Neutrino Cooling of Primordial Hot Regions

TL;DR

This paper investigates how neutrino cooling affects primordial hot regions with density inhomogeneities, showing that such regions cool down to about 10 keV through nuclear reactions involving neutron-proton transitions.

Contribution

It introduces a model of neutrino cooling in primordial hot regions and estimates the final temperature considering nuclear reaction thresholds and particle densities.

Findings

Final temperature of hot regions is approximately 10 keV.

Cooling is driven by nuclear reactions with n-p transitions.

Reaction rates are suppressed by threshold effects and particle density diminishment.

Abstract

The effect of neutrino cooling of possible primary regions filled by the hot matter is discussed. Such regions could contain the primordial density inhomogeneities of different origin and survive up to modern epoch. We show that the final temperature of such region is $\sim 10\, {\rm keV}$ provided that the initial temperature is within the interval $10\, {\rm keV} ... 100\, {\rm MeV}$. The cooling is realized due to the nuclear reactions containing $n-p$ transition. The lower limit $10\, {\rm keV}$ is accounted for by suppression of the reactions rates because of threshold effect and $n$, $e^{\pm}$ density diminishment.