2004 - June 2005 subscriptions are requested, if you wish to
pay for July 2005 - June 2006 at the same time, it may simplify matters.
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FORTHCOMING MEETINGS
June 2-5, 2004: 11th Hellenic Gravity Meeting
University of the Aegean, Lesbos, Greece
http://www.aegean.gr/marine/XI-NEB/main.htm
June 7-18, 2004: Summer School in Gravitational Wave Astronomy
Center for Gravitational Wave Astronomy
Brownsville, Texas
http://cgwa.phys.utb.edu/outreach/summerschool.php
June 11-12, 2004: 17th Eastern Gravity Meeting
Bowdoin College, Brunswick, Maine
http://www.bowdoin.edu/conferences/egm7/
June 28 - July 3, 2004: 6th Alexander Friedmann International Seminar
on Gravitation and Cosmology
Cargese Institute, Corsica, France
http://www.fisica.ufpb.br/~jfonseca/friedmann/
July 12-15, 2004: 5th LISA Symposium
ESTEC, Noordwijk, The Netherlands
http://www.congrex.nl/04a07/
July 18-23, 2004: 17th International Conference on General Relativity
and Gravitation (GR17)
RDS Convention Centre, Dublin, Ireland
http://www.dcu.ie/~nolanb/gr17.htm
July 25 - August 6, 2004: 11th Brazilian School of Cosmology and Gravitation
Rio de Janeiro, Brazil
http://www.cosmologia.cbpf.br
August 1-7, 2004: "New Geometry of Nature: Mathematics, Physics, Geophysics
and Astronomy"
Kazan State University, Irkutsk, Russia
http://www.ksu.ru/GeoN-Kazan-2003
August 9-16, 2004: "Number, Time and Relativity"
Bauman Moscow State Technical University, Moscow, Russia
http://www.hypercomplex.ru/index_eng.html
August 26-28, 2004: Kerr Fest "Black Holes in Astrophysics, Relativity and
Quantum Gravity"
University of Canterbury, Christchurch, New Zealand
http://www.phys.canterbury.ac.nz/kerrfest/
September 6-7, 2004: Current Themes in Quantum Gravity: A Two-day Conference
in Honour of the 60th Birthday of Chris Isham
Imperial College, London, United KIngdom
http://theory.ic.ac.uk/
September 13-16, 2004: 16th Sigrav Conference on General Relativity and
Gravitational Physics
Vietri sul Mare, Salerno, Italy
http://www.sa.infn.it/sigrav04/
September 17-21, 2004: International Workshop on Particle Physics and the
Early Universe (COSMO-04)
University of Toronto, Canada
http://www.cita.utoronto.ca/%7Ecosmo04/index.shtml
September 20-25, 2004: Summer School on "Structure and Dynamics of Compact Objects"
Albert Einstein Institute, Potsdam, Germany
http://sfb.aei.mpg.de/School04/
September 23-25, 2004: XXVII Spanish Relativity Meeting
Miraflores de la Sierra, Madrid, Spain
http://gesalerico.ft.uam.es/ere2004/ere2004.html
October 15-16, 2004: 14th Midwest Relativity Meeting (MWRM-14)
University of Wisconsin, Milwaukee
http://www.lsc-group.phys.uwm.edu/mwrm14/
December 13-17, 2004: 22nd Texas Symposium
Stanford University, California
http://texasatstanford.slac.stanford.edu/
December 15-18, 2004: 9th Annual Gravitational Wave Data Analysis Workshop
Annecy-le-Vieux Particle Physics Laboratory, Annecy, France
http://lappc-in39.in2p3.fr/GWDAW9/
January 11-14, 2005: International Conference on Relativity (ICR-2005)
Amravati, India
March 29 - 2 April, 2005: "Spacetime in Action: One Hundred Years of Relativity"
Pavia, Italy
April 5-8, 2005: "Geometry and Physics After 100 Years of Einstein's Relativity:
10 Years of the Albert Einstein Institute"
Albert Einstein Institute, Potsdam, Germany
http://www.aei.mpg.de/
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MEMBERS' ABSTRACTS at gr-qc, December 2003 - May 2004
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/0404123
From: John McNabb
Date: Thu, 29 Apr 2004 21:00:28 GMT (199kb)
Overview of the BlockNormal Event Trigger Generator
Authors: J W C McNabb, M Ashley, L S Finn, E Rotthoff, A Stuver,
T Summerscales, P Sutton, M Tibbits, K Thorne, K Zaleski
Comments: GWDAW-8 proceedings, 6 pages, 2 figures
In the search for unmodeled gravitational wave bursts, there are a variety of
methods that have been proposed to generate candidate events from time series
data. Block Normal is a method of identifying candidate events by searching
for places in the data stream where the characteristic statistics of the data
change. These change-points divide the data into blocks in which the
characteristics of the block are stationary. Blocks in which these
characteristics are inconsistent with the long term characteristic statistics
are marked as Event-Triggers which can then be investigated by a more
computationally demanding multi-detector analysis.
