arXiv subjects

K. M. Belotsky

Publications and source records attributed to K. M. Belotsky.

At least 19 recordsLinked to original sources

arXiv2026

Microlensing by Cluster of Primordial Black Holes

Numerous microlensing survey programs have constrained the possibility of dark matter existing in the form of compact objects within the Galactic halo. These constraints on the dark matter fraction were derived under the assumption of isolated, widely separated objects. This work investigates microlensing by primordial black holes (PBHs) organized into clusters. In this scenario, it is necessary to account for both the influence of neighboring PBHs and the collective gravitational potential of the entire cluster, which significantly complicates the microlensing light curve. Events exhibiting such complex light curves elude detection in observational experiments such as MACHO, EROS, OGLE, POINT-AGAPE, and HSC. It is demonstrated that a significant fraction of PBH dark matter (up to 93\% for the models studied) remains undetected in these observational data. However, for all considered cluster models, a substantial population of PBHs still behaves as isolated lenses. Consequently, the clustering of PBHs does not completely eliminate the microlensing constraints on the PBH contribution to dark matter.

astro-ph.CO↗

arXiv2025

Reconstruction of the dark matter density profile from cosmic positron anomaly data

In this work we continue our investigations of the possibility of explanation of the positron anomaly (PA) in cosmic rays with the help of annihilating or decaying dark matter (DM) component by varying its space distribution. In the contrast of our previous studies, where we first assumed some specific spatial distribution of DM component and looked at how it agrees with data, here we solve, in some sense, the inverse problem: we search for distribution, in a mathematical way, which satisfies observational data. A unique algorithm has been implemented which, using linear algebra and adaptive grid methods, adjusts distribution to the data. It allows telling in principle whether or not is possible to solve PA problem by variation of spatial distribution of DM sources. A positive result has been formally obtained. A class of solutions can be identified. Though the distributions obtained at the chosen injection spectra may seem slightly realistic, nonetheless it demonstrates a quite powerful possibility in explaining PA that could be realized in more realistic models.

astro-ph.HE↗

arXiv2022

Hot primordial regions with anomalous hydrogenless chemical composition

We study primordial nucleosynthesis in hypothetical hot regions that could be formed by the primordial density inhomogeneities. It is shown that the regions survived up to the present times acquire an abnormally high metallicity. This conclusion holds in wide range of initial parameters of such regions. We considered the thermonuclear reaction rates and estimated abundances of deuterium and helium-3 and -4 inside these areas. It has been established that all baryons tend to form helium-4, which is the thermonuclear link in the chain of formation of heavier elements.

astro-ph.CO↗

arXiv2020

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

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.

astro-ph.CO↗

arXiv2020

Consideration of a loop decay of dark matter particle into electron-positron from point of view of possible FSR suppression

Cosmic positron anomaly is still not explained. Explanation with dark matter (DM) decay or annihilation is one of the main attempts to do it. But they suffer with shortcoming as overproduction of induced gamma-radiation which contradict to cosmic gamma-background. Final state radiation (FSR) in such processes is supposed under standard conditions (by default) to have the basic contribution in it. Our group elaborates possibility to evade this problem in different ways. Here we continue one of them connected with possibility of suppression of FSR due to specifics of Lagrangian describing DM particle decay. Loop through two new spinors and scalar is considered. Effect of FSR suppression is found to be existing but at the very low level in the considered case.

hep-ph↗

arXiv2020

The "Dark disk" model in the light of DAMPE experiment

There are a lot of models considering the Dark Matter (DM) to be the origin of cosmic ray (CR) positron excess. However, they face an obstacle in the form of gamma-rays. Simple DM models tend to overproduce gamma-rays, leading to contradiction with isotropic gamma-ray background (IGRB). The < > model has been proposed to alleviate this contradiction. This work considers results of DAMPE experiment in the framework of the disk model. It is obtained that such a framework allows improving data fit considerably.

astro-ph.HE↗

arXiv2020

Theoretical indication of a possible asymmetry in gamma-radiation between Andromeda halo hemispheres due to Compton scattering on electrons from their hypothetical sources in the halo

