33 research outputs found
Stationary vs. singular points in an accelerating FRW cosmology derived from six-dimensional Einstein-Gauss-Bonnet gravity
Six-dimensional Einstein-Gauss-Bonnet gravity (with a linear Gauss-Bonnet
term) is investigated. This theory is inspired by basic features of results
coming from string and M-theory. Dynamical compactification is carried out and
it is seen that a four-dimensional accelerating FRW universe is recovered, when
the two-dimensional internal space radius shrinks. A non-perturbative structure
of the corresponding theory is identified which has either three or one stable
fixed points, depending on the Gauss-Bonnet coupling being positive or
negative. A much richer structure than in the case of the perturbative regime
of the dynamical compactification recently studied by Andrew, Bolen, and
Middleton is exhibited.Comment: 9 pages, 20 figures, accepted in PL
Dynamical Casimir Effect and Quantum Cosmology
We apply the background field method and the effective action formalism to
describe the four-dimensional dynamical Casimir effect. Our picture corresponds
to the consideration of quantum cosmology for an expanding FRW universe (the
boundary conditions act as a moving mirror) filled by a quantum massless GUT
which is conformally invariant. We consider cases in which the static Casimir
energy is repulsive and attractive. Inserting the simplest possible inertial
term, we find, in the adiabatic (and semiclassical) approximation, the
dynamical evolution of the scale factor and the dynamical Casimir stress
analytically and numerically (for SU(2) super Yang-Mills theory). Alternative
kinetic energy terms are explored in the Appendix.Comment: 14 pages, REVTeX 4, 6 eps figure
(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