73 research outputs found
Finite action, holographic conformal anomaly and quantum brane-worlds in d5 gauged supergravity
We report our recent results concerning d5 gauged supergravity (dilatonic
gravity) considered on AdS background. The finite action on such background as
well as d4 holographic conformal anomaly (via AdS/CFT correspondence) are
found. In such formalism the bulk potential is kept to be arbitrary, dilaton
dependent function. Holographic RG in such theory is briefly discussed. d5 AdS
brane-world Universe induced by quantum effects of brane CFT is constructed.
Such brane is spherical, hyperbolic or flat one. Hence, the possibility of
quantum creation of inflationary brane-world Universe is shown.Comment: Proceedings of Londrina conference, April 2000, to appea
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
Quantum bounds for gravitational de Sitter entropy and the Cardy-Verlinde formula
We analyze different types of quantum corrections to the Cardy-Verlinde
entropy formula in a Friedmann-Robertson-Walker universe and in an (anti)-de
Sitter space. In all cases we show that quantum corrections can be represented
by an effective cosmological constant which is then used to redefine the
parameters entering the Cardy-Verlinde formula so that it becomes valid also
with quantum corrections, a fact that we interpret as a further indication of
its universality. A proposed relation between Cardy-Verlinde formula and the
ADM Hamiltonian constraint is given.Comment: LaTeX file, 15 pages, reference is adde
(Non) singular Kantowski-Sachs Universe from quantum spherically reduced matter
Using s-wave and large N approximation the one-loop effective action for 2d
dilaton coupled scalars and spinors which are obtained by spherical reduction
of 4d minimal matter is found. Quantum effective equations for reduced Einstein
gravity are written. Their analytical solutions corresponding to 4d
Kantowski-Sachs (KS) Universe are presented. For quantum-corrected Einstein
gravity we get non-singular KS cosmology which represents 1) quantum-corrected
KS cosmology which existed on classical level or 2)purely quantum solution
which had no classical limit. The analogy with Nariai BH is briefly mentioned.
For purely induced gravity (no Einstein term) we found general analytical
solution but all KS cosmologies under discussion are singular. The
corresponding equations of motion are reformulated as classical mechanics
problem of motion of unit mass particle in some potential V.Comment: LaTeX file, 16 pages, a few misprints are correcte
Induced wormholes due to quantum effects of spherically reduced matter in large N approximation
Using one-loop effective action in large N and s-wave approximation we
discuss the possibility to induce primordial wormholes at the early Universe.
An analytical solution is found for self-consistent primordial wormhole with
constant radius. Numerical study gives the wormhole solution with increasing
throat radius and increasing red-shift function. There is also some indication
to the possibility of a topological phase transition.Comment: LaTeX file, 2 eps figures, 9 pages, few misprints are corrected,
numerics are change
Supersymmetric new brane-world
The quantum-induced dilatonic brane world (New Brane World) is created by
brane CFT quantum effects (giving effective brane tension) in accordance with
AdS/CFT set-up which also defines surface term. Considering the bosonic sector
of 5d gauged supergravity with single scalar and taking the boundary action as
predicted by supersymmetry, the possibility to supersymmetrize dilatonic New
Brane World is discussed. It is demonstrated that for a number of
superpotentials the flat SUSY dilatonic brane-world (with dynamically induced
brane dilaton) or quantum-induced de Sitter dilatonic brane-world (not Anti-de
Sitter one) where SUSY is broken by the quantum effects occurs. The analysis of
graviton perturbations indicates that gravity is localized on such branes.Comment: LaTeX 16 pages, misprints are correcte
Cosmological anti-deSitter space-times and time-dependent AdS/CFT correspondence
We study classes of five-dimensional cosmological solutions with negative
curvature, which are obtained from static solutions by an exchange of a spatial
and temporal coordinate, and in some cases by an analytic continuation. Such
solutions provide a suitable laboratory to address the time-dependent AdS/CFT
correspondence. For a specific example we address in detail the calculation of
the boundary stress-energy and the Wilson line and find disagreement with the
standard AdS/CFT correspondence. We trace these discrepancies to the
time-dependent effects, such as particle creation, which we further study for
specific backgrounds. We also identify specific time-dependent backgrounds that
reproduce the correct conformal anomaly. For such backgrounds the calculation
of the Wilson line in the adiabatic approximation indicates only a Coulomb
repulsion.Comment: LaTeX file, 47 pages, discussion is extended, version to appear in
PR
Dynamics of Quintessence Models of Dark Energy with Exponential Coupling to the Dark Matter
We explore quintessence models of dark energy which exhibit non-minimal
coupling between the dark matter and the dark energy components of the cosmic
fluid. The kind of coupling chosen is inspired in scalar-tensor theories of
gravity. We impose a suitable dynamics of the expansion allowing to derive
exact Friedmann-Robertson-Walker solutions once the coupling function is given
as input. Self-interaction potentials of single and double exponential types
emerge as result of our choice of the coupling function. The stability and
existence of the solutions is discussed in some detail. Although, in general,
models with appropriated interaction between the components of the cosmic
mixture are useful to handle the coincidence problem, in the present study the
coincidence can not be evaded due to the choice of the solution generating
ansatz.Comment: 10 pages, 7 figure
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