Israel Quiros

Quintom cosmologies with arbitrary potentials

In this Letter we investigate quintom cosmologies with arbitrary potentials from the dynamical systems perspective. The dynamical systems analysis is complete in the sense that it includes the asymptotic regime where both scalar fields diverge, which proves to be particularly relevant in connection with the existence of tracking phases. The results of the present study indicate that the existence of phantom attractors is not generic: for quintom models there may exist either de Sitter attractors associated with the saddle points of the potential, or tracking attractors in the asymptotic regime where the scalar fields diverge.

Crossing the phantom divide without phantom matter

A class of braneworld models can lead to phantom-like acceleration of the late universe, but without the need for any phantom matter. In the simplest models, the universe contains only cold dark matter and a cosmological constant. We generalize these models by introducing a quintessence field. The new feature in our models is that quintessence leads to a crossing of the phantom divide, w = −1. This is a purely gravitational effect, and there is no phantom instability. Furthermore, the Hubble parameter is always decreasing, and there is no big rip singularity in the future.

Self-interacting scalar field trapped in a Randall-Sundrum braneworld: The dynamical systems perspective

Abstract We apply the dynamical systems tools to study the linear dynamics of a self-interacting scalar field trapped on a Randall–Sundrum brane. The simplest kinds of self-interaction potentials are investigated: (a) constant potential, and (b) exponential potential. It is shown that the dynamics of the Randall–Sundrum model significantly differs from the standard four-dimensional behavior at early times: in all cases of interest the (singular) empty universe is the past attractor for every trajectory in phase space, meanwhile the kinetic energy-dominated solution is always a saddle critical point. The late-time dynamics is not affected by the brane effects.

Brans-Dicke cosmology does not have theCDM phase as an universal attractor

In this paper we seek for relevant information on the asymptotic cosmological dynamics of the Brans--Dicke theory of gravity for several self-interaction potentials. By means of the simplest tools of the dynamical systems theory, it is shown that the general relativity de Sitter solution is an attractor of the Jordan frame (dilatonic) Brans--Dicke theory only for the exponential potential

Chameleon effect in the Jordan frame of the Brans-Dicke theory

U(\vphi)\propto\exp\vphi

Dynamical systems analysis of the cubic galileon beyond the exponential potential and the cosmological analogue of the vDVZ discontinuity

, which corresponds to the quadratic potential

Mass hierarchy and mass gap on thick branes with Poincare symmetry

V(\phi)\propto\phi^2

Scale invariant theory of gravity and the standard model of particles

in terms of the original Brans--Dicke field

Scale invariance and broken electroweak symmetry may coexist together

\phi=\exp\vphi

Scale invariance: fake appearances

, or for potentials which asymptote to