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gr-qc/0401068
From: Alan Barnes
Date: Thu, 15 Jan 2004 21:51:42 GMT (7kb)
Purely magnetic spacetimes
Authors: Alan Barnes
Comments: 6 pages, no figures, LaTeX. To appear in the Proceedings of the
27th Spanish Relativity Meeting (Encuentros Relativistas Espanoles), Alicante,
Spain. September,2003
Spacetimes in which the electric part of the Weyl tensor vanishes (relative
to some timelike unit vector field) are said to be purely magnetic. Examples
of purely magnetic spacetimes are known and are relatively easy to construct,
if no restrictions are placed on the energy-momentum tensor. However it has
long been conjectured that purely magnetic vacuum spacetimes (with or without
a cosmological constant) do not exist. The history of this conjecture is
reviewedand some advances made in the last year are described briefly. A
generalisationof this conjecture first suggested for type D vacuum spacetimes
by Ferrando andSaez is stated and proved in a number of special cases.
Finally an approach to a general proof of the conjecture is described using
the Newman-Penrose formalism based on a canonical null tetrad of the Weyl
tensor.
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gr-qc/0402070
From: Robert Bartnik
Date: Mon, 16 Feb 2004 00:51:38 GMT (37kb)
Phase space for the Einstein equations
Authors: Robert Bartnik
Comments: 33 pages, 0 figures, LaTeX2e, submitted to Comm Analysis and
Geometry
A Hilbert manifold structure is described for the ADM phase space of
asymptotically flat initial data $(g,\pi)$ with local $H^2\times H^1$ Sobolev
regularity. Solutions of the constraint equations form a Hilbert submanifold.
A regularized RT Hamiltonian is defined and smooth on the full phase space and
generates the Einstein evolution for any lapse-shift asymptotic to a (time)
translation at infinity. Critical points for the total (ADM) mass, considered
as a function on the Hilbert manifold of constraint solutions, arise precisely
at initial data generating stationary vacuum spacetimes.
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gr-qc/0405092
From: Robert Bartnik
Date: Mon, 17 May 2004 23:35:04 GMT (49kb)
The Constraint Equations
Authors: Robert Bartnik, Jim Isenberg
Comments: 34 pages, LaTeX, to appear in the proceedings of the 2002 Cargese
meeting "50 Years of the Cauchy Problem, in honour of Y. Choquet-Bruhat",
editors P.T.Chru\'sciel and H. Friedrich
We review the properties of the constraint equations, from their geometric
origin in hypersurface geometry through to their roles in the Cauchy problem
and the Hamiltonian formulation of the Einstein equations. We then review
properties of the space of solutions and construction techniques, including
the conformal and conformal thin sandwich methods, the thin sandwich method,
quasi-spherical and generalized QS methods, gluing techniques and the
Corvino-Schoen projection.
