Cosmologists today are confronted with the perplexing reality that the universe is currently
accelerating in its expansion. Nevertheless, the nature of the fuel that drives today's cosmic …

A large number of recent observational data strongly suggest that we live in a flat,
accelerating Universe composed of~ 1/3 of matter (baryonic+ dark) and~ 2/3 of an exotic …

It has been suggested that a scalar field with negative kinetic energy, or “ghost,” could be the
source of the observed late-time cosmological acceleration. Naively, such theories should …

We study the general features of a dynamics of a phantom field in the cosmological context.
In the case of an inverse coshyperbolic potential, we demonstrate that the phantom field can …

We investigate a flat Friedmann-Robertson-Walker spacetime filled with k essence and find
the set of functions F that generate three different families of extended tachyon fields and …

In this paper we analyze the cosmological dynamics of phantom field in a variety of
potentials unbounded from above. We demonstrate that the nature of future evolution …

The kinematic approach to cosmological tests provides direct evidence to the present
accelerating stage of the Universe that does not depend on the validity of general relativity …

The transition redshift (deceleration/acceleration) is discussed by expanding the
deceleration parameter to first order around its present value. A detailed study is carried out …

Determining the mechanism behind the current cosmic acceleration constitutes a major
question nowadays in theoretical physics. If the dark energy route is taken, this problem may …

We study analytically and numerically the evolution of bound systems in universes with
accelerating expansion where the acceleration either increases with time towards a Big Rip …