Dark matter (DM) can give observable effects decaying or annihilating with production of electrons or/and photons. Such probability was widely researched for our Galaxy. Here we consider one aspect of similar effect for Andromeda galaxy. We explicitly estimate the energy of the photon of the medium experiencing Inverse Compton (IC) scattering off electron in halo. These photons can be registered by different experiments. Dark matter annihilation or decay could be the source of high energy electrons in halo, though the source could be of other origins too (e.g. running neutron stars). Because of specifics in space orientation of Andromeda galaxy disk (a little inclined to the line of sight), the difference in energies could arise for the photons from two hemispheres of Andromeda halo. It is obtained that such asymmetry can be at the level of several 10%.

astro-ph.HE↗

arXiv2020

Neutrino Cooling of Primordial Hot Regions

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.

astro-ph.CO↗

arXiv2019

Indirect effects of dark matter

Here we briefly review possible indirect effects of dark matter (DM) of the Universe. It includes effects in cosmic rays (CR): first of all, the positron excess at $\sim$ 500 GeV and possible electron-positron excess at 1-1.5 TeV. We tell that the main and least model-dependent constraint on such possible interpretation of CR effects goes from gamma-ray background. Even ordinary $e^+e^-$ mode of DM decay or annihilation produces prompt photons (FSR) so much that leads to contradiction with data on cosmic gamma-rays. We present our attempts to possibly avoid gamma-ray constraint. They concern peculiarities of both space distribution of DM and their physics. The latter involves complications of decay/annihilation modes of DM, modifications of Lagrangian of DM-ordinary matter interaction, and inclusion of mode with identical fermions in final state. In this way, no possibilities to suppress were found except, possibly, mode with identical fermions. While the case of spatial distribution variation allows achieving consistency between different data. Also we consider stable form of dark matter which can interact with baryons. We show which constraint such DM candidate can get from damping effect in plasma during large scale structure formation in comparison with other existing constraints.

hep-ph↗

arXiv2019

Analysis of programming tools in framework of dark matter physics and concept of new MC-generator

We analyse here some programming tools (MC-generators) from viewpoint of their application to the tasks of dark matter (DM) interpretation of cosmic rays puzzles. We shortly describe our tasks, where the main goal is the solution of the problem of suppression of gamma-rays induced by the products of DM decay or annihilation in Galaxy. We show that existing MC-generators do not fully satisfy our task, comparing them, and suggest our own one.

hep-ph↗

arXiv2018

Development of dark disk model of positron anomaly origin

Dark disk model could be a remedy for dark matter (DM) explanation of positron anomaly (PA) in cosmic rays (CR). The main difficulty in PA explanation relates to cosmic gamma-radiation which is inevitably produced in DM annihilation or decay leading to tension with respective observation data. Introduction of "active" (producing CR) DM component concentrating in galactic disk alleviates this tension. Earlier we considered two-lepton modes, with branching ratios being chosen to fit in the best way all the observation data. Here we considered, in framework of the same dark disk model, two cases: two-body final state annihilation and four-body one, and in each case a quark mode is added to the leptonic ones. It is shown that 4-body mode case is a little better than 2-body one from viewpoint of quality of observation data description at the fixed all other parameters (of CR propagation, background, disk height). The values of DM particle mass around 350 GeV and 500 GeV are more favourable for 2- and 4-body modes respectively. Higher values would improve description of data on positrons only but accounting for data on gamma-radiation prevents it because of unwanted more abundant high-energy gamma production. Inclusion of the quark modes improves a little fitting data in both 4- and 2-body mode cases, contrary to naive expectations. In fact, quark mode has a bigger gammas yield than that of most gamma-productive leptonic mode~--- tau, but they are softer due to bigger final state hadron multiplicity.

astro-ph.HE↗

arXiv2017

Reionization effect enhancement due to primordial black holes

Primordial black holes (PBH) could account for variety of phenomena like dark matter, reionization of the Universe, early quasars, coalescence of black holes registered through gravitational waves recently. Each phenomenon relates to PBH of a specific mass range