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gr-qc/0404129
From: Jefferson Crowder
Date (v1): Fri, 30 Apr 2004 18:01:21 GMT (31kb)
Date (revised v2): Mon, 3 May 2004 21:34:54 GMT (31kb)
LISA Source Confusion
Authors: Jeff Crowder, Neil J. Cornish
Comments: 8 pages, 14 figures
The Laser Interferometer Space Antenna (LISA) will detect thousands of
gravitational wave sources. Many of these sources will be overlapping in the
sense that their signals will have a non-zero cross-correlation. Such
overlaps lead to source confusion, which adversely affects how well we can
extract information about the individual sources. Here we study how source
confusion impacts parameter estimation for galactic compact binaries, with
emphasis on the effects of the number of overlaping sources, the time of
observation, the gravitational wave frequencies of the sources, and the
degree of the signal correlations. Our main findings are that the parameter
resolution decays exponentially with the number of overlapping sources, and
super-exponentially with the degree of cross-correlation. We also find that
an extended mission lifetime is key to disentangling the source confusion as
the parameter resolution for overlapping sources improves much faster than
the usual square root of the observation time.
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gr-qc/0312042
From: Neil J. Cornish
Date: Sun, 7 Dec 2003 21:59:19 GMT (14kb)
Rapid LISA Astronomy
Authors: Neil J. Cornish
Comments: 4 Pages, 2 Figures, RevTex
A simple method is presented for removing the amplitude, frequency and phase
modulations from the Laser Interferometer Space Antenna (LISA) data stream
for sources at any sky location. When combined with an excess power trigger
or the fast chirp transform, the total demodulation procedure allows the
majority of LISA sources to be identified without recourse to matched
filtering.
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gr-qc/0402042
From: Antony Searle
Date: Tue, 10 Feb 2004 00:50:10 GMT (5kb)
The ACIGA Data Analysis programme
Authors: Susan M Scott, Antony C Searle, Benedict J Cusack, David E McClelland
Comments: 10 pages, 0 figures, accepted, Classical and Quantum Gravity,
(Proceedings of the 5th Edoardo Amaldi Conference on Gravitational Waves,
Tirrenia, Pisa, Italy, 6-11 July 2003)
Journal-ref: Class.Quant.Grav. 21 (2004) S853-S856
The Data Analysis programme of the Australian Consortium for Interferometric
Gravitational Astronomy (ACIGA) was set up in 1998 by the first author to
complement the then existing ACIGA programmes working on suspension systems,
lasers and optics, and detector configurations. The ACIGA Data Analysis
programme continues to contribute significantly in the field; we present an
overview of our activities.
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gr-qc/0403031
From: John Steele
Date: Sun, 7 Mar 2004 21:49:37 GMT (28kb)
Calculating Symmetries in Newman-Tamburino metrics
Authors: John D. Steele
In this paper I show that the Newman-Tamburino spherical metrics always admit
a Killing vector, correcting a claim by Collinson and French, (1967 J. Math.
Phys. 8 701) and also admit a homothety. A similar calculation is given for
the limit of the Newman-Tamburino cylindrical metric.
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gr-qc/0402069
From: Matt Visser
Date (v1): Sun, 15 Feb 2004 21:33:53 GMT (16kb)
Date (revised v2): Sun, 22 Feb 2004 21:23:25 GMT (16kb)
Dirty black holes: Spacetime geometry and near-horizon symmetries
Authors: A J M Medved, Damien Martin, Matt Visser
Comments: 23 pages, plain LaTeX. V2: Discussion regarding extremal horizons
corrected. Two references addded. No other physics changes
We consider the spacetime geometry of a static but otherwise generic black
hole (that is, the horizon geometry and topology are not necessarily
spherically symmetric). It is demonstrated, by purely geometrical techniques,
that the curvature tensors, and the Einstein tensor in particular, exhibit a
very high degree of symmetry as the horizon is approached. Consequently, the
stress-energy tensor will be highly constrained near any static Killing
horizon. More specifically, it is shown that -- at the horizon -- the
stress-energy tensor block-diagonalizes into "transverse" and "parallel"
blocks, the transverse components of this tensor are proportional to the
transverse metric, and these properties remain invariant under static
conformal deformations. Moreover, we speculate that this geometric symmetry
underlies Carlip's notion of an asymptotic near-horizon conformal symmetry
controlling the entropy of a black hole.
