Abstract The Nobel Prize winning confirmation in 1998 of the accelerated expansion of our
Universe put into sharp focus the need of a consistent theoretical model to explain the origin …

We review in detail a number of approaches that have been adopted to try and explain the
remarkable observation of our accelerating universe. In particular we discuss the arguments …

Recent cosmological observations suggest the existence of a positive cosmological constant
Λ with the magnitude Λ (Gℏ/c3)≈ 10− 123. This review discusses several aspects of the …

It is an accepted practice in cosmology to invoke a scalar field with a potential V (φ) when
the observed evolution of the universe cannot be reconciled with theoretical prejudices …

Traversable wormholes necessarily require violations of the averaged null energy condition,
this being the definition of “exotic matter.” However, the theorems which guarantee the …

We examine k-essence models in which the Lagrangian p is a function only of the
derivatives of a scalar field φ and does not depend explicitly on φ. The evolution of φ for an …

Spacetimes with horizons show a resemblance to thermodynamic systems and it is possible
to associate the notions of temperature and entropy with them. Several aspects of this …

We present a detailed study of cosmological effects of homogeneous tachyon matter
coexisting with nonrelativistic matter and radiation, concentrating on the inverse square …

We propose an infrared cut-off for the holographic the dark energy, which besides the
square of the Hubble scale also contains the time derivative of the Hubble scale. This avoids …

The present paper is devoted to investigating the possibility of getting stellar interiors for
ultra-dense compact spherical systems portraying an anisotropic matter distribution …