8 research outputs found
Cylindrical solutions in braneworld gravity
In this article we investigate exact cylindrically symmetric solutions to the
modified Einstein field equations in the brane world gravity scenarios. It is
shown that for the special choice of the equation of state for the
dark energy and dark pressure, the solutions found could be considered formally
as solutions of the Einstein-Maxwell equations in 4-D general relativity.Comment: 12 pages, RevTex format, typos corrected and references added.
Accepted for publication in PR
Complexity Growth Following Multiple Shocks
In this paper by making use of the "Complexity=Action" proposal, we study the
complexity growth after shock waves in holographic field theories. We consider
both double black hole-Vaidya and AdS-Vaidya with multiple shocks geometries.
We find that the Lloyd's bound is respected during the thermalization process
in each of these geometries and at the late time, the complexity growth
saturates to the value which is proportional to the energy of the final state.
We conclude that the saturation value of complexity growth rate is independent
of the initial temperature and in the case of thermal initial state, the rate
of complexity is always less than the value for the vacuum initial state such
that considering multiple shocks it gets more smaller. Our results indicate
that by increasing the temperature of the initial state, the corresponding rate
of complexity growth starts far from final saturation rate value.Comment: 19 pages, 3 figs, Ref.s adde
Quantum gravitational optics in the field of a gravitomagnetic monopole
Vacuum polarization in QED in a background gravitational field induces
interactions which {\it effectively} modify the classical picture of light rays
as the null geodesics of spacetime. After a short introduction on the main
aspects of the quantum gravitational optics, as a nontrivial example, we study
this effect in the background of NUT space characterizing the spacetime of a
spherical mass endowed with a gravitomagnetic monopole charge, the so called
NUT factor.Comment: 9 pages, title changed and the text abridged for publication in the
Journal of Physics: Conference serie
Fermat's principle in quantum gravitational optics
Interactions incorporating the vacuum polarization effects in curved
backgrounds modify the null cone structure in such a way that the photon
trajectories would not be the space-time geodesics anymore. The gravitational
birefringence introduced as a direct consequence of these effects, will allow
shifts in the photon velocities leading to polarization dependent superluminal
propagation. Taking these effects into account we study Fermat's principle in
the context of the 1+3 (threading) formulation of the space-time decomposition.
We find an expression for the modified spacetime refractive index and show it
is proportional to the light cone correction to the first order. Consequences
of this modification on polarization sum rules and spatial light paths are
considered.Comment: 13 Pages, REVTex format, section on gravitomagnetic monopoles is
removed along with its references, new references adde
Fields Annihilation and Particles Creation in DBI inflation
We consider a model of DBI inflation where two stacks of mobile branes are
moving ultra relativistically in a warped throat. The stack closer to the tip
of the throat is annihilated with the background anti-branes while inflation
proceeds by the second stack. The effects of branes annihilation and particles
creation during DBI inflation on the curvature perturbations power spectrum and
the scalar spectral index are studied. We show that for super-horizon scales,
modes which are outside the sound horizon at the time of branes collision, the
spectral index has a shift to blue spectrum compared to the standard DBI
inflation. For small scales the power spectrum approaches to its background DBI
inflation value with the decaying superimposed oscillatory modulations.Comment: First revision: minor changes, the background spectral index is
corrected, new references are added. Second revision: minor changes, new
references are added, accepted for publication in JCA