Cosmological and thermodynamics analysis in Weyl gravity

Abstract

In the framework of modified Weyl gravity, we observe the equilibrium picture of the thermodynamical laws for flat Friedmann-Robertson-Walker metric with chameleon scalar field and analyze the validity of the generalized second law of thermodynamics and thermal equilibrium condition for Hubble horizon along with Bekenstien-Hawking entropy. Also, we examine the effective equation of state parameter as well as the square speed of sound. By assuming four different choices of deceleration parameter, we investigate the behavior of equation of state parameter as well as the square speed of sound. The validity of generalized second law of thermodynamics and thermal equilibrium condition is also checked by taking the observational values of the model parameters from CC+H o dataset.

Cosmological solutions of modified F (T ) gravity with Dirac field

“…Moreover, for our cosmological model with H(z) quadratic expansion, the constrained value of the deceleration parameter using the combined Hubble+Pantheon+BAO dataset is q 0 = −0.285 ± 0.021. This value is in agreement with previous studies that employed similar techniques to estimate q 0 [46,[60][61][62]. The transition from deceleration to the acceleration phase in f (Q) gravity under various assumptions is discussed by [7][8][9][10].…”

“…Now, we require one further ansatz to examine the evolution of the cosmological parameters. In the literature, there are various justifications for using these equations [44][45][46][47][48][49][60][61][62]. The technique is well famous as the model-independent way to study cosmological models because it generally considers parametrizations of any kinematic parameters such as the Hubble parameter, deceleration parameter, and jerk parameter and gives the necessary extra equation.…”

Compatibility of big bang nucleosynthesis in some modified gravities

“…We have chosen the fixed constants as H 0 = 0.69, β = 0.6 and M = 5. It can be observed from the figure that the mathematical relation (51) satisfies the bound (40) for n ≤ 0.7498. Moreover, if we restrict the free parameter n near zero, then the bound coming in (39) becomes constant which justify the CDM regime.…”

A model-independent method with phantom divide line crossing in Weyl-type f(Q,T) gravity

“…As SNe Ia measurements and other astronomical observations suggest that the cosmos is accelerating, a timedependent deceleration parameter is necessary to explain the transition from deceleration expansion in the past to accelerating expansion in the present. In line with this idea, different parametrizations have argued that deceleration parameter is time-dependent in order to examine various cosmological difficulties [42][43][44][45][46][47][48][49][50][51][52][53]. Motivated by the preceding debate, we use a generalization form of the deceleration parameter proposed in Eq.…”