Effect of Vacuum Energy on Evolution of Primordial Black Holes in Einstein Gravity

TL;DR

This paper investigates how vacuum energy influences the evolution, mass, and lifespan of primordial black holes, revealing that vacuum energy can extend their lifetime and tighten initial mass constraints.

Contribution

It introduces a model considering vacuum energy dominance in black hole evolution, showing increased lifespans and altered accretion dynamics compared to previous analyses.

Findings

Radiation accretion efficiency must be less than 0.366

Primordial black holes live longer due to higher accretion rates

Vacuum energy accretion affects black holes only up to a critical time

Abstract

We study the evolution of primordail black holes by considering present universe is no more matter dominated rather vacuum energy dominated. We also consider the accretion of radiation, matter and vacuum energy during respective dominance period. In this scenario, we found that radiation accretion efficiency should be less than 0.366 and accretion rate is much larger than previous analysis by B. Nayak et al. \cite{ns}. Thus here primordial black holes live longer than previous works \cite{ns}. Again matter accretion slightly increases the mass and lifetime of primordial black holes. However, the vacuum energy accretion is slightly complicated one, where accretion is possible only upto a critical time. This critical time depends on the values of accretion efficiency and formation time. If a primordial black hole lives beyond critical time, then its lifespan increases due to vacuum energy accretion. But for presently evaporating primordial black holes, critical time comes much later than their evaporating time and thus vacuum energy could not affect those primordial black holes. We again found that the constraints on the initial mass fraction of PBH obtained from the $\gamma$-ray background limit becomes stronger in the presence of vacuum energy.