1,342 research outputs found
Brane-world cosmology and varying
We consider a brane-world cosmological model coupled to a bulk scalar field.
Since the brane tension turns out to be proportional to Newton coupling , in
such a model a time variation of naturally occurs. By resorting to
available bounds on the variation of , the parameters of the model are
constrained. The constraints coming from nucleosynthesis and CMB result to be
the severest ones.Comment: 26 pages, 3 figure
Scalar Resonances in Axially Symmetric Spacetimes
We study properties of resonant solutions to the scalar wave equation in
several axially symmetric spacetimes. We prove that non-axial resonant modes do
not exist neither in the Lanczos dust cylinder, the extreme BTZ
spacetime nor in a class of simple rotating wormhole solutions. Moreover, we
find unstable solutions to the wave equation in the Lanczos dust cylinder and
in the region of the extreme BTZ spacetime, two solutions that
possess closed timelike curves. Similarities with previous results obtained for
the Kerr spacetime are explored.Comment: International Journal of Modern Physics D, in pres
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