We revisit the conjecture of a generalized second law of thermodynamics which states that the combined entropy of matter and horizons must grow. In an expanding universe a generalized second law restricts the equation of state. In particular, it conflicts with long phases of a phantom, w < −1, equation of state.

We review recent work and present new examples about the character of singularities in globally and regularly hyperbolic, isotropic universes. These include recent singular relativistic models, tachyonic and phantom universes as well as inflationary cosmologies.

In this paper we will investigate the validity of the Generalized Second Law of thermodynamics for the Quintom model of dark energy. Reviewing briefly the quintom scenario of dark energy, we will study the conditions of validity of the generalized second law of thermodynamics in three cases: quintessence dominated, phantom dominated and transition from quintessence to phantom will be discussed.

We have found an exact solution of spherically symmetrical Einstein equations describing a black hole with a special type phantom energy source. It is surprising to note that our solution is analogous to Reissner-Nordström black hole. Recent astrophysical observations have confirmed that the Universe at present is expanding with an acceleration. It is proposed that this unexpected cosmological ...

We introduce a fast and well-structured package for constructing voxel-based computational phantoms as MCNP(X) input file based on CT DICOM images. Our program which has been implemented under a graphic user inter-face provides several basic image processing tools for manipulating images. The MCNP materials are interpreted from the CT numbers of DICOM images. Two modes of phantom creation have ...

We discuss the model consisting of tachyon which may have the negative kinetic energy plus scalar phantom and plus conformal quantum matter. It is demonstrated that such a model naturally admits two deSitter phases where the early universe inflation is produced by quantum effects and the late time accelerating universe is caused by phantom/tachyon. The energy conditions bounds for such cosmolog...

Introduction. The recently discovered acceleration of the universe [1, 2] indicates that its large-scale evolution is dominated by unknown dark energy which violates at least the strong energy condition, and perhaps also the weak energy condition, where it is known as phantom energy [3]. Such phantom energy is precisely what is needed to support traversable wormholes [4, 5, 6, 7, 8, 9]. This Le...