The result may be viewed on the ASGRG home page at
http://www2.phys.canterbury.ac.nz/ASGRG/
Talks covered such wide-ranging ground as invariants of the Riemann tensor, perfect fluid and shear-free cosmologies and ultra-relativistic fluid dynamics, isotropic singularities, numerical relativity and gravitational radiation, Regge calculus, symmetry techniques applied to differential equations in relativity, black hole perturbations and thermodynamics, the thorny topic of signature change, an axiomatic approach to spacetime structure and computer tools for visualising geometry in relativity. The workshop finished with a joint talk by Colin and his student Khai Vu on "Desolv: a MAPLE package for solving differential equations".
Highlights were the talks by Colin's former students Graeme Sneddon, Leo Brewin and Tony Lun, which gave a glimpse of the enormous work that Colin has done for Australian relativity in building up the group at Monash and in encouraging networking among the various groups in Australia. A number of anecdotes these speakers told vividly reflected the vitality of the group that Colin has built up. We wish Colin all the best in his early retirement to undertake fulltime church activities, and hope that he will still find occasions to drop in on our conferences and maintain some contact with the scene that he has contributed so much to.
Proceedings of
THE FIRST AUSTRALASIAN CONFERENCE ON
GENERAL RELATIVITY AND GRAVITATION
12-17 February, 1996, Institute for Theoretical Physics,
University of Adelaide, South Australia.
Editor D.L. Wiltshire
Published by Institute for Theoretical Physics, University of Adelaide, 1996.
ISBN: 0-86396-430-3. 242 + vi pp. Paperback.
Price A$ 20 (approx US $16), credit card payments accepted.
To order click here.
Contains 22 articles on classical relativity, numerical relativity, quantum
gravity and gravitational wave detection.
CONTENTS
GRAVITATIONAL WAVE DETECTION
* A cosmological background of gravitational waves produced by supernovae in
the early universe ... D.G. Blair and L. Ju
* The development of technology for high performance laser interferometer
gravitational wave detectors at the UWA ... C.N. Zhao et al.
NUMERICAL RELATIVITY
* Post-Newtonian smooth particle hydrodynamics
... M.C. Thompson and J.J. Monaghan
* Einstein equations in the null quasi-spherical gauge: Progress report
... Robert Bartnik
* Spectral collocation methods for solution of Einstein's equations in null
quasi-spherical coordinates ... Andrew H. Norton
* Computational methods in the physical interpretation of Robinson-Trautman
spacetimes ... Daniel A. Prager and Anthony W.C. Lun
* Using Riemann normal coordinates in numerical relativity
... Leo Brewin
* An application of Regge calculus to axisymmetric initial data
... A.P. Gentle and L.C. Brewin
MATHEMATICAL RELATIVITY AND CLASSICAL GRAVITATION
* The cosmological singularity
... Peter Szekeres
* The gravitational effects of cusps on cosmic strings
... Malcolm R. Anderson
* Square of general relativity
... D.V. Gal'tsov
* Remarks on the Yilmaz and Alley papers
... Edward D. Fackerell
* On the key functions of axisymmetric gravitation
... P.C. Waylen
* Debye potentials for the massless Dirac equation in algebraically special
spacetimes ... Philip Charlton
* Gauge invariant perturbations of black holes using the modified
Newman-Penrose formalism ... Joe F.Q. Fernandes and Anthony W.C. Lun
QUANTUM GRAVITY
* How wrinkled is the surface of a black hole?
... Rafael D. Sorkin
* Quantum cosmology, supersymmetry, and the problem of time
... Hugh Luckock
* Solving the fine-tuning problem of inflation
... Andrew Matacz
* Quantum gravity: A brief review
... Tze-Chuen Toh
* Holonomies in quantum gravity
... E.E. Wood
* Pregeometric modelling of the spacetime phenomenon
... Reginald T. Cahill and Christopher M. Klinger
* Polarisation of instantons in the SO(4) gauge theory results in gravity
... M.Yu. Kuchiev
(Order from World Scientific or your local distributor)
COSMOLOGY: THE PHYSICS OF THE UNIVERSE
Proceedings of the 8th Physics Summer School,
Australian National University, 16 January - 3 February, 1995
Editors B. Robson, N. Visvanathan and W.S. Woolcock
Published by World Scientific, Singapore, 1996.
