Quantum Hubble horizon

Abstract

The article addresses the possibility of obtaining cosmologically relevant effects from the quantum nature of the Hubble horizon. Following the observation made by Bianchi and Rovelli (Phys Rev D 84:027502, 2011) we explore the relationship between the Planck scale discreteness of the Hubble horizon and deformations of the symmetry of rotations. We show that the so-called q-deformations in a natural way lead to a mechanism of condensation in the very early Universe. We argue that this provides a possible resolution of the problem of the initial homogeneity at the onset of inflation. Furthermore, we perform an analysis in terms of entropy of the quantum Hubble horizon and show that the CDM model may arise from a linearly corrected Bekenstein-Hawking entropy (that is, linearly in area of the horizon). Based on this, we show that the current accelerating expansion can be associated with the entropy decrease in the Hubble volume. The results presented open new ways to explore the relation between the Planck scale effects and observationally relevant features of our Universe.

Different Faces of Generalized Holographic Dark Energy

“…where in the second line, we useḢ = −4πGφ 2 . Equation (58) shows that the quintessence energy density is not symmetric with respect to the Hubble parameter, unlike the case of entropic dark energy models (that we considered earlier) where the entropic energy density proves to be symmetric with respect to the Hubble parameter. The exponential form of the quintessence potential (see Equation ( 56)) allows the following solutions of the Hubble parameter and the scalar field:…”

“…In the studies, we found that the FRW equations can be also regarded as the first law of thermodynamics when we consider the Bekenstein-Hawking entropy by using the cosmological apparent horizon [83][84][85] as a realization of the thermodynamics of space-time [80]. If, however, there are long range forces, such as the electromagnetic force and the gravitational force, we know that the systems are non-additive systems and the standard Boltzmann-Gibbs additive entropy should not be applied and we should generalize the entropy to the non-extensive Tsallis entropy [49][50][51], and recently there were several attempts in this regard (see [52][53][54][55][56][57][58][59][60][61][62]). If we apply Tsallis entropy to the black hole, instead of Bekenstein-Hawking entropy, one finds [52],…”

“…In the present paper, we intend to address the above questions. For this purpose, we consider several entropic DE models, such as the Tsallis entropic DE [49][50][51][52][53][54][55][56][57][58][59][60][61][62], the Rényi entropic DE [63][64][65][66][67][68], and the Sharma-Mittal entropic DE [67,69,70]. Here it may be mentioned that unlike the Tsallis and Rényi entropy functions, Sharma-Mittal entropy represents a more general two-parameter function.…”

Modified cosmology from extended entropy with varying exponent

“…Hence, neglecting the matter sector, Eqs. 41, (42) give rise to inflationary de Sitter solutions. In particular, for b 1 = 0 we obtain…”

“…Recently, there have appeared some works in the literature in which the above thermodynamical consideration is applied using extended entropy relations instead of the usual one [36][37][38][39][40][41][42][43][44][45][46]. In particular, it is known that in the case of non-additive systems, such as gravitational ones, the standard Boltzmann-Gibbs additive entropy should be generalized to the non-extensive Tsallis entropy [47][48][49], which can be applied in all cases, possessing the former as a limit.…”