We review the general features of nonsingular universes (ie those that go from an era of
accelerated collapse to an expanding era without displaying a singularity) as well as cyclic …

Beyond Einstein's Gravity is a graduate level introduction to extended theories of gravity and
cosmology, including variational principles, the weak-field limit, gravitational waves …

Nature's simplest field, the scalar field, has been the protagonist of physical theories for a
long time. Even before the publication of the theory of general relativity G. Nordström …

Using the low limit of cosmic ages from globular cluster and the white dwarfs: t0> 12Gyr,
together with recent new high redshift supernova observations from the HST/GOODS …

We consider a late-time cosmological model based on a recent proposal that the infinite-
bare-coupling limit of superstring or M theory exists and has good phenomenological …

The different definitions for the equation of state of a nonminimally coupled scalar field that
have been introduced in the literature are analyzed. Particular emphasis is made upon …

Conditions for the existence and stability of de Sitter space in modified gravity are derived by
considering inhomogeneous perturbations in a gauge-invariant formalism. The stability …

There is marginal evidence that the quintessential form of matter responsible for the
acceleration of the universe observed today has ratio between pressure and energy density …

In this Letter we will investigate the validity of the generalized second law of
thermodynamics for the quintom model of dark energy. Reviewing briefly the quintom …

We investigate quintom cosmology in FRW universes using isomorphic models consisting of
three coupled oscillators, one of which carries negative kinetic energy. In particular, we …