The possibility of a stable flat dark energy-dominated Swiss-cheese brane-world universe

Abstract

In this paper, we study the possibility of obtaining a stable flat dark energy-dominated universe in a good agreement with observations in the framework of Swiss-cheese Braneworld cosmology. Two different Brane-world cosmologies with black strings have been introduced for any cosmological constant Λ using two empirical forms of the scale factor. In both models, we have performed a fine-tuning between the brane tension and the cosmological constant so that the EoS parameter ω(t) → −1 for the current epoch where the redshift z 0. We then used these fine-tuned values to calculate and plot all parameters and energy conditions. The deceleration-acceleration cosmic transition is allowed in both models, and the jerk parameter j → 1 at late-times. Both solutions predict a future dark energy-dominated universe in which ω = −1 with no crossing to the phantom divide line. While the pressure in the first solution is always negative, the second solution predicts a better behavior of cosmic pressure where the pressure is negative only in the late-time accelerating era but positive in the early-time decelerating era. Since black strings have been proved to be unstable by some authors, this instability can actually reflect doubts on the stability of cosmological models with black strings (Swiss-cheese type brane-worlds cosmological models). For this reason, we have carefully investigated the stability through energy conditions and sound speed. Because of the presence of quadratic energy terms in Swiss-cheese type brane-world cosmology, we have tested the new nonlinear energy conditions in addition to the classical energy conditions. We have also found that constructing non-singular and cyclic solutions through certain ansatze in Swiss-cheese Brane-worlds are not possible.

Ricci–Gauss–Bonnet holographic dark energy in Chern–Simons modified gravity: A flat FLRW quintessence-dominated universe

“…• Both solutions predicting a sign-flipping from negative to positive in the evolution of p(t), the behavior which helps in explaining the observationally suggested cosmic transit from deceleration to acceleration. Such negative-to-positive transition in the evolution of cosmic pressure appears in different cosmological contexts such as cyclic universes [57], entropy-corrected cosmology [58,59], and Swiss-cheese brane-world cosmology [60]. The second solution gives a more general description to the evolution of cosmic pressure than the first one.…”

Some cosmological features of 4D Gauss-Bonnet gravity with varying cosmological constant

“…The evolution of these two parameters should lead to a cosmic deceleration-acceleration transit along with a flat ΛCDM model at late-time. This ad hoc approach for the scale factor and scalar fields has been used extensively in the literature to probe the cosmology of several gravity theories [24,25,26,27,28,29,30,31,32].…”

The symmetries of quantum and classical information

“…The global curvature of the universe can be granted to be really zero (Ries 1984;Pierpaoli 2000;Masi et al 2002;Vardanuan, Trotta, Silk 2009;Ahmed, Bamba, Salama 2020;Efstathiou, Gratton 2020). However, the reason for that is not that suggested by the "physical common sense", namely that matter and energy (including dark ones) are "infinitely sparse", so the curvature caused by them is infinitesimally small.…”