Dark energy: Vacuum fluctuations, the effective phantom phase, and holography

Abstract

We aim at the construction of dark energy models without exotic matter but with a phantom-like equation of state (an effective phantom phase). The first model we consider is decaying vacuum cosmology where the fluctuations of the vacuum are taken into account. In this case, the phantom cosmology (with an effective, observational ω being less than −1 ) emerges even for the case of a real dark energy with a physical equation of state parameter ω larger than −1. The second proposal is a generalized holographic model, which is produced by the presence of an infrared cutoff. It also leads to an effective phantom phase, which is not a transient one as in the first model. However, we show that quantum effects are able to prevent its evolution towards a Big Rip singularity.

Phenomenological Fluids from Interacting Tachyonic Scalar Fields

“…Alternative models of dark energy suggest a dynamical form of dark energy, which at least in an effective level, can originate from a variable cosmological constant [24,25], or from various fields, such as a canonical scalar field [26][27][28][29][30] (quintessence), a phantom field [31][32][33][34][35][36][37][38] or the quintom [39][40][41][42][43][44][45][46][47][48][49][50][51]. By using some basic of quantum gravitational principles, we can formulate several other models for dark energy and in literature they are known as holographic dark energy paradigm [52][53][54][55][56][57][58][59][60][61][62][63] and agegraphic dark energy models [64][65][66].…”

The phantom divide in string gas cosmology

“…We do not necessarily regard this field as "matter" in the ordinary sense -it may simply parametrize the effects of higherorder curvature terms, of quantum effects [31][32], of brane-world physics, or other such contributions arising from the embedding of the system in higher-dimensional physics [29][30] [28][33] [34]. We are interested in determining whether an NEC-violating cosmology can be stable against brane pair-production.…”

Can holographic dark energy increase the mass of the wormhole?

“…Using the above expansion (26) we have at very late stage i.e. z → − 1 the mass of wormhole as HDE, HRDE and MHRDE accretion occurs as follows:…”

“…Wormholes are expected usually due to quantum effects [24,25]. They inspired from the quantum effects [26,27]. Different aspects of wormholes are widely studied in literature from general relativity to modified gravities [18]- [21].…”