CMB spectral distortions from black holes formed by vacuum bubbles

TL;DR

This paper investigates how black holes formed from vacuum bubbles during inflation could cause specific spectral distortions in the CMB, providing potential observational constraints on such models.

Contribution

It estimates the CMB spectral μ-distortions caused by shocks from vacuum bubble-formed black holes, linking early universe phenomena to observable signatures.

Findings

Predicted distortions are below current observational bounds.

Localized peaks in distortions can constrain model parameters.

Black holes from vacuum bubbles could explain dark matter and seed supermassive black holes.

Abstract

Vacuum bubbles may nucleate and expand during the cosmic inflation. When inflation ends, the bubbles run into the ambient plasma, producing strong shocks followed by underdensity waves, which propagate outwards. The bubbles themselves eventually form black holes with a wide distribution of masses. It has been recently suggested that such black holes may account for LIGO observations and may provide seeds for supermassive black holes observed at galactic centers. They may also provide a significant part or even the whole of the dark matter. We estimate the spectral $\mu$-distortion of the CMB induced by expanding shocks and underdensities. The predicted distortions averaged over the sky are well below the current bounds, but localized peaks due to the largest black holes impose constraints on the model parameters.