13,266 research outputs found
Variable Speed of Light Cosmology and Bimetric Gravity: An Alternative to Standard Inflation
A scalar-tensor bimetric gravity model of early universe cosmology is
reviewed. The metric frame with a variable speed of light (VSL) and a constant
speed of gravitational waves is used to describe a Friedmann-Robertson-Walker
universe. The Friedmann equations are solved for a radiation dominated equation
of state and the power spectrum is predicted to be scale invariant with a
scalar mode spectral index . The scalar modes are born in a ground
state superhorizon and the fluctuation modes are causally connected by the VSL
mechanism. The cosmological constant is equated to zero and there is no
significant dependence on the scalar field potential energy. A possible way of
distinguishing the metric gravity model from standard inflationary models is
discussed.Comment: 10 pages. Latex file. No figures. Talk given at the Coral Gables
Conference on High Energy Physics and Cosmology, Fort Lauderdale, Florida,
December 17-21, 2003. Typos corrected. Reference adde
Massive NGT and Spherically Symmetric Systems
The arguments leading to the introduction of the massive Nonsymmetric
Gravitational action are reviewed \cite{Moffat:1994,Moffat:1995b}, leading to
an action that gives asymptotically well-behaved perturbations on GR
backgrounds. Through the analysis of spherically symmetric perturbations about
GR (Schwarzschild) and NGT (Wyman-type) static backgrounds, it is shown that
spherically symmetric systems are not guaranteed to be static, and hence
Birkhoff's theorem is not valid in NGT. This implies that in general one must
consider time dependent exteriors when looking at spherically symmetric systems
in NGT. For the surviving monopole mode considered here there is no energy flux
as it is short ranged by construction. Further work on the spherically
symmetric case will be motivated through a discussion of the possibility that
there remain additional modes that do not show up in weak field situations, but
nonetheless exist in the full theory and may again result in bad global
asymptotics. A presentation of the action and field equations in a general
frame is given in the course of the paper, providing an alternative approach to
dealing with the algebraic complications inherent in NGT, as well as offering a
more general framework for discussing the physics of the antisymmetric sector.Comment: `Final' version (minor changes have been made to the original), to be
published in J. Math. Phys. Typset using ReVTeX and amssymbols. 29 page
Issues in Quantum-Geometric Propagation
A discussion of relativistic quantum-geometric mechanics on phase space and
its generalisation to the propagation of free, massive, quantum-geometric
scalar fields on curved spacetimes is given. It is shown that in an arbitrary
coordinate system and frame of reference in a flat spacetime, the resulting
propagator is necessarily the same as derived in the standard Minkowski
coordinates up to a Lorentz boost acting on the momentum content of the field,
which is therefore seen to play the role of Bogolubov transformations in this
formalism. These results are explicitly demonstrated in the context of a Milne
universe.Comment: 19 pages; requires amsart, amssymb, amsmat
Canonical general relativity: Matter fields in a general linear frame
Building on the results of previous work, we demonstrate how matter fields
are incorporated into the general linear frame approach to general relativity.
When considering the Maxwell one-form field, we find that the system that leads
naturally to canonical vierbein general relativity has the extrinsic curvature
of the Cauchy surface represented by gravitational as well as non-gravitational
degrees of freedom. Nevertheless the metric compatibility conditions are
undisturbed, and this apparent derivative-coupling is seen to be an effect of
working with (possibly orthonormal) linear frames. The formalism is adapted to
consider a Dirac Fermion, where we find that a milder form of this apparent
derivative-coupling appears.Comment: 13 pages; uses AMS-latex style file
The Initial-Value Problem of Spherically Symmetric Wyman Sector Nonsymmetric Gravitational Theory
We cast the four-dimensional field equations of the Nonsymmetric
Gravitational Theory (NGT) into a form appropriate for numerical study. In
doing so, we have restricted ourselves to spherically symmetric spacetimes, and
we have kept only the Wyman sector of the theory. We investigate the
well-posedness of the initial-value problem of NGT for a particular data set
consisting of a pulse in the antisymmetric field on an asymptotically flat
space background. We include some analytic results on the solvability of the
initial-value problem which allow us to place limits on the regions of the
parameter space where the initial-value problem is solvable. These results are
confirmed by numerically solving the constraints.Comment: REVTeX 3.0 with epsf macros and AMS symbols, 18 pages, 9 figure
Abelian Anomalies in Nonlocal Regularization
Nonlocal regularization of QED is shown to possess an axial anomaly of the
same form as other regularization schemes. The Noether current is explicitly
constructed and the symmetries are shown to be violated, whereas the identities
constructed when one properly considers the contribution from the path integral
measure are respected. We also discuss the barrier to quantizing the fully
gauged chiral invariant theory, and consequences.Comment: 21 pages, UTPT-93-0
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