18,788 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
The Corporate Securities Division of the State Gaming Control Board: An Overview and Guide to the Regulatory Process
Interface-induced magnetism in perovskite quantum wells
We investigate the angular dependence of the magnetoresistance of thin (< 1
nm), metallic SrTiO3 quantum wells epitaxially embedded in insulating,
ferrimagnetic GdTiO3 and insulating, antiferromagnetic SmTiO3, respectively.
The SrTiO3 quantum wells contain a high density of mobile electrons (~7x10^14
cm^-2). We show that the longitudinal and transverse magnetoresistance in the
structures with GdTiO3 are consistent with anisotropic magnetoresistance, and
thus indicative of induced ferromagnetism in the SrTiO3, rather than a
nonequilibrium proximity effect. Comparison with the structures with
antiferromagnetic SmTiO3 shows that the properties of thin SrTiO3 quantum wells
can be tuned to obtain magnetic states that do not exist in the bulk material.Comment: Accepted for publication as a Rapid Communication in Physical Review
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