ISBN: 981-02-2513-X. 531 + x pages. Price: US$ 82.50. Hardcover.
CONTENTS:
* Introduction to General Relativity ... M.R. Anderson
* Classical Cosmology ... G. Boerner
* Particle Physics Applied to Cosmology ... J. Ellis
* Dark Matter in Galaxies ... K.C. Freeman
* High Red-Shift Galaxies ... R.W. Hunstead
* The Very Early Universe ... V.N. Lukash
* The Hubble Constant and the Age of the Universe ... J. Mould
* Topological Defects ... S.J. Poletti
* Cosmological Implications of Nuclear Physics ... D.N. Schramm, C. Copi and
X. Shi
* The Epoch of Galaxy Formation ... J. Silk
* Statistical Aspects of Large Scale Structure ... A.S. Szalay
* Gravitational Lensing ... R. Webster and D. Mortlock
* An Introduction to Quantum Cosmology ... D.L. Wiltshire
N.B. The Australasian mirror for the Los Alamos archive is now operational at
-------------------------------------------------------------------------------
\\
Paper: gr-qc/9605018
From: phrtc@cc.flinders.edu.au (<phrtc@cc.flinders.edu.au>)
Date: Thu, 09 May 96 15:58:46 +0930
Title: Pregeometric modelling of the spacetime phenomenology
Authors: Reginald T. Cahill, Christopher M. Klinger (Dept. of Physics, Flinders
University)
Comments: 13 page LateX, no figures
Journal-ref: Phys.Lett. A223 (1996) 313-319
\\
At present we have only the very successful but phenomenological Einstein
geometrical modelling of the spacetime phenomenon. This geometrical model
provides a `container' for other theories, in particular the quantum field
theories. Here we report progress in developing a {\em Heraclitean Quantum
System}. This is a particular pregeometric theory for space and time in which
no classical or geometric structures are assumed, but rather the emergence of
such phenomena is sought.
\\
-------------------------------------------------------------------------------
\\
Paper: gr-qc/9605029
From: Neil Cornish <cornish@makarova.ph.unimelb.edu.au>
Date: Thu, 16 May 1996 21:15:51 +1000
Title: The mixmaster universe is chaotic
Authors: Neil J. Cornish (Uni. Melbourne) and Janna J. Levin (UC, Berkeley)
Comments: 4 pages, RevTeX, 3 figures included
Report-no: UM-P-96/33, CfPA-96-TH-10
\\
For the past decade there has been a considerable debate about the existence
of chaos in the mixmaster cosmological model. The debate has been hampered by
the coordinate, or observer dependence of standard chaotic indicators such as
Lyapanov exponents. Here we use coordinate independent, fractal methods to show
the mixmaster universe is indeed chaotic.
\\
------------------------------------------------------------------------------
\\
Paper: gr-qc/9606021
From: Neil Cornish <cornish@makarova.ph.unimelb.edu.au>
Date: Tue, 11 Jun 1996 22:10:58 +1000 (148kb)
Date (revised): Wed, 29 Jan 1997 00:42:15 +1100
Title: The Princess and the Pea
Authors: Neil Cornish (DAMTP, Cambridge), Norm Frankel (Univ. Melbourne)
Comments: 5 pages, RevTeX, 6 figures, revised and expanded version
Report-no: UM-P-96/45
\\
Like a fairy-tale princess, trajectories around black holes can be sensitive
to small disturbances. We describe how a small disturbance can lead to erratic
orbits and an increased production of gravitational waves.
------------------------------------------------------------------------------
\\
Paper: gr-qc/9609016
From: Neil Cornish <cornish@physics.unimelb.EDU.AU>
Date: Sat, 7 Sep 1996 03:05:39 +1000
Title: The black hole that went away
Authors: Neil J. Cornish (Uni. of Melbourne)
Comments: 1 page, RevTeX, no figures
Report-no: UM-P-96/74
\\
A purported black hole solution in (2+1)-dimensions is shown to be nothing
more than flat space viewed from an accelerated frame.
\\
------------------------------------------------------------------------------
\\
Paper: hep-th/9610033
From: Steven Brumby <spb@physics.unimelb.EDU.AU>
Date: Mon, 7 Oct 1996 20:48:19 +1000
Title: Global effects in quaternionic quantum field theory
Authors: S.P. Brumby and G.C. Joshi (Melbourne Uni.)
