Thawing Dark Energy Models with nearly Flat Potentials
by
Anjan Sen
→
Europe/Berlin
Description
The thawing quintessence model with a nearly flat potential provides a
natural mechanism to produce an equation of state parameter, w, close to -1
today. We examine the behavior of such models for the case in which the
potential satisfies the slow roll conditions: [(1/V)(dV/dphi)]^2 << 1 and
(1/V)(d^2 V/dphi^2) << 1, and we derive the analog of the slow-roll
approximation for the case in which both matter and a scalar field
contribute to the density. We consider both ordinary scalar fields as well
as fields having DBI type kinetic energy. We show that in this limit, all
such models converge to a unique relation between 1+w, Omega_phi, and the
initial value of (1/V)(dV/dphi). We derive this relation, and use it to
determine the corresponding expression for w(a), which depends only on the
present-day values for w and Omega_phi. Later on, we relax the slow-roll
approximation and study in a general way the cosmological evolution with
thawing scalar fields. We also put constraint on the background cosmology
using various observational data.