SU(2)$_R$ and its Axion in Cosmology: A common Origin for Inflation, Cold Sterile Neutrinos, and Baryogenesis

TL;DR

This paper proposes a Left-Right symmetric axion-inflation model that unifies inflation, dark matter, and baryogenesis, explaining observed cosmological coincidences through spontaneous CP violation and quantum effects during inflation.

Contribution

It introduces a novel cosmological model embedding axion-inflation in Left-Right symmetry, linking three major cosmological phenomena with minimal fine-tuning and new fundamental scales.

Findings

The model naturally explains the coincidence of cosmological parameters.

The lightest right-handed neutrino is a viable 1 GeV dark matter candidate.

Baryon asymmetry and dark matter originate from quantum effects during inflation.

Abstract

We introduce an axion-inflation model embedded in the Left-Right symmetric extension of the SM in which $W_R$ is coupled to the axion. This model merges three milestones of modern cosmology, i.e., inflation, cold dark matter, and baryon asymmetry. Thus, it can naturally explain the observed coincidences among cosmological parameters, i.e., $\eta_{B}\approx P_{\zeta}$ and $\Omega_{DM} \simeq 5~\Omega_{B}$. The source of asymmetry is spontaneous CP violation in the physics of inflation, and the lightest right-handed neutrino is the cold dark matter candidate with mass $m_{N_1}\sim 1~GeV$. The introduced mechanism does not rely on the largeness of the unconstrained CP-violating phases in the neutrino sector nor fine-tuned masses for the heaviest right-handed neutrinos. It has two unknown fundamental scales, i.e. scale of inflation $\Lambda_{\rm inf}=\sqrt{HM_{Pl}}$ and left-right symmetry breaking $\Lambda_{F}$. Sufficient matter asymmetry demands $\Lambda_{\rm inf}\approx\Lambda_{F}$. The baryon asymmetry and dark matter today are remnants of a pure quantum effect (chiral anomaly) in inflation, which, thanks to flavor effects, are memorized by cosmic evolution.