188 research outputs found
Cosmological Einstein-Yang-Mills equations
We use a systematic construction method for invariant connections on
homogeneous spaces to find the Einstein-SU(n)-Yang-Mills equations for
Friedmann-Robertson-Walker and locally rotationally symmetric homogeneous
cosmologies. These connections depend on the choice of a homomorphism from the
isotropy group into the gauge group. We consider here the cases of the gauge
group SU(n) and SO(n) where these homomorphisms correspond to unitary or
orthogonal representations of the isotropy group. For some of the simpler cases
the full system of the evolution equations are derived, for others we only
determine the number of dynamical variables that remain after some mild fixing
of the gauge.Comment: 28 pages, uses amsmath,amsthm,amssymb,epsfig,verbatim, minor
correction
Axially Symmetric Bianchi I Yang-Mills Cosmology as a Dynamical System
We construct the most general form of axially symmetric SU(2)-Yang-Mills
fields in Bianchi cosmologies. The dynamical evolution of axially symmetric YM
fields in Bianchi I model is compared with the dynamical evolution of the
electromagnetic field in Bianchi I and the fully isotropic YM field in
Friedmann-Robertson-Walker cosmologies. The stochastic properties of axially
symmetric Bianchi I-Einstein-Yang-Mills systems are compared with those of
axially symmetric YM fields in flat space. After numerical computation of
Liapunov exponents in synchronous (cosmological) time, it is shown that the
Bianchi I-EYM system has milder stochastic properties than the corresponding
flat YM system. The Liapunov exponent is non-vanishing in conformal time.Comment: 18 pages, 6 Postscript figures, uses amsmath,amssymb,epsfig,verbatim,
to appear in CQ
Hamilton-Jacobi Solutions for Strongly-Coupled Gravity and Matter
A Green's function method is developed for solving strongly-coupled gravity
and matter in the semiclassical limit. In the strong-coupling limit, one
assumes that Newton's constant approaches infinity. As a result, one may
neglect second order spatial gradients, and each spatial point evolves like an
homogeneous universe. After constructing the Green's function solution to the
Hamiltonian constraint, the momentum constraint is solved using functional
methods in conjunction with the superposition principle for Hamilton-Jacobi
theory. Exact and approximate solutions are given for a dust field or a scalar
field interacting with gravity.Comment: 26 pages Latex (IOP) file with 2 IOP style files, to be published in
Classical and Quantum Gravity (1998
Stabilization of the Yang-Mills chaos in non-Abelian Born-Infeld theory
We investigate dynamics of the homogeneous time-dependent SU(2) Yang-Mills
fields governed by the non-Abelian Born-Infeld lagrangian which arises in
superstring theory as a result of summation of all orders in the string slope
parameter . It is shown that generically the Born-Infeld dynamics is
less chaotic than that in the ordinary Yang-Mills theory, and at high enough
field strength the Yang-Mills chaos is stabilized. More generally, a smothering
effect of the string non-locality on behavior of classical fields is
conjectured.Comment: 7 pages, 5 figure
Anisotropic Inflation with Non-Abelian Gauge Kinetic Function
We study an anisotropic inflation model with a gauge kinetic function for a
non-abelian gauge field. We find that, in contrast to abelian models, the
anisotropy can be either a prolate or an oblate type, which could lead to a
different prediction from abelian models for the statistical anisotropy in the
power spectrum of cosmological fluctuations. During a reheating phase, we find
chaotic behaviour of the non-abelian gauge field which is caused by the
nonlinear self-coupling of the gauge field. We compute a Lyapunov exponent of
the chaos which turns out to be uncorrelated with the anisotropy.Comment: 16 pages, 4 figure
Chaos in the Einstein-Yang-Mills Equations
Yang-Mills color fields evolve chaotically in an anisotropically expanding
universe. The chaotic behaviour differs from that found in anisotropic
Mixmaster universes. The universe isotropizes at late times, approaching the
mean expansion rate of a radiation-dominated universe. However, small chaotic
oscillations of the shear and color stresses continue indefinitely. An
invariant, coordinate-independent characterisation of the chaos is provided by
means of fractal basin boundaries.Comment: 3 pages LaTeX + 3 pages of figure
The Politics of Commerce : The Congress of Chambers of Commerce of the Empire, 1886-1914
Peer reviewedPublisher PD
Memory and meaning in the search for Chinese Australian families
Over the past twenty-five years there has been tremendous interest in researching ChineseAustralian family history. This includes documenting the experiences of Chinese migrantsand their descendants in Australia from the nineteenth century onwards, as well as seekingto understand their pre-migration lives in China and patterns of return migration. For manyChinese Australian family historians, however, there remains a major difficulty in tracingtheir Chinese ancestry â not knowing their ancestorâs name in Chinese or their precise placeof origin beyond the ubiquitous âCantonâ. This essay discusses the endeavours of familyhistorians to uncover their Cantonese roots, including by visiting the qiaoxiang (homevillage) districts of the Pearl River Delta region in Guangdong province. We reflect on thisâroots tourismâ and the practice of personal memory-making in the wake of national andfamilial forgetting
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