ﻻ يوجد ملخص باللغة العربية
In this paper we analyse the possibility of having homogeneous isotropic cosmological models with observers reaching $t=infty$ in finite proper time. It is shown that just observationally-suggested dark energy models with $win(-5/3,-1)$ show this feature and that they are endowed with an exotic curvature singularity. Furthermore, it is shown that non-accelerated observers in these models may experience a duration of the universe as short as desired by increasing their linear momentum. A subdivision of phantom models in two families according to this behavior is suggested.
We consider cosmological models with a dynamical dark energy field, and study the presence of three types of commonly found instabilities, namely ghost (when fields have negative kinetic energy), gradient (negative momentum squared) and tachyon (nega
We study the phase space of the quintom cosmologies for a class of exponential potentials. We combine normal forms expansions and the center manifold theory in order to describe the dynamics near equilibrium sets. Furthermore, we construct the unstab
We propose a dark energy model with a logarithmic cosmological fluid which can result in a very small current value of the dark energy density and avoid the coincidence problem without much fine-tuning. We construct a couple of dynamical models that
I discuss the dark energy characterized by the violation of the null energy condition ($varrho + p geq 0$), dubbed phantom. Amazingly, it is admitted by the current astronomical data from supernovae. We discuss both classical and quantum cosmological
We consider a cosmology with decaying metastable dark energy and assume that a decay process of this metastable dark energy is a quantum decay process. Such an assumption implies among others that the evolution of the Universe is irreversible and vio