Generic scenarios of the accelerating Universe

Abstract

Recent astronomical observations strongly indicate that the current Universe is undergoing an accelerated phase of its expansion. If the Universe evolution is described by the FRW model then the acceleration should be driven by some perfect substance violating the strong energy condition. Hence the negative pressure is required for the explanation of acceleration. While different candidates for the fluid termed dark energy have been suggested, the positive cosmological constant seems to be the simplest candidate for dark energy description. However the Lambda term treated as a quantum vacuum energy has no simple physical interpretation because of the fine tuning problem. In this paper we characterize a certain class of evolutional scenario of the accelerating universe from the point of view genericity expressed in notion of structural stability. It is shown that in this class all evolutional scenarios with transient acceleration effect are not generic. Only the LCDM model with the acceleration phase following the deceleration phase is structurally stable. Because the cosmological models with transient acceleration appear in string theory we conclude that they are not generic.

Falsifying cosmological models based on a non-linear electrodynamics

“…We perform a phase-space analysis of Einstein-NED cosmology without a matter source and including it. The advantage of the using phase-space analysis [41][42][43][44][45][46][47][48][49][81][82][83][84][85][86][87][88][89][90][91] is that one can do more stability analysis with using visual plots using the trajectories in geometrical way so that it becomes easy to observe the property with the help of the attractors which are the most easily seen experimentally [92]. On the other hand, conceptually using NED has the advantage that no need to use some exotic fields such as scalar fields, branes or extra dimensions, it is just photon fields, and it is well known also in nonlinear optics which studying behavior of light in nonlinear media and also nonlinear collision of particles in quantum electrodynamics [93][94][95][96][97][98][99].…”