arXiv subjects

Ava Shahbazi Sooraki

Publications and source records attributed to Ava Shahbazi Sooraki.

5 recordsLinked to original sources

arXiv2026

Big-Bang Nucleosynthesis and WIMP Dark Matter Freeze-Out as Probes of Yukawa Cosmology

We investigate Big-Bang Nucleosynthesis (BBN) in the context of Yukawa cosmology. We first derive the modified Friedmann equations by starting from the first law of thermodynamics on the apparent horizon. Using observational data on $^4\mathrm{He}$, deuterium, and $^7\mathrm{Li}$ abundances, we place stringent bounds on the Yukawa coupling $α$. The $^4\mathrm{He}$ and deuterium constraints are mutually consistent ($-0.24 \lesssim α\lesssim 0.12$), while $^7\mathrm{Li}$ requires $α\in [-0.76,\,-0.72]$. This indicate that Yukawa cosmology cannot resolve the Lithium Problem. We then extend our analysis to WIMP freeze-out, and show that the modified Hubble parameter alters the relic abundance, yielding an independent constraint $-0.017 \lesssim α\lesssim 0.018$ from $Ω_{\mathrm{CDM}}h^2 = 0.120 \pm 0.001$. We also derive the modified time-temperature relation, and show that the positive $α$ raises the early Universe temperature. Our analysis demonstrates that BBN and dark matter relic abundance serve as complementary probes of modified gravity. Our studies confirm that Yukawa cosmology is a testable framework for early-Universe physics.

astro-ph.CO↗

arXiv2026

Constraints on Rényi Entropy through Primordial Big-Bang Nucleosynthesis and Baryogenesis

The Rényi entropy, a one-parameter generalization of Boltzmann-Gibbs entropy, offers a promising framework for probing quantum gravitational effects in cosmology. By modifying the entropy-area relation of the apparent horizon, Rényi entropy can alter the expansion dynamics of the early universe, with potential implications for Big-Bang Nucleosynthesis. In this work, we derive the modified Friedmann equations within the Rényi entropy paradigm and investigate their impact on the primordial abundances of light elements Deuterium ($D$), Helium-4 ($_{}^{4}\textit{He}$), Lithium-7 ($_{}^{7}\textit{Li}$) and baryogenesis. Using observational constraints from Planck, primordial abundance data and observational data on baryogenesis, we put stringent bounds on the Rényi parameter. Furthermore, we explore whether Rényi entropy corrections could mitigate the long-standing Lithium discrepancy. This study provides the first systematic constraints on Rényi cosmology from BBN and highlights the role of nonextensive thermodynamics in early-universe physics. Our analysis shows that the obtained ranges for the Rényi parameter $λ$ exhibit a overlap for the Helium-4 and Deuterium, but this overlapping region-despite a small discrepancy-is inconsistent with the range obtained from Lithium-7. This small mismatch between the ranges raises the possibility of alleviating the \textit{Lithium Problem} in the modified cosmology scenarios. Furthermore, we present the relationship between the cosmic time and temperature within the framework of Rényi cosmology. We observe that an increase in the Rényi parameter increase the temperature of the early universe.

physics.gen-ph↗

arXiv2026

Constraining Zero-Point Length from Gravitational Baryogenesis

The existence of a fundamental zero-point length, $l_0$, a minimal spacetime scale predicted by T-duality in string theory or quantum gravity theories, modifies the entropy associated with the horizon of spacetime. In the cosmological setup, this leads to correction to the Friedmann equations governing the evolution of the Universe. In this paper, we investigate the implications of zero-point length $l_0$-corrected gravity for gravitational baryogenesis and early universe thermodynamics, deriving constraints on $l_0$ from observational baryon asymmetry data. We observe that under the condition of non-equilibrium thermodynamics, $l_0$ generates $\dot{\mathcal{R}}\neq 0$ during radiation epoch, where $\mathcal{R}$ is the Ricci scalar. This yields a baryon asymmetry parameter $η\propto l_0^2 T_D^9/M_{\rm Pl}^7$. The observed baryon asymmetry $η\sim 9.9 \times 10^{-11}$ constrains $l_0 \lesssim 7.1 \times 10^{-33} m$, approximately $440$ times the Planck length. Furthermore, our analysis reveals that the zero-point length correction in the Friedmann equation, effectively slows the expansion rate at high energies, resulting in a modified time-temperature relationship where the Universe maintains higher temperatures for longer time during early epochs compared to standard cosmology. Our results establish zero-point length cosmology as a testable framework connecting quantum gravity to cosmological observables, with implications for early universe thermal history and fundamental length scales.

gr-qc↗

arXiv2025

Barrow Cosmology and Big-Bang Nucleosynthesis

Using thermodynamics-gravity conjecture, we present the formal derivation of the modified Friedmann equations inspired by the Barrow entropy, $S\sim A ^{1+δ/2}$, where $0\leqδ\leq 1$ is the Barrow exponent and $A$ is the horizon area. We then constrain the exponent $δ$ by using Big-Bang Nucleosynthesis (BBN) observational data. In order to impose the upper bound on the Barrow exponent $δ$, we set the observational bound on $\left| \frac{δT_f} {T_f }\right|$. We find out that the Barrow parameter $δ$ should be around $ δ\simeq 0.01$ in order not to spoil the BBN era. Next we derive the bound on the Barrow exponent $δ$ in a different approach in which we analyze the effects of Barrow cosmology on the primordial abundances of light elements i.e. Helium $_{}^{4}\textit{He}$, Deuterium $D$ and Lithium $_{}^{7}\textit{Li}$. We observe that the deviation from standard Bekenstein-Hawking expression is small as expected. Additionally we present the relation between cosmic time $t$ and temperature $T$ in the context of modified Barrow cosmology. We confirm that the temperature of the early universe increases as the Barrow exponent $δ$ (fractal structure of the horizon) increases, too.

gr-qc↗

arXiv2025

Big-Bang nucleosynthesis constraints on (dual) Kaniadakis cosmology

We investigate the concept of Kaniadakis entropy and its dual formulation, examining their implications for gravitational dynamics within the framework where gravity emerges as an entropic force resulting from changes in the informational content of a physical system. In this context, we derive a modified form of Newton's law of gravitation that reflects the corrections introduced by both Kaniadakis entropy and its dual state. Furthermore, we apply the emergent gravity scenario at large scales and derive the modified Friedmann equations incorporating corrections from (dual) Kaniadakis entropy. Our results provide deeper insights into the interplay between thermodynamics and gravitational dynamics. In order to constrain the model parameter, we study the Big-Bang Nucleosynthesis in the context of (dual) Kaniadakis cosmology. We explore an alternative method to establish limits on the Kaniadakis parameter, denoted as $K$, by examining how (dual) Kaniadakis cosmology influences the primordial abundances of light elements i.e. Helium $_{}^{4}\textit{He}$, Deuterium $D$ and Lithium $_{}^{7}\textit{Li}$. Our analysis indicates that the obtained ranges for the dual Kaniadakis parameter (unlike the Kaniadakis parameter) exhibit overlap for the aforementioned light elements, and the allowed values fall within the range $ -0.8\times 10^{-78}\lesssim \tilde {K^*}\lesssim 0.8\times 10^{-78}$, which shows that the deviations from the conventional Bekenstein-Hawking formula are minimal, as expected. This consistency between the ranges suggests a potential solution to the well-known \textit{Lithium problem}. Furthermore, we discuss the relationship between cosmic time $t$ and temperature $T$ within the framework of (dual) Kaniadakis cosmology.

gr-qc↗