Superinflation, quintessence, and nonsingular cosmologies

Abstract

The dynamics of a universe dominated by a self-interacting nonminimally coupled scalar field are considered. The structure of the phase space and complete phase portraits are given. New dynamical behaviors include superinflation ($\dot{H}>0$), avoidance of big bang singularities through classical birth of the universe, and spontaneous entry into and exit from inflation. This model is promising for describing quintessence as a nonminimally coupled scalar field.Comment: 4 pages, 2 figure

Singularities of gravity in the presence of nonminimally coupled scalar fields

“…This is the case, for instance, of some solutions exhibiting superinflation regimes. The heteroclinic and homoclinic solutions identified in [1,2] can cross the F (φ) = 0 hypersurface and, hence, they also suffer the same instability against anisotropic perturbations. The homoclinic solutions were considered as candidates to describe a non-singular cosmological history, with the big-bang singularity being avoided through a classical birth of the universe from empty Minkowski space.…”

“…(17) and (18), any deviation from perfect isotropy (expressed by nonvanishing q and r variables) for these solutions, however small, will lead catastrophically to a geometrical singularity. Many of the novel dynamical behaviors presented in [1,2] depend on these solutions. This is the case, for instance, of some solutions exhibiting superinflation regimes.…”

“…Recently [1,2], we have investigated the dynamics of homogeneous and isotropic solutions of the cosmological model described by the action:…”

de Sitter attractors in generalized gravity

“…It has been suggested that the present universe could have originated from Minkowski space [30,31] or from a static Einstein space [33,28]. To pursue this idea it is necessary to ascertain the stability of Minkowski or Einstein space.…”

Energy conditions and classical scalar fields

“…(2.13) in the effective coupling approach. For example, solutions in which φ is constant and equal to the critical values (2.16) appear in models of wormholes [22] and as special heteroclinics in the phase space of scalar field cosmology [31] (see the Appendix for a discussion of solutions with constant scalar field). In the effective coupling approach these solutions, which are important ones for wormholes and cosmology, are missed and can only be recovered by going back to the primitive form (2.1) of the field equations.…”