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Viability Constraints on Baryogenesis in f (R, Lm, T) Gravity

Kalyan Malakar, Rajdeep Mazumdar, Mrinnoy M Gohain, Kalyan Bhuyan

TL;DR

The paper investigates gravitational baryogenesis within the generalized gravity $f(R,L_m,T)$, focusing on a linear model $f(R,L_m,T)=\alpha R+\beta L_m+\gamma T$ and a power-law cosmology to generate the baryon-to-entropy ratio $\eta_B/s$. By deriving the modified field equations and employing a CP-violating coupling to curvature and matter, it computes $\eta_B/s$ for radiation-dominated epochs in two models and in a generalized coupling framework, showing results compatible with the observed $9.42\times 10^{-11}$. The study identifies viable parameter regions: Model I prefers strong curvature coupling with negative $\beta$, whereas Model II requires extremely small $\beta$, with the generalized case broadening the viable space. Overall, $f(R,L_m,T)$ gravity can provide a consistent, early-universe mechanism for the matter–antimatter imbalance, aligning with current cosmological data and potentially offering a flexible platform for baryogenesis scenarios.

Abstract

Our study explores gravitational baryogenesis in the context of f(R, Lm, T) gravity, where R denotes the Ricci scalar, Lm represents the Lagrangian density of the matter field, and T stands for the metric contraction of T_{mu nu}. We focus on a linear model: f(R, Lm, T) = alpha R + beta Lm + gamma T, and examine the parameter constraints for a successful baryon asymmetry generation in four different eras of the cosmos under the assumption of a power-law cosmic expansion. The computed baryon-to-entropy ratio is found to be consistent with the observed order of asymmetry ratio, 9.42 x 10^-11. Furthermore, the study is extended to the generalized framework of gravitational baryogenesis, where the outcome shows strong agreement with the current observational data. Our findings indicate that the f(R, Lm, T) framework provides a compatible theoretical foundation for producing the observed matter imbalance of the cosmos, thereby emphasizing its potential significance in early-universe cosmology.

Viability Constraints on Baryogenesis in f (R, Lm, T) Gravity

TL;DR

The paper investigates gravitational baryogenesis within the generalized gravity , focusing on a linear model and a power-law cosmology to generate the baryon-to-entropy ratio . By deriving the modified field equations and employing a CP-violating coupling to curvature and matter, it computes for radiation-dominated epochs in two models and in a generalized coupling framework, showing results compatible with the observed . The study identifies viable parameter regions: Model I prefers strong curvature coupling with negative , whereas Model II requires extremely small , with the generalized case broadening the viable space. Overall, gravity can provide a consistent, early-universe mechanism for the matter–antimatter imbalance, aligning with current cosmological data and potentially offering a flexible platform for baryogenesis scenarios.

Abstract

Our study explores gravitational baryogenesis in the context of f(R, Lm, T) gravity, where R denotes the Ricci scalar, Lm represents the Lagrangian density of the matter field, and T stands for the metric contraction of T_{mu nu}. We focus on a linear model: f(R, Lm, T) = alpha R + beta Lm + gamma T, and examine the parameter constraints for a successful baryon asymmetry generation in four different eras of the cosmos under the assumption of a power-law cosmic expansion. The computed baryon-to-entropy ratio is found to be consistent with the observed order of asymmetry ratio, 9.42 x 10^-11. Furthermore, the study is extended to the generalized framework of gravitational baryogenesis, where the outcome shows strong agreement with the current observational data. Our findings indicate that the f(R, Lm, T) framework provides a compatible theoretical foundation for producing the observed matter imbalance of the cosmos, thereby emphasizing its potential significance in early-universe cosmology.

Paper Structure

This paper contains 18 sections, 41 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Description of $f(R, L_{m}, T)$ gravity and Field Equations
  3. Review on $f(R, L_{m}, T)$ Gravity
  4. Field equations
  5. Overview of Gravitational Baryogenesis
  6. Gravitational Baryogenesis in $f(R, L_{m}, T)$
  7. Model I
  8. Radiation-dominated era ($\omega=\frac{1}{3}$)
  9. Model II
  10. Radiation-dominated era ($\omega=\frac{1}{3}$)
  11. Generalized Gravitational Baryogenesis in $f(R, L_{m}, T)$
  12. Model I
  13. Radiation-dominated era ($\omega=\frac{1}{3}$)
  14. Model II
  15. Radiation-dominated era ($\omega=\frac{1}{3}$)
  16. ...and 3 more sections

Figures (4)

  • Figure 1: Plot of $\frac{\eta_B}{s}$ versus $\alpha$ for the $f(R,L_m,T)$ model I under consideration in radiation era $(\omega=\frac{1}{3})$ for three different $\beta$ choices.
  • Figure 2: Plot of $\frac{\eta_B}{s}$ versus $\alpha$ for the $f(R,L_m,T)$ model II under consideration in radiation era $(\omega=\frac{1}{3})$ for three different $\beta$ choices.
  • Figure 3: Plot of $\frac{\eta_B}{s}$ versus $\alpha$ (generalized case) for the $f(R,L_m,T)$ model I under consideration in radiation era $(\omega=\frac{1}{3})$ for three different $\beta$ choices.
  • Figure 4: Plot of $\frac{\eta_B}{s}$ versus $\alpha$ (generalized case) for the $f(R,L_m,T)$ model II under consideration in radiation era $(\omega=\frac{1}{3})$ for three different $\beta$ choices.