Unified Origin of Curvature Perturbation and Baryon Asymmetry of the Universe

TL;DR

This paper presents a unified model combining the curvaton and Affleck-Dine mechanisms to explain both primordial density fluctuations and baryon asymmetry, predicting observable non-Gaussianity consistent with current data.

Contribution

It introduces a novel analytical approach using the $ abla$ formalism to accurately compute scalar fluctuations in a unified curvaton-AD framework.

Findings

The model produces the correct scalar power spectrum with a negative $f_{NL}$.

The scenario is consistent with Planck data and testable by future experiments.

The radial component acts as a curvaton, generating density fluctuations, while the angular component explains baryon asymmetry.

Abstract

We propose a unified framework that describes both the curvaton mechanism for generating primordial density fluctuations and the Affleck-Dine (AD) mechanism for baryogenesis. By introducing a complex scalar field (AD field) carrying a baryon/lepton number and its potential consisting of quadratic and quartic terms with a small baryon/lepton-number-violating mass term, we investigate the evolution of the scalar field during the radiation-dominated era following inflation. We set the initial conditions such that the quartic term dominates the scalar potential, and the angular component of the AD field is non-zero. We focus on a scenario where the AD field sufficiently dominates the energy density of the universe before its decay. We show that the radial component of the AD field can be identified with the curvaton to solely produce the Planck normalized scalar power spectrum while the evolution of the angular component is crucial for generating the observed baryon asymmetry of the universe. Additionally, we find that the amplitude of scalar bispectrum $f_{NL}$ is negative, which is consistent with the current Planck data and testable in future observations such as CMB-S4, LiteBIRD, LSS, and 21-cm experiments. In our estimation of the scalar power spectrum and bispectrum, we develop a novel analytical scheme for computing scalar fluctuations based on the $\delta N$ formalism, which allows us to deal with the evolution of curvaton with polynomial potential more accurately in comparison to the existing analytical methods.