Gravitational Baryogenesis: Problems and Possible Resolution

TL;DR

This paper addresses the instability issues in gravitational baryogenesis caused by higher-order equations of motion and proposes a stabilization mechanism through an $R^2$ modification of gravity, impacting standard cosmology.

Contribution

It introduces an $R^2$ term to stabilize gravitational baryogenesis, resolving instability problems and analyzing the resulting parameter space.

Findings

Stabilization of $R$ achieved with $R^2$ modification.

Parameter regions for stable $R$ identified.

Standard cosmology is significantly affected.

Abstract

The coupling of baryonic current to the derivative of the curvature scalar, $R$, inherent to gravitational baryogenesis (GBG), leads to a fourth order differential equation of motion for $R$ instead of the algebraic one of General Relativity (GR). The fourth-order differential equation is generically unstable. We consider a possible mechanism of stabilization of GBG by modification of gravity, introducing an $R^2$-term into the canonical action of GR. It is shown that this mechanism allows for stabilization of GBG with bosonic and fermionic baryon currents. We have established the region of the model parameters leading to stabilization of $R$. Still, the standard cosmology would be noticeably modified.