Astrophysical constraints on primordial black holes in Brans-Dicke theory

TL;DR

This paper investigates how primordial black holes in Brans-Dicke theory influence cosmological evolution and astrophysical constraints, emphasizing the role of radiation accretion in extending black hole lifetimes and tightening initial mass fraction limits.

Contribution

It provides a detailed analysis of astrophysical constraints on primordial black holes within Brans-Dicke theory, highlighting the impact of radiation accretion on these constraints.

Findings

Accretion extends black hole lifetimes during radiation era.

Constraints on initial black hole mass fractions are tighter with higher accretion efficiency.

Hawking radiation affects cosmic microwave background and element abundances.

Abstract

We consider cosmological evolution in Brans-Dicke theory with a population of primordial black holes. Hawking radiation from the primordial black holes impacts various astrophysical processes during the evolution of the Universe. The accretion of radiation by the black holes in the radiation dominated era may be effective in imparting them a longer lifetime. We present a detailed study of how this affects various standard astrophysical constraints coming from the evaporation of primordial black holes. We analyze constraints from the present density of the Universe, the present photon spectrum, the distortion of the cosmic microwave background spectrum and also from processes affecting light element abundances after nucleosynthesis. We find that the constraints on the initial primordial black hole mass fractions are tightened with increased accretion efficiency.