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Vacuum polarization by topological defects in de Sitter spacetime
In this paper we investigate the vacuum polarization effects associated with
a massive quantum scalar field in de Sitter spacetime in the presence of
gravitational topological defects. Specifically we calculate the vacuum
expectation value of the field square, . Because this investigation
has been developed in a pure de Sitter space, here we are mainly interested on
the effects induced by the presence of the defects.Comment: Talk presented at the 1st. Mediterranean Conference on Classical and
Quantum Gravity (MCCQG
On Effective Spacetime Dimension in the Ho\v{r}ava-Lifshitz Gravity
In this manuscript we explicitly compute the effective dimension of spacetime
in some backgrounds of Ho\v{r}ava-Lifshitz (H-L) gravity. For all the cases
considered, the results are compatible with a dimensional reduction of the
spacetime to , at high energies (ultraviolet limit), which is confirmed
by other quantum gravity approaches, as well as to , at low energies
(infrared limit). This is obtained by computing the free energy of massless
scalar and gauge fields. We find that the only effect of the background is to
change the proportionality constant between the internal energy and
temperature. Firstly, we consider both the non-perturbative and perturbative
models involving the matter action, without gravitational sources but with
manifest time and space symmetry breaking, in order to calculate modifications
in the Stephan-Boltzmann law. When gravity is taken into account, we assume a
scenario in which there is a spherical source with mass and radius in
thermal equilibrium with radiation, and consider the static and spherically
symmetric solution of the H-L theory found by Kehagias-Sfetsos (K-S), in the
weak and strong field approximations. As byproducts, for the weak field regime,
we used the current uncertainty of the solar radiance measurements to establish
a constraint on the free parameter of the K-S solution. We also
calculate the corrections, due to gravity, to the recently predicted attractive
force that black bodies exert on nearby neutral atoms and molecules.Comment: references adde
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