Non-Gaussian bubbles in the sky

TL;DR

This paper proposes a mechanism for generating non-Gaussian bubble-like features in the CMB due to bubble nucleation during early universe inflation, with potential for future observational detection.

Contribution

It introduces a model linking bubble nucleation to observable non-Gaussian features in the CMB, providing a novel way to probe early universe physics.

Findings

Large skewness inside bubble regions in the sky.

Potential detectability of bubble-shaped non-Gaussian features.

Insights into early universe phase transitions.

Abstract

We point out a possible generation mechanism of non-Gaussian bubbles in the sky due to bubble nucleation in the early universe. We consider a curvaton scenario for inflation and assume that the curvaton field phi, whose energy density is subdominant during inflation but which is responsible for the curvature perturbation of the universe, is coupled to another field sigma which undergoes false vacuum decay through quantum tunneling. For this model, we compute the skewness of the curvaton fluctuations due to its interaction with sigma during tunneling, that is, on the background of an instanton solution that describes false vacuum decay. We find that the resulting skewness of the curvaton can become large in the spacetime region inside the bubble. We then compute the corresponding skewness in the statistical distribution of the cosmic microwave background (CMB) temperature fluctuations. We find a non-vanishing skewness in a bubble-shaped region in the sky. It can be large enough to be detected in the near future, and if detected it will bring us invaluable information about the physics in the early universe.