Primordial black holes with mass 10{sup 16}−10{sup 17} g and reionization of the Universe
Abstract
Primordial black holes (PBHs) with mass 10{sup 16}−10{sup 17} g almost escape constraints from observations so could essentially contribute to dark matter density. Hawking evaporation of such PBHs produces with a steady rate γ and e{sup ±}radiations in MeV energy range, which can be absorbed by ordinary matter. Simplified estimates show that a small fraction of evaporated energy had to be absorbed by baryonic matter what can turn out to be enough to heat the matter so it is fully ionized at the redshift z∼ 5... 10. The result is found to be close to a borderline case where the effect appears, what makes it sensitive to the approximation used. In our approximation, degree of gas ionization reaches 50100% by z∼ 5 for PBH mass (3...7)× 10{sup 16} g with their abundance corresponding to the upper limit.
 Authors:
 National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation)
 Publication Date:
 OSTI Identifier:
 22382009
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2015; Journal Issue: 01; Other Information: Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; APPROXIMATIONS; BARYONS; BLACK HOLES; DENSITY; EVAPORATION; HEAT; LIMITING VALUES; MASS; MEV RANGE; NONLUMINOUS MATTER; RED SHIFT; UNIVERSE
Citation Formats
Belotsky, K.M., and Kirillov, A.A., Email: kbelotsky@yandex.ru, Email: kirillovaa@yandex.ru. Primordial black holes with mass 10{sup 16}−10{sup 17} g and reionization of the Universe. United States: N. p., 2015.
Web. doi:10.1088/14757516/2015/01/041.
Belotsky, K.M., & Kirillov, A.A., Email: kbelotsky@yandex.ru, Email: kirillovaa@yandex.ru. Primordial black holes with mass 10{sup 16}−10{sup 17} g and reionization of the Universe. United States. doi:10.1088/14757516/2015/01/041.
Belotsky, K.M., and Kirillov, A.A., Email: kbelotsky@yandex.ru, Email: kirillovaa@yandex.ru. 2015.
"Primordial black holes with mass 10{sup 16}−10{sup 17} g and reionization of the Universe". United States.
doi:10.1088/14757516/2015/01/041.
@article{osti_22382009,
title = {Primordial black holes with mass 10{sup 16}−10{sup 17} g and reionization of the Universe},
author = {Belotsky, K.M. and Kirillov, A.A., Email: kbelotsky@yandex.ru, Email: kirillovaa@yandex.ru},
abstractNote = {Primordial black holes (PBHs) with mass 10{sup 16}−10{sup 17} g almost escape constraints from observations so could essentially contribute to dark matter density. Hawking evaporation of such PBHs produces with a steady rate γ and e{sup ±}radiations in MeV energy range, which can be absorbed by ordinary matter. Simplified estimates show that a small fraction of evaporated energy had to be absorbed by baryonic matter what can turn out to be enough to heat the matter so it is fully ionized at the redshift z∼ 5... 10. The result is found to be close to a borderline case where the effect appears, what makes it sensitive to the approximation used. In our approximation, degree of gas ionization reaches 50100% by z∼ 5 for PBH mass (3...7)× 10{sup 16} g with their abundance corresponding to the upper limit.},
doi = {10.1088/14757516/2015/01/041},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 01,
volume = 2015,
place = {United States},
year = 2015,
month = 1
}

The mass spectrum of primordial black holes formed in a universe with maximally hard equation of state of matter is calculated with allowance for the influence of smallscale inhomogeneities on the dynamical development of large scale perturbations. The basic object of investigation is the field of initial deviations of the density, which are characterized by a normal distribution and standard deviation approximated by a power function of the reciprocal of the mass. It is shown that for a flat spectrum of initial perturbations of the metric the mass distribution function of the primordial black holes has a clear maximum. Themore »

Clusters of primordial black holes and reionization problem
Clusters of primordial black holes may cause the formation of quasars in the early Universe. In turn, radiation from these quasars may lead to the reionization of the Universe. However, the evaporation of primordial black holes via Hawking’s mechanism may also contribute to the ionization of matter. The possibility of matter ionization via the evaporation of primordial black holes with allowance for existing constraints on their density is discussed. The contribution to ionization from the evaporation of primordial black holes characterized by their preset mass spectrum can roughly be estimated at about 10{sup −3}. 
Formation of primordial black holes in a ''stiff'' universe
In the context of a stiff universe, the formation of primordial black holes from adiabatic perturbations is discussed with allowance for their reverse influence on the expansion dynamics. In a selfconsistent treatment, highfrequency perturbations will effectively renormalize the equation of state, diminishing the Jeans length and precluding the development of a catastrophic accretion regime. When dissipation of finescale irregularities is taken into account, the results qualitatively remain the same, but one can relate the minimum mass of a black hole newly formed in a stiff universe to the value of the specific entropy. 
Primordial black holes and the era of superheavyparticle dominance in the early universe
In the context of grand unified theories of elementary particles, an era is predicted to have existed in the early universe during which superheavy nonrelativistic particles predominated. The minimum probability of primordial black hole formation during this stage is estimated and compared with astrophysical upper limits on the PBH density so as to impose constraints on the unified theories. 
Comment on ''radiation accretion by primordial black holes in the early universe''
A model recently proposed by Hacyan for primordial black hole (PBH) growth in the early universe is extended to a class of equations of state p=a/sub s//sup 2/epsilon (p = pressure, a/sub s//sup 2/ = constant sound speed epsilon=energy density) and to arbitrary time delay between the births of the universe and of the PBH. We show that the PBH mass grows asymptotically in proportion to the horizon mass of the background for all a/sub s/, and that the generalrelativistic matching to a flat background demands that the ingoing Vaidya metric used to model the PBH be selfsimilar. We emphasizemore »