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gr-qc/0403026
From: Matt Visser
Date: Fri, 5 Mar 2004 05:52:52 GMT (16kb)
Dirty black holes: Symmetries at stationary non-static horizons
Authors: A J M Medved, Damien Martin, Matt Visser
Comments: 21 pages; plain LaTeX
We establish that the Einstein tensor takes on a highly symmetric form near
the Killing horizon of any stationary but non-static (and non-extremal) black
hole spacetime. [This follows up on a recent article by the current authors,
gr-qc/0402069, which considered static black holes.] Specifically, at any such
Killing horizon -- irrespective of the horizon geometry -- the Einstein tensor
block-diagonalizes into "transverse" and "parallel" blocks, and its transverse
components are proportional to the transverse metric. Our findings are
supported by two independent procedures; one based on the regularity of the
on-horizon geometry and another that directly utilizes the elegant nature of
a bifurcate Killing horizon. It is then argued that geometrical symmetries
will severely constrain the matter near any Killing horizon. We also speculate
on how this may be relevant to certain calculations of the black hole entropy.
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astro-ph/0403336
From: Matt Visser
Date: Mon, 15 Mar 2004 04:50:43 GMT (10kb)
Power-laws from critical gravitational collapse: The mass distribution of
subsolar objects
Authors: Matt Visser (Victoria University of Wellington) Nicolas Yunes
(Pennsylvania State University)
Comments: 12 pages: plain LaTeX
Report-no: CGPG-03/10-6
Critical gravitational collapse and self similarity are used to probe the
mass distribution of subsolar objects. We demonstrate that at very low mass
the distribution is given by a power law, with an exponent opposite in sign
to that observed at high-mass regime. We further show that the value of this
low-mass exponent is in principle calculable via dynamical systems theory
applied to gravitational collapse. Qualitative agreement between numerical
experiments and observational data is good.
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astro-ph/0404434
From: Matt Visser
Date: Wed, 21 Apr 2004 22:21:49 GMT (14kb)
Universality of the subsolar mass distribution from critical gravitational
collapse
Authors: Matt Visser (Victoria University of Wellington), Nicolas Yunes
(Pennsylvania State University)
Comments: 17 pages, uses aastex
Self-similarity induced by critical gravitational collapse is used as a
paradigm to probe the mass distribution of subsolar objects. At large mass
(solar mass and above) there is widespread agreement as to both the form
and parameter values arising in the mass distribution of stellar objects.
At subsolar mass there is still considerable disagreement as to the
qualitative form of the mass distribution, let alone the specific parameter
values characterizing that distribution. For the first time, the paradigm
of critical gravitational collapse is applied to several concrete
astrophysical scenarios to derive robust qualitative features of the
subsolar mass distribution. We further contrast these theoretically derived
ideas with the observational situation. In particular, we demonstrate that
at very low mass the distribution is given by a power law, with an exponent
opposite in sign to that observed in the high-mass regime. The value of
this low-mass exponent is in principle calculable via dynamical systems
theory applied to gravitational collapse. Qualitative agreement between
theory, numerical experiments, and observational data is good, though
quantitative issues remain troublesome.
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gr-qc/0405103
From: Sayan Kar
Date: Wed, 19 May 2004 09:43:30 GMT (7kb)
Quantifying energy condition violations in traversable wormholes
Authors: Sayan Kar (IITKgp, India), Naresh Dadhich (IUCAA, India),
Matt Visser (Victoria University of Wellington, New Zealand)
Comments: 8 pages, no figures, to appear in Proceedings of ICGC04, Cochin,
India (January 5-10,2004)
The 'theoretical' existence of traversable Lorentzian wormholes in the
classical, macroscopic world is plagued by the violation of the well-known
energy conditions of General Relativity. In this brief article we show :
(i) how the extent of violation can be quantified using certain volume
integrals (ii) whether this 'amount of violation' can be minimised for
some specific cut-and-paste geometric constructions. Examples and
possibilities are also outlined.