Comments: 11 pages, no figures, revtex
Report-no: UM-P-96/88; RCHEP 96/11
\\
We present some striking global consequences of a model quaternionic quantum
field theory which is locally complex. We show how making the quaternionic
structure a dynamical quantity naturally leads to the prediction of cosmic
strings and non-baryonic hot dark matter candidates.
\\
------------------------------------------------------------------------------
\\
Paper: gr-qc/9610037
From: Jonathan Kress <jkress@frey.newcastle.edu.au>
Date: Wed, 16 Oct 1996 20:13:27 MDT
Title: Debye Potentials for Maxwell and Dirac Fields from a Generalisation of
the Killing-Yano Equation
Authors: I. M. Benn, Philip Charlton and Jonathan Kress
Comments: 35 pages, plain TeX
\\
By using conformal Killing-Yano tensors, and their generalisations, we obtain
scalar potentials for both the source-free Maxwell and massless Dirac
equations. For each of these equations we construct, from conformal
Killing-Yano tensors, symmetry operators that map any solution to another.
\\
------------------------------------------------------------------------------
\\
Paper: hep-th/9610194
From: Hilary Booth <hilary@neumann.une.edu.au>
Date: Fri, 25 Oct 1996 09:26:24 +1000 (EST)
Title: The Dirac-Maxwell Equations with Cylindrical Symmetry
Authors: Hilary Booth, Chris Radford (University of New England, Australia)
Comments: 17 pages, Latex, 5 figures, psfig, to be published in J. Maths Phys
Report-no: 96-125
\\
A reduction of the Dirac-Maxwell equations in the case of static cylindrical
symmetry is performed. The behaviour of the resulting system of o.d.e.'s is
examined analytically and numerical solutions presented. There are two classes
of solutions.
The first type of solution is a Dirac field surrounding a charged "wire". The
Dirac field is highly localised, concentrated in cylindrical shells about the
wire. A comparison with the usual linearized theory demonstrates that this
localization is entirely due to the non-linearities in the equations which
result from the inclusion of the "self-field".
The second class of solutions have the electrostatic potential finite along
the axis of symmetry but unbounded at large distances from the axis.
\\
------------------------------------------------------------------------------
\\
Paper: hep-th/9610210
From: Steven Brumby <spb@physics.unimelb.EDU.AU>
Date: Mon, 28 Oct 1996 17:25:00 +1000
Title: Implications of quaternionic dark matter
Authors: S.P. Brumby, B.E. Hanlon and G.C. Joshi (Melbourne Uni.)
Comments: 14 pages, RevTeX, no figures
Report-no: UM-P-96/90; RCHEP 96/12
\\
Taking the complex nature of quantum mechanics which we observe today as a
low energy effect of a broken quaternionic theory we explore the possibility
that dark matter arises as a consequence of this underlying quaternionic
structure to our universe. We introduce a low energy, effective, Lagrangian
which incorporates the remnants of a local quaternionic algebra, investigate
the stellar production of the resultant exotic bosons and explore the possible
low energy consequences of our remnant extended Hilbert space.
\\
------------------------------------------------------------------------------
\\
Paper: gr-qc/9611045
From: Robert Bartnik <bartnik@willow.canberra.edu.au>
Date: Fri, 15 Nov 96 15:15:17 GMT
Date (revised): Thu, 29 May 1997 17:10:14 MDT
Title: Einstein equations in the null quasi-spherical gauge
Authors: Robert Bartnik (University of Canberra)
Comments: 12 pages, LaTeX (revtex, amssymb), revision 18 pages, contains
expanded discussion and explanations, updated references
Journal-ref: Class.Quant.Grav. 14 (1997) 2185-2194
\\
The structure of the full Einstein equations in a coordinate gauge based on
expanding null hypersurfaces foliated by metric 2-spheres is explored. The
simple form of the resulting equations has many applications -- in the present
paper we describe the structure of timelike boundary conditions; the matching
problem across null hypersurfaces; and the propagation of gravitational shocks.
