Note on nonstationarity and accretion of Primordial Black Holes in Brans-Dicke theory

TL;DR

This paper investigates how non-stationarity and radiation accretion influence the evolution and constraints of primordial black holes within Brans-Dicke theory, highlighting the roles of formation fraction and accretion efficiency.

Contribution

It introduces a model incorporating non-stationarity and radiation accretion in primordial black hole evolution in Brans-Dicke theory, emphasizing the combined effect of formation fraction and accretion efficiency.

Findings

Primordial black hole dynamics depend on the product of accretion efficiency and formation fraction.

The initial mass fraction constraints are affected by non-stationarity and accretion effects.

The model provides a refined understanding of primordial black hole evolution in alternative gravity theories.

Abstract

We consider the evolution of primordial black holes by including non-stationarity in their formation process and accretion of radiation in Brans-Dicke theory. Specifically, we focus on how $\eta$, the fraction of the horizon mass the black hole comprises capturing nonstationarity, affects the lifetimes of these primordial black holes. Our calculation reveals that the primordial black hole dynamics is controlled by the product $f\eta$ where $f$ is the accretion efficiency. We also estimate the impact of $\eta$ through $f\eta$ on the primordial black holes' initial mass fraction constraint obtained from the $\gamma$-ray background limit.