Corrected Entropy-area Relation Research Articles

A NON-SINGULAR CLOSED BOUNCING UNIVERSE WITHOUT VIOLATION OF NULL ENERGY CONDITION

A matter bouncing entropy-corrected cosmological model has been suggested. The model allows only positive curvature with negative pressure and no violation of the null energy condition. The result obtained in this paper is supported by some recent theoretical works where the combination of positive spatial curvature and vacuum energy leads to non-singular bounces with no violation of the null energy condition. An important feature of the current model is that evolutions of the cosmic pressure, energy density and equation of state parameter are independent of the values of the prefactors α and β in the corrected entropy-area relation. The validity of the classical and the new nonlinear energy conditions has been discussed. The cosmographic parameters have been analyzed.

A stable flat entropy-corrected FRW universe

In this paper, a general entropy-corrected FRW cosmological model has been presented in which a deceleration-to-acceleration transition occurs according to recent observations. We found that the case for the flat universe ([Formula: see text]), supported by observations, is the most stable one where it successfully passes all stability tests. The stability of the model has been studied through testing the sound speed, the classical and the new nonlinear energy conditions. The model predicts a positive pressure during the early-time decelerating epoch, and a negative pressure during the late-time accelerating epoch in a good agreement with cosmic history and dark energy assumption. We have investigated all possible values of the prefactors [Formula: see text] and [Formula: see text] in the corrected entropy-area relation to find the best values required for a stable flat universe. We have also made use of the evolution of the equation of state parameters [Formula: see text] in predicting the correct values of [Formula: see text] and [Formula: see text]. The jerk and density parameters have been calculated where a good agreement with observations and [Formula: see text]CDM model has been obtained. Two dark energy proposals have been investigated in this model, the entropy-corrected holographic dark energy and the modified holographic Ricci dark energy.

Cosmological determination to the values of the pre-factors in the logarithmic corrected entropy-area relation

In this paper, we continue investigating the possible values of the pre-factors $\alpha$ and $\beta$ in the logarithmic corrected entropy-area relation based on cosmological stability arguments. In a previous study, we have investigated the stability of the entropy-corrected cosmology using an empirical hyperbolic form of the scale factor. We found that the zero values of the two pre-factors are necessary to obtain a stable flat universe with a deceleration-acceleration transition and no causality violation. The necessity of the zero values of the two pre-factors has also been reached in the current work using a hybrid scale factor Ansatz in the entropy-corrected cosmological equations. Investigating the corrected entropy-area relation in different gravitational and cosmological contexts can provide an accurate estimation to the correct values of the pre-factors. The current work opens a discussion on the validity of the correction terms in the logarithmic corrected entropy-area relation on the cosmological scale. The evolution of the cosmic pressure, energy density, equation of state parameter, jerk parameter and the nonlinear energy conditions has been analyzed.

How Can the Modified Dispersion Relation Affect Friedmann Equations?

The appearance of the quantum gravitational effects in a very high energy regime necessitates some corrections to the thermodynamics of Friedmann-Robertson-Walker (FRW) universe. The modified dispersion relation (MDR) as a phenomenological approach to investigate the high energy physics provides a perturbation framework upon which the FRW universe thermodynamics can be corrected. In this letter, we obtain the corrected entropy-area relation of the apparent horizon of FRW universe by utilizing the extra dimensional form of MDR, leading to the modification of Friedmann equations. The influence of MDR on the Friedmann equations provides a good insight into the understanding of the FRW universe dynamics in the final quantum gravity theory.

Thermodynamics of apparent horizon in modified FRW universe with power-law corrected entropy

We derive the modified Friedmann equation corresponding to the power-law corrected entropy-area relation $S_{\rm A}=\frac{A}{4}[1-K_{\alpha} A^{1-\frac{\alpha}{2}}]$ which is motivated by the entanglement of quantum fields in and out of the apparent horizon. We consider a non-flat modified FRW universe containing an interacting viscous dark energy with dark matter and radiation. For the selected model, we study the effect of the power-law correction term to the entropy on the dynamics of dark energy. Furthermore, we investigate the validity of the generalized second law (GSL) of gravitational thermodynamics on the apparent horizon and conclude that the GSL is satisfied for $\alpha<2$.

Corrected entropy-area relation and modified Friedmann equations

Applying Clausius relation, δQ = TdS, to apparent horizon of a FRW universe with any spatial curvature, and assuming that the apparent horizon has temperature T = 1/(2πA), and a quantum corrected entropy-area relation, S = A/4G+αln A/4G, where A and A are the apparent horizon radius and area, respectively, and α is a dimensionless constant, we derive modified Friedmann equations, which does not contain a bounce solution. On the other hand, loop quantum cosmology leads to a modified Friedmann equation H2 = (8πG/3)ρ(1−ρ/ρcrit). We obtain an entropy expression of apparent horizon of FRW universe described by the modified Friedmann equation. In the limit of large horizon area, resulting entropy expression gives the above corrected entropy-area relation, however, the prefactor α in the logarithmic term is positive, which seems not consistent with most of results in the literature that quantum geometry leads to a negative contribution to the area formula of black hole entropy.