Baryon asymmetry from Barrow entropy: theoretical predictions and observational constraints

Abstract

We investigate the generation of baryon asymmetry from the corrections brought about in the Friedman equations due to Barrow entropy. In particular, by applying the gravity-thermodynamics conjecture one obtains extra terms in the Friedmann equations that change the Hubble function evolution during the radiation-dominated epoch. Hence, even in the case of standard coupling between the Ricci scalar and baryon current they can lead to a non-zero baryon asymmetry. In order to match observations we find that the Barrow exponent should lie in the interval $$0.005\lesssim \Delta \lesssim 0.008$$ 0.005 ≲ Δ ≲ 0.008 , which corresponds to a slight deviation from the standard Bekenstein–Hawking entropy. The upper bound is tighter than the one of other observational constraints, however the interesting feature is that in the present analysis we obtain a non-zero lower bound. Nevertheless this lower bound would disappear if the baryon asymmetry in Barrow-modified cosmology is generated by other mechanisms, not related to the Barrow modification.

Cosmic evolution and thermal stability of Barrow holographic dark energy in nonflat Friedmann-Robertson-Walker Universe

“…Minimization of deviation of R 2 from unity gives the best-fit values b = 0.12 and ∆ = 0.08 at 95% confidence level. We notice that the obtained estimation of Barrow parameter fits with the result ∆ = 0.094 +0.093 −0.101 derived in [26] and is very close to the constraint ∆ = 0.075 +0.001 −0.002 of [76], but it lies outside the intervals 0.005 ≤ ∆ ≤ 0.008 [32] and ∆ 1.4 × 10 −4 [28] found via baryogenesis and Big Bang Nucleosynthesis measurements, respectively. This discrepancy might be understood by assuming a HDE description of the Universe with a running Barrow entropy, as discussed in [77].…”

“…Corrections to the standard entropy-area law are parameterized by the exponent 0 ≤ ∆ ≤ 1, where ∆ = 0 recovers the Bekenstein-Hawking limit, while ∆ = 1 corresponds to the maximal entropy deformation. It is worth noting that upper bounds on ∆ have been derived in different contexts in [26][27][28][29][30][31][32][33].…”

“…( 1) is commonly adopted also in Cosmology [35][36][37][38][39][40] to derive modified Friedmann equations from the first law of thermodynamics on the apparent horizon of a Friedmann-Robertson-Walker (FRW) Universe. The ensuing framework is referred to as Barrow Holographic Dark Energy (BHDE) and exhibits a richer phenomenology compared to HDE, allowing us to predict effects beyond the domain of the Standard Model of Cosmology for certain values of ∆ (see, for instance, [32]).…”

Kaniadakis holographic dark energy in Brans–Dicke cosmology

“…Quantum gravity effects are parameterized by the Barrow exponent 0 ≤ ∆ ≤ 1, with ∆ = 0 giving the BH limit, while ∆ = 1 corresponding to the maximal entropy deformation. It is worth mentioning that cosmological constraints on ∆ have been inferred in [47][48][49][50][51][52][53][54].…”

An attempt to add Barrow entropy in f(R) gravity

“…In this context, some applications have been investigated. For example, Baryon asymmetry has been studied [25], inflation driven by Barrow holographic dark energy has been considered [26], early and late periods of the universe from a new generalized entropy have been analyzed [27], Barrow holographic dark energy has been formulated [28], the cosmology using Barrow entropy has been proposed [29], the generalized second law of thermodynamics with Barrow entropy has been investigated [30], among others. In this context, the main objective of this paper is to analyze the dynamic evolution of the universe considering the Barrow entropy in f (R) gravity.…”