449 research outputs found
Stability of de Sitter Solutions in Non-local Cosmological Models
A non-local gravity model, which includes a function , where
is the d'Alembert operator, is considered. For the model with an
exponential de Sitter solutions are explored, without any
restrictions on the parameters. Using Hubble-normalized variables, the
stability of the de Sitter solutions is investigated, with respect to
perturbations in the Bianchi I metric, in the case of zero cosmological
constant, and sufficient conditions for stability are obtained.Comment: 10 pages, has been published in the proceedings of the XXth
International Workshop on High Energy Physics and Quantum Field Theory
(QFTHEP'2011), http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=13
Calculation of Ground State Energy for Confined Fermion Fields
A method for renormalization of the Casimir energy of confined fermion fields
in (1+1)D is proposed. It is based on the extraction of singularities which
appear as poles at the point of physical value of the regularization parameter,
and subsequent compensation of them by means of redefinition of the "bare"
constants. A finite ground state energy of the two-phase hybrid model of
fermion bag with chiral boson-fermion interaction is calculated as the function
of the bag's size.Comment: 10 pages, LaTeX; no figures. Version to appear in Phys. Lett. B
(2001
Unified approach to study quantum properties of primordial black holes, wormholes and of quantum cosmology
We review the anomaly induced effective action for dilaton coupled spinors
and scalars in large N and s-wave approximation. It may be applied to study the
following fundamental problems: construction of quantum corrected black holes
(BHs), inducing of primordial wormholes in the early Universe (this effect is
confirmed) and the solution of initial singularity problem. The recently
discovered anti-evaporation of multiple horizon BHs is discussed. The existance
of such primordial BHs may be interpreted as SUSY manifestation. Quantum
corrections to BHs thermodynamics maybe also discussed within such scheme.Comment: LaTeX file and two eps files, to appear in MPLA, Brief Review
Casimir effect in de Sitter and Anti-de Sitter braneworlds
We discuss the bulk Casimir effect (effective potential) for a conformal or
massive scalar when the bulk represents five-dimensional AdS or dS space with
two or one four-dimensional dS brane, which may correspond to our universe.
Using zeta-regularization, the interesting conclusion is reached, that for both
bulks in the one-brane limit the effective potential corresponding to the
massive or to the conformal scalar is zero. The radion potential in the
presence of quantum corrections is found. It is demonstrated that both the dS
and the AdS braneworlds may be stabilized by using the Casimir force only. A
brief study indicates that bulk quantum effects are relevant for brane
cosmology, because they do deform the de Sitter brane. They may also provide a
natural mechanism yielding a decrease of the four-dimensional cosmological
constant on the physical brane of the two-brane configuration.Comment: 37 pages, LaTeX, references added, some revision is done, version to
appear in PR
Effective potential and stability of the rigid membrane
The calculation of the effective potential for fixed-end and toroidal rigid
-branes is performed in the one-loop as well as in the approximations.
The analysis of the involved zeta-functions (of inhomogeneous Epstein type)
which appear in the process of regularization is done in full detail.
Assymptotic formulas (allowing only for exponentially decreasing errors of
order ) are found which carry all the dependences on the basic
parameters of the theory explicitly. The behaviour of the effective potential
(specified to the membrane case ) is investigated, and the extrema of this
effective potential are obtained.Comment: 15 PAGE
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