\\
------------------------------------------------------------------------------
\\
Paper: gr-qc/9611063
From: andrewm@maths.su.oz.au
Date: Wed, 27 Nov 96 10:29:14 +1100
Date (revised): Wed, 04 Dec 96 15:38:07 +1100
Title: Inflation and the Fine-Tuning Problem
Author: Andrew Matacz (University of Sydney, Australia)
Comments: 5 pages in Latex (uses Revtex), no figures. Minor changes to the text
only
\\
I describe a recently derived stochastic approach to inflaton dynamics which
can address some serious problems associated with conventional inflationary
theory. Using this theory I derive an exact solution to the stochastic dynamics
for the case of a $\lambda\phi^4$ potential and use it to study the generated
primordial density fluctuations. It is found that on both sub and super-horizon
scales the theory predicts gaussian fluctuations to a very high accuracy along
with a near scale-invariant spectrum. Of most interest is that the amplitude
constraint is found to be satisfied for $\lambda\sim 10^{-5}$ rather than
$\lambda\sim 10^{-14}$ of the conventional theory. This represents a dramatic
easing of the fine-tuning constraints, a feature likely to generalize to a wide
range of potentials.
\\
------------------------------------------------------------------------------
\\
Paper: gr-qc/9612011
From: Philip Charlton <philipc@frey.newcastle.edu.au>
Date: Tue, 3 Dec 1996 22:00:23 MST
Title: Dirac symmetry operators from conformal Killing-Yano tensors
Authors: I. M. Benn and Philip Charlton
Comments: 8 pages, TeX
Report-no: 96/28
\\
We show how, for all dimensions and signatures, a symmetry operator for the
massless Dirac equation can be constructed from a conformal Killing-Yano tensor
of arbitrary degree.
\\
------------------------------------------------------------------------------
\\
Paper: quant-ph/9612016
From: Don Koks <dkoks@physics.adelaide.edu.au>
Date: Tue, 3 Dec 1996 14:11:51 +1030 (CST)
Title: Entropy and Uncertainty of Squeezed Quantum Open Systems
Authors: D. Koks, A. Matacz and B.L. Hu
Comments: 36 pages, epsfig, 2 in-text figures included
Report-no: ADP-96-42/M50, umdpp 97-63, School of Mathematics and Statistics
96-41
\\
We define the entropy S and uncertainty function of a squeezed system
interacting with a thermal bath, and study how they change in time by following
the evolution of the reduced density matrix in the influence functional
formalism. As examples, we calculate the entropy of two exactly solvable
squeezed systems: an inverted harmonic oscillator and a scalar field mode
evolving in an inflationary universe. For the inverted oscillator with weak
coupling to the bath, at both high and low temperatures, $S\to r $, where r is
the squeeze parameter. In the de Sitter case, at high temperatures, $S\to
(1-c)r$ where $c = \gamma_0/H$, $\gamma_0$ being the coupling to the bath and H
the Hubble constant. These three cases confirm previous results based on more
ad hoc prescriptions for calculating entropy. But at low temperatures, the de
Sitter entropy $S\to (1/2-c)r$ is noticeably different. This result, obtained
from a more rigorous approach, shows that factors usually ignored by the
conventional approaches, i.e., the nature of the environment and the coupling
strength betwen the system and the environment, are important.
\\
------------------------------------------------------------------------------
\\
Paper: gr-qc/9701046
From: David Hartley <DHartley@physics.adelaide.edu.au>
Date: Tue, 21 Jan 1997 14:12:02 +1030
Title: Tensor distributions on signature-changing space-times
Authors: David Hartley, Robin W. Tucker, Philip A. Tuckey, Tevian Dray
Comments: 9 pages, LaTeX 2.09
Report-no: ADP 96-41/M49
\\
Irregularities in the metric tensor of a signature-changing space-time
suggest that field equations on such space-times might be regarded as
distributional. We review the formalism of tensor distributions on
differentiable manifolds, and examine to what extent rigorous meaning can be
given to field equations in the presence of signature-change, in particular
those involving covariant derivatives. We find that, for both continuous and
discontinuous signature-change, covariant differentiation can be defined on a
class of tensor distributions wide enough to be physically interesting.
