Neutrino cooling effect of primordial hot areas in dependence on its size

TL;DR

This paper investigates how primordial hot areas in the universe, potentially formed by density fluctuations and surviving as black hole clusters, cool via neutrino emissions, especially at temperatures above 3 MeV.

Contribution

It introduces a detailed analysis of neutrino cooling effects in primordial hot regions, emphasizing their significance for black hole cluster temperatures.

Findings

Neutrino cooling is effective for temperatures above 3 MeV.

The mechanism operates across a wide range of parameters.

Primordial black hole clusters can retain hot regions due to neutrino cooling.

Abstract

We consider the temperature dynamics of hypothetical primordial hot areas in the Universe. Such areas can be produced by the primordial density inhomogeneities and can survive to the modern era, in particular due to primordial black hole (PBH) cluster of size $R \gtrsim 1$ pc and more. Here we concentrate on the neutrino cooling effect which is realized due to reactions of weak $p\leftrightarrow n$ transitions and $e^{\pm}$ annihilation. The given neutrino cooling mechanism is found to work in a wide range of parameters. For those parameters typical for PBH cluster considered, the cooling mechanism is quite valuable for the temperatures $T \gtrsim 3$ MeV.