56 research outputs found
Vacuumless kinks systems from vacuum ones, an example
Some years ago, Cho and Vilenkin, introduced a model which presents
topological solutions, despite not having degenerate vacua as is usually
expected. Here we present a new model with topological defects, connecting
degenerate vacua but which in a certain limit recovers precisely the one
proposed originally by Cho and Vilenkin. In other words, we found a kind of
parent model for the so called vacuumless model. Then the idea is extended to a
model recently introduced by Bazeia et al. Finally, we trace some comments the
case of the Liouville model.Comment: 11 pages, 4 figure
Variation of the speed of light with temperature of the expanding universe
From an extended relativistic dynamics for a particle moving in a cosmic
background field with temperature T, we aim to obtain the speed of light with
an explicit dependence on the background temperature of the universe. Although
finding the speed of light in the early universe much larger than its current
value, our approach does not violate the postulate of special relativity.
Moreover, it is shown that the high value of the speed of light in the early
universe was drastically decreased before the beginning of the inflationary
period. So we are led to conclude that the theory of varying speed of light
should be questioned as a possible solution of the horizon problem.Comment: 3 pages and 1 figure; Phys. Rev. D86, 027703 (2012
Degenerate and critical Bloch branes
In the last few years a number of works reported the appearance of thick
branes with internal structure, induced by the parameter which controls the
interaction between two scalar fields coupled to gravity in (4,1) dimensions in
warped space-time with one extra dimension. Here we show that one can implement
the control over the brane thickness without needing to change the potential
parameter. On the contrary, this is going to be done by means of the variation
of a parameter associated to the domain wall degeneracy. We also report the
existence of novel and qualitatively different solutions for a critical value
of the degeneracy parameter, which could be called critical Bloch branes.Comment: 7 figure
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