\\ (http://xxx.adelaide.edu.au/abs/gr-qc/9701046 , 11kb)
------------------------------------------------------------------------------
\\
Paper: gr-qc/9701057
From: Leo Brewin <leo@newton.maths.monash.edu.au>
Date: Tue, 28 Jan 1997 01:00:24 MST (195kb)
Title: Riemann Normal Coordinates, Smooth Lattices and Numerical Relativity
Authors: Leo Brewin
Comments: 49 pages, 18 epsf figures, plain tex
\\
A new lattice based scheme for numerical relativity will be presented. The
scheme uses the same data as would be used in the Regge calculus (eg. a set of
leg lengths on a simplicial lattice) but it differs significantly in the way
that the field equations are computed. In the new method the standard Einstein
field equations are applied directly to the lattice. This is done by using
locally defined Riemann normal coordinates to interpolate a smooth metric over
local groups of cells of the lattice. Results for the time symmetric initial
data for the Schwarzschild spacetime will be presented. It will be shown that
the scheme yields second order accurate estimates (in the lattice spacing) for
the metric and the curvature. It will also be shown that the Bianchi identities
play an essential role in the construction of the Schwarzschild initial data.
\\ ( http://xxx.adelaide.edu.au/abs/gr-qc/9701057 , 195kb)
------------------------------------------------------------------------------
\\
Paper: hep-th/9702070
From: Simon Davis <simond@maths.su.oz.au>
Date: Sun, 9 Feb 1997 13:29:22 +1100 (EST) (31kb)
Title: Scalar Field Theory in Curved Space and the Definition of Momentum
Author: Simon Davis
Comments: 41 pages, TeX, 3 figures
Report-no: DAMTP-R/96/8
\\
Some general remarks are made about the quantum theory of scalar fields and
the definition of momentum in curved space. Special emphasis is given to field
theory in anti-de Sitter space, as it represents a maximally symmetric
space-time of constant curvature which could arise in the local description of
matter interactions in the small regions of space-time. Transform space rules
for evaluating Feynman diagrams in Euclidean anti-de Sitter space are initially
defined using eigenfunctions based on generalized plane waves. It is shown
that, for a general curved space, the rules associated with the vertex are
dependent on the type of interaction being considered. A condition for
eliminating this dependence is given. It is demonstrated that the vacuum and
propagator in conformally flat coordinates in anti-de Sitter space are
equivalent to those analytically continued from $H^4$ and that transform space
rules based on these coordinates can be used more readily. A proof of the
analogue of Goldstone's theorem in anti-de Sitter space is given using a
generalized plane wave representation of the commutator of the current and the
scalar field. It is shown that the introduction of curvature in the space-time
shifts the momentum by an amount which is determined by the Riemann tensor to
first order, and it follows that there is a shift in both the momentum and mass
scale in anti-de Sitter space.
\\ ( http://xxx.adelaide.edu.au/abs/hep-th/9702070 , 31kb)
------------------------------------------------------------------------------
\\
Paper: gr-qc/9704074
From: Don Koks <dkoks@physics.adelaide.edu.au>
Date: Sun, 27 Apr 1997 13:18:00 +0930 (CST)
Title: Thermal Particle Creation in Cosmological Spacetimes: A Stochastic Approach
Authors: Don Koks, B. L. Hu, Andrew Matacz, Alpan Raval
Comments: 17 pages, revtex (aps, eqsecnum), submitted to PRD, April 1997
Report-no: UMDPP 96-116
Journal-ref: Phys.Rev. D56 (1997) 4905-4915
\\
The stochastic method based on the influence functional formalism introduced
in an earlier paper to treat particle creation in near-uniformly accelerated
detectors and collapsing masses is applied here to treat thermal and
near-thermal radiance in certain types of cosmological expansions. It is
indicated how the appearance of thermal radiance in different cosmological
spacetimes and in the two apparently distinct classes of black hole and
cosmological spacetimes can be understood under a unifying conceptual and
methodological framework.
\\ ( http://xxx.adelaide.edu.au/abs/gr-qc/9704074 , 31kb)
------------------------------------------------------------------------------
\\
Paper: gr-qc/9705079
From: Robert Bartnik <bartnik@stan.canberra.edu.au>
Date: Wed, 28 May 1997 17:40:18 MDT (20kb)
Title: Shear-free Null Quasi-Spherical Spacetimes
Authors: Robert Bartnik
Comments: 20 pages, revtex
Report-no: UNE-MSCS-96-128
\\
The residual gauge freedom within the null quasi-spherical coordinate
condition is studied, for spacetimes admitting an {\em expanding, shear-free}
null foliation. The freedom consists of a boost and rotation at each coordinate
sphere, corresponding to a specification of inertial frame at each sphere.