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gr-qc/0403093
From: Albert Lazzarini
Date: Tue, 23 Mar 2004 01:49:47 GMT (373kb)
Optimal combination of signals from co-located gravitational wave
interferometers for use in searches for a stochastic background
Authors: A. Lazzarini, S. Bose, P. Fritschel, M. McHugh, T. Regimbau,
K. Reilly, J.D. Romano, J. T. Whelan, S. Whitcomb, B. F. Whiting
Comments: 14 pages, 4 figures, submitted to Physical Review D
This article derives an optimal (i.e., unbiased, minimum variance) estimator
for the pseudo-detector strain for a pair of co-located gravitational wave
interferometers (such as the pair of LIGO interferometers at its Hanford
Observatory), allowing for possible instrumental correlations between the
two detectors. The technique is robust and does not involve any assumptions
or approximations regarding the relative strength of gravitational wave
signals in the detector pair with respect to other sources of correlated
instrumental or environmental noise. An expression is given for the effective
power spectral density of the combined noise in the pseudo-detector. This
can then be introduced into the standard optimal Wiener filter used to
cross-correlate detector data streams in order to obtain an optimal estimate
of the stochastic gravitational wave background. In addition, a dual to the
optimal estimate of strain is derived. This dual is constructed to contain
no gravitational wave signature and can thus be used as on "off-source"
measurement to test algorithms used in the "on-source" observation.
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gr-qc/0405138
From: Chengmin Zhang
Date: Fri, 28 May 2004 14:22:08 GMT (64kb)
Dirac Spin Precession in Kerr Spacetime by the parallelism description
Authors: C.M. Zhang
Comments: 6 pages
In the framework of parallelism general relativity (PGR), the Dirac particle
spin precession in the rotational gravitational field is studied. In terms
of the equivalent tetrad of Kerr frame, we investigate the torsion
axial-vector spin coupling in PGR. In the case of the weak field and slow
rotation approximation, we obtain that the torsion axial-vector has the
dipole-like structure, but different from the gravitomagnetic field, which
indicates that the choice of the Kerr tetrad will influence on the physics
interpretation of the axial-vector spin coupling.
******************************************************************************
ABSTRACTS FROM THE LIGO SCIENTIFIC COLLABORATION at gr-qc, June 2003 - May 2004
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.
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gr-qc/0308043
From: David Shoemaker
Date (v1): Thu, 14 Aug 2003 12:40:21 GMT (641kb)
Date (revised v2): Fri, 15 Aug 2003 21:44:22 GMT (641kb)
Date (revised v3): Wed, 17 Sep 2003 18:58:22 GMT (643kb)
Detector Description and Performance for the First Coincidence Observations
between LIGO and GEO
Authors: The LIGO Scientific Collaboration: B. Abbott, et al
Comments: 41 pages, 9 figures 17 Sept 03: author list amended, minor
editorial changes
Journal-ref: Nucl.Instrum.Meth. A517 (2004) 154-179
For 17 days in August and September 2002, the LIGO and GEO interferometer
gravitational wave detectors were operated in coincidence to produce their
first data for scientific analysis. Although the detectors were still far
from their design sensitivity levels, the data can be used to place better
upper limits on the flux of gravitational waves incident on the earth than
previous direct measurements. This paper describes the instruments and the
data in some detail, as a companion to analysis papers based on the first
data.
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gr-qc/0308050
From: M. Alessandra Papa
Date: Thu, 14 Aug 2003 22:31:14 GMT (479kb)
Setting upper limits on the strength of periodic gravitational waves using
the first science data from the GEO600 and LIGO detectors
Authors: The LIGO Scientific Collaboration: B.Abbott, et al
Comments: 16 pages,8 figures
Report-no: LIGO-P030008-E-Z
Journal-ref: Phys.Rev. D69 (2004) 082004
Data collected by the GEO600 and LIGO interferometric gravitational wave
detectors during their first observational science run were searched for
continuous gravitational waves from the pulsar J1939+2134 at twice its
rotation frequency. Two independent analysis methods were used and are
demonstrated in this paper: a frequency domain method and a time domain
method. Both achieve consistent null results, placing new upper limits on
the strength of the pulsar's gravitational wave emission. A model emission
mechanism is used to interpret the limits as a constraint on the pulsar's
equatorial ellipticity.
