106 research outputs found
Effective Geometry
We introduce the concept of effective geometry by studying several systems in
which it arises naturally. As an example of the power and conciseness of the
method, it is shown that a flowing dielectric medium with a linear response to
an external electric field can be used to generate an analog geometry that has
many of the formal properties of a \Sch black hole for light rays, in spite of
birefringence. The surface gravity of this analog black hole has a contribution
that depends only on the dielectric properties of the fluid (in addition to the
usual term dependent on the acceleration). This term may be give a hint to a
new mechanism to increase the temperature of Hawking radiation.Comment: 13 pages, RevTex4, Contribution to the Proceedings of the Xth
Brazilian School of Gravitation and Cosmology, to be published by AI
Evolution of Vacuum Bubbles Embeded in Inhomogeneous Spacetimes
We study the propagation of bubbles of new vacuum in a radially inhomogeneous
background filled with dust or radiation, and including a cosmological
constant, as a first step in the analysis of the influence of inhomogeneities
in the evolution of an inflating region. We also compare the cases with dust
and radiation backgrounds and show that the evolution of the bubble in
radiation environments is notably different from that in the corresponding dust
cases, both for homogeneous and inhomogeneous ambients, leading to appreciable
differences in the evolution of the proper radius of the bubble.Comment: 18 pages, 15 figures, accepted for publication in Journal of
Cosmology and Astroparticle Physics (new version with a few cosmetic changes
w.r.t. the published one
Quantum relaxation in a system of harmonic oscillators with time-dependent coupling
In the context of the de Broglie-Bohm pilot wave theory, numerical
simulations for simple systems have shown that states that are initially out of
quantum equilibrium - thus violating the Born rule - usually relax over time to
the expected distribution on a coarse-grained level. We analyze the
relaxation of nonequilibrium initial distributions for a system of coupled
one-dimensional harmonic oscillators in which the coupling depends explicitly
on time through numerical simulations, focusing in the influence of different
parameters such as the number of modes, the coarse-graining length and the
coupling constant. We show that in general the system studied here tends to
equilibrium, but the relaxation can be retarded depending on the values of the
parameters, particularly to the one related to the strength of the interaction.
Possible implications on the detection of relic nonequilibrium systems are
discussed.Comment: 16 pages, 7 figure
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