Explicit formulae involving arbitrary functions of two variables are obtained
for the accelerated Minkowski, Schwarzschild, and Robinson-Trautman spacetimes.
These examples will be useful as test metrics in numerical relativity.
\\ ( http://xxx.adelaide.edu.au/abs/gr-qc/9705079 , 20kb)
------------------------------------------------------------------------------
\\
Paper: hep-ph/9707324
From: R.A.W.Gregory@durham.ac.uk (Ruth A W Gregory)
Date: Fri, 11 Jul 1997 14:40:19 +0100 (55kb)
Title: Effective action and motion of a cosmic string
Authors: Malcolm Anderson, Filipe Bonjour, Ruth Gregory and John Stewart
Comments: 24 pages revtex, 12 figures
Report-no: DTP/97/5, DAMTP/R-97/27
\\
We examine the leading order corrections to the Nambu effective action for
the motion of a cosmic string, which appear at fourth order in the ratio of the
width to radius of curvature of the string. We determine the numerical
coefficients of these extrinsic curvature corrections, and derive the equations
of motion of the worldsheet. Using these equations, we calculate the
corrections to the motion of a collapsing loop, a travelling wave, and a
helical breather. From the numerical coefficients we have calculated, we
discuss whether the string motion can be labelled as `rigid' or `antirigid,'
and hence whether cusp or kink formation might be suppressed or enhanced.
\\ ( http://xxx.adelaide.edu.au/abs/hep-ph/9707324 , 55kb)
------------------------------------------------------------------------------
\\
Paper: gr-qc/9708013
From: "" <phrtc@flinders.edu.au>
Date: Thu, 07 Aug 97 10:45:47 +0930
Title: Bootstrap Universe from Self-Referential Noise
Authors: Reginald T. Cahill, Christopher M. Klinger (Flinders University)
Comments: 10 pages, Latex
\\
We further deconstruct Heraclitean Quantum Systems giving a model for a
universe using pregeometric notions in which the end-game problem is overcome
by means of self-referential noise. The model displays self-organisation with
the emergence of 3-space and time. The time phenomenon is richer than the
present geometric modelling.
\\ ( http://xxx.adelaide.edu.au/abs/gr-qc/9708013 , 10kb)
------------------------------------------------------------------------------
\\
Paper: gr-qc/9708039
From: Leo Brewin <leo@newton.maths.monash.edu.au>
Date: Tue, 19 Aug 1997 02:58:16 MDT
Title: An ADM 3+1 formulation for Smooth Lattice General Relativity
Authors: Leo Brewin
Comments: 18 pages, plain TeX, 5 epsf figues, gzipped ps file also available
at this http URL
A new hybrid scheme for numerical relativity will be presented. The scheme will
employ a 3-dimensional spacelike lattice to record the 3-metric while using the
standard 3+1 ADM equations to evolve the lattice. Each time step will involve
three basic steps. First, the coordinate quantities such as the Riemann and
extrinsic curvatures are extracted from the lattice. Second, the 3+1 ADM
equations are used to evolve the coordinate data, and finally, the coordinate
data is used to update the scalar data on the lattice (such as the leg
lengths). The scheme will be presented only for the case of vacuum spacetime
though there is no reason why it could not be extended to non-vacuum
spacetimes. The scheme allows any choice for the lapse function and shift
vectors. An example for the Kasner $T^3$ cosmology will be presented and it
will be shown that the method has, for this simple example, zero discretisation
error.
\\ ( http://xxx.adelaide.edu.au/abs/gr-qc/9708039 , 38kb)
------------------------------------------------------------------------------
ALL SPACE IS NOT EQUAL:
PHYSICISTS FIND AXIS THAT GIVES THE UNIVERSE ORIENTATION
Physicists at the University of Rochester and the University of Kansas have
found evidence that flies in the face of the long-held belief that space is the
same in all directions (isotropic). In fact, measurements indicate something
seldom considered by physicists: that the universe has an orientation. The
unexpected finding, determined by measuring the polarization of light as it
travels to Earth from the far reaches of the universe, is the subject of a
paper in the April 21 issue of Physical Review Letters [Phys Rev Lett 78 (1997)
3043].