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gr-qc/0308069
From: Patrick Brady
Date: Thu, 21 Aug 2003 13:58:21 GMT (460kb)
Analysis of LIGO data for gravitational waves from binary neutron stars
Authors: The LIGO Scientific Collaboration: B.Abbott, et al
Comments: 17 pages, 9 figures
We report on a search for gravitational waves from coalescing compact binary
systems in the Milky Way and the Magellanic Clouds. The analysis uses data
taken by two of the three LIGO interferometers during the first LIGO science
run and illustrates a method of setting upper limits on inspiral event rates
using interferometer data. The analysis pipeline is described with particular
attention to data selection and coincidence between the two interferometers.
We establish an observational upper limit of $\mathcal{R}<$1.7 \times 10^{2}$
per year per Milky Way Equivalent Galaxy (MWEG), with 90% confidence, on the
coalescence rate of binary systems in which each component has a mass in the
range 1-3 $M_\odot$.
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gr-qc/0312056
From: Alan J. Weinstein
Date (v1): Tue, 9 Dec 2003 19:19:30 GMT (139kb)
Date (revised v2): Wed, 10 Dec 2003 03:56:48 GMT (139kb)
Date (revised v3): Tue, 6 Jan 2004 18:15:35 GMT (139kb)
Date (revised v4): Tue, 30 Mar 2004 17:59:20 GMT (140kb)
First upper limits from LIGO on gravitational wave bursts
Authors: LIGO Scientific Collaboration: B. Abbott, et al
Comments: 21 pages, 15 figures, accepted by Phys Rev D. Fixed a few small
typos and updated a few references
Report-no: LIGO-P030011
Journal-ref: Phys.Rev.D (2004)
We report on a search for gravitational wave bursts using data from the first
science run of the LIGO detectors. Our search focuses on bursts with
durations ranging from 4 ms to 100 ms, and with significant power in the LIGO
sensitivityband of 150 to 3000 Hz. We bound the rate for such detected bursts
at less than1.6 events per day at 90% confidence level. This result is
interpreted in termsof the detection efficiency for ad hoc waveforms
(Gaussians and sine-Gaussians)as a function of their root-sum-square strain
h_{rss}; typical sensitivities lie in the range h_{rss} ~ 10^{-19} - 10^{-17}
strain/rtHz, depending on waveform. We discuss improvements in the search
method that will be applied to future science data from LIGO and other
gravitational wave detectors.
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gr-qc/0312088
From: Joseph Romano
Date: Fri, 19 Dec 2003 18:00:01 GMT (723kb)
Analysis of First LIGO Science Data for Stochastic Gravitational Waves
Authors: LIGO Scientific Collaboration: B. Abbott, et al
Comments: 26 pages, 17 figures
We present the analysis of between 50 and 100 hrs of coincident
interferometric strain data used to search for and establish an upper limit
on a stochastic background of gravitational radiation. These data come from
the first LIGO science run, during which all three LIGO interferometers were
operated over a 2-week period spanning August and September of 2002. The
method of cross-correlating the outputs of two interferometers is used for
analysis. We describe in detail practical signal processing issues that arise
when working with real data, and we establish an observational upper limit on
a f^{-3} power spectrum of gravitational waves. Our 90% confidence limit is
Omega_0 h_{100}^2 < 23 in the frequency band 40 to 314 Hz, where h_{100} is
the Hubble constant in units of 100 km/sec/Mpc and Omega_0 is the gravitational
wave energy density per logarithmic frequency interval in units of the closure
density. This limit is approximately 10^4 times better than the previous,
broadband direct limit using interferometric detectors, and nearly 3 times
better than the best narrow-band bar detector limit. As LIGO and other
worldwide detectors improve in sensitivity and attain their design goals, the
analysis procedures described here should lead to stochastic background
sensitivity levels of astrophysical interest.
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