39,761 research outputs found
Black string corrections in variable tension braneworld scenarios
Braneworld models with variable tension are investigated, and the corrections
on the black string horizon along the extra dimension are provided. Such
corrections are encrypted in additional terms involving the covariant
derivatives of the variable tension on the brane, providing profound
consequences concerning the black string horizon variation along the extra
dimension, near the brane. The black string horizon behavior is shown to be
drastically modified by the terms corrected by the brane variable tension. In
particular, a model motivated by the phenomenological interesting case
regarding Eotvos branes is investigated. It forthwith provides further physical
features regarding variable tension braneworld scenarios, heretofore concealed
in all previous analysis in the literature. All precedent analysis considered
uniquely the expansion of the metric up to the second order along the extra
dimension, what is able to evince solely the brane variable tension absolute
value. Notwithstanding, the expansion terms aftermath, further accomplished in
this paper from the third order on, elicits the successive covariant
derivatives of the brane variable tension, and their respective coupling with
the extrinsic curvature, the Weyl tensor, and the Riemann and Ricci tensors, as
well as the scalar curvature. Such additional terms are shown to provide sudden
modifications in the black string horizon in a variable tension braneworld
scenarioComment: 12 pages, 5 figures, accepted in PR
Notes on the Two-brane Model with Variable Tension
Motivated by possible extensions of the braneworld models with two branes, we
investigate some consequences of a variable brane tension using the well
established results on consistency conditions. By a slight modification of the
usual stress-tensor used in order to derive the braneworld sum rules, we find
out some important constraints obeyed by time dependent brane tensions. In
particular it is shown that the tensions of two Randall-Sundrum like branes
obeying, at the same time, an Eotvos law, aggravate the fine tuning problem.
Also, it is shown that if the hidden brane tension obeys an Eotvos law, then
the visible brane has a mixed behavior allowing a bouncing-like period at early
times while it is dominated by an Eotvos law nowadays. To finalize, we discuss
some qualitative characteristics which may arise in the scope of dynamical
brane tensions, as anisotropic background and branons production.Comment: 7 pages, 1 figure, accepted for publication in Physical Review
Levantamento de plantas conhecidas como Mututi, com ênfase ao estudo morfológico de espécies de Pterocarpus Jarq. (Leguminosae).
Disponível também on-line
Effective lagrangian for a mass dimension one fermionic field in curved spacetime
In this work we use momentum-space techniques to evaluate the propagator
for a spin mass dimension one spinor field on a curved
Friedmann-Robertson-Walker spacetime. As a consequence, we built the one-loop
correction to the effective lagrangian in the coincidence limit. Going further
we compute the effective lagrangian in the finite temperature regime. We arrive
at interesting cosmological consequences, as time-dependent cosmological
`constant', fully explaining the functional form of previous cosmological
models.Comment: 9 pages, 0 figure
Levantamento de plantas conhecidas como Mututi, com ênfase ao estudo morfológico de espécies de Pterocarpus Jacq. (Leguminosae).
Disponível também on-line
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