The work, which may be one of the most fundamental findings about the universe
in recent years, could affect physicists' views about the birth of the universe
and suggests that scientists will need to explore how Einstein's theory of
relativity and the theory of electromagnetism might explain the finding. That's
quite an impact from an effect so tiny that it's betrayed only by light
traveling across most of the observable universe, from 15 billion years ago.
Physicists have dubbed the effect the "corkscrew effect" for the way it twists
light crossing the heavens.
"The big news is that perhaps not all space is equal, for as far back as we can
peer in time," says Borge Nodland of the University of Rochester.
Adds co-investigator John Ralston of the University of Kansas: "The shocking
thing about our result is that there seems to be an absolute axis, a kind of
cosmological north star that orients the universe. We don't really know yet
what this axis represents."
This axis of orientation is not a physical entity but rather defines a
direction of space that somehow determines how light travels through the
universe. In effect, Ralston and Nodland have discovered a direction in space
that is out of the ordinary or different from all other directions. The idea
that any direction of space is in any way "special" has long been taboo among
astrophysicists.
"This work defies the notion that there is no 'up' or 'down' in space," says
Nodland, research fellow at Rochester's Theory Center for Optical Science and
Engineering.
From Earth, the axis of this orientation runs toward the constellation Sextans,
roughly in the direction of Leo and Gemini and high in the southern evening sky
this time of year. The other end of the axis points toward the constellations
Aquila and Equuleus. (Stargazers, of course, will see nothing special when they
look in that direction.) Nodland and Ralston, a professor of physics and
astronomy at Kansas, say the axis might have several interpretations: It could
be an intrinsic property of the universe, or it might indicate that an
undiscovered particle, such as the long- theorized axion, is at work.
The team made the finding by studying the polarization (orientation of electric
fields) of radio waves from 160 distant galaxies as measured in previous
experiments by astronomers around the world. Nodland and Ralston found that the
plane of polarization of the light rotates like a corkscrew as the light
travels through space, and that the orientation of the universal axis that
they've discovered is key to the amount of rotation. The rotation of
polarization depends on the angle at which the light moves relative to the axis
and on the distance the light travels before being measured. The effect is
crudely analogous to that of a crystal that twists light depending on the
direction light is traveling through the crystal.
Astronomers have long known about a somewhat similar effect called the Faraday
effect, which is caused by magnetic fields between galaxies and causes the
plane of polarization of light to rotate as the light travels through space.
The newly discovered effect is in addition to the Faraday effect.
Though the cause of the corkscrew effect remains unknown, in their paper the
team constructs a mathematical theory that explains the observations. The data
indicate that light actually travels through space at two slightly different
speeds. Such a mismatch in speeds would cause the polarization plane to rotate
in a well known manner, in a way that physics students see when they pass light
through corn syrup and look at the light with polarizing filters. This
corkscrew effect is far more subtle, though: Light traveling across the heavens
undergoes one full rotation of its plane of polarization about once in a
billion years.
Whatever the cause, the work could have widespread implications. Scientists
have long theorized that the Big Bang was completely symmetric. Says Nodland:
"Perhaps it was not a perfect Big Bang, but a Big Bang with a twist to space
and time." Such a twist would be seen today as a ripple of non-uniformity,
perhaps as the axis (an "axis of anisotropy") represents.
Much more speculatively, the work may provide some of the first experimental
evidence for physicists who have theorized the existence of other universes. If
our universe was asymmetric at creation, and symmetry in the cosmos is
maintained as many physicists believe, it raises the possibility of the
simultaneous creation of another universe with an opposite twist.
The work also seems to run counter to the notions that all space is uniform and
that the speed of light in a vacuum is always precisely the same, key
assumptions of the theory of special relativity.
Though the researchers say there's only a few chances in a thousand that the
result comes from statistical fluctuations, they stress the need for other
scientists to confirm their results.
Questions about the universe and our role in it have fascinated Nodland ever
since he can remember, filling his mind as he took long hikes while growing up
in his native Norway.
"I've always had a passionate interest in the universe and its origins," he
says. "We're on a little planet going around some burning mass that we call a
sun, in a certain region of space. What is this space, and why are we here? The
universe is amazing, and I want to know the most I can about it."
The team's work is funded by the U.S. Department of Energy, the National
Science Foundation, the New York State Energy Research and Development
Authority, and the Kansas Science and Technology Advanced Research (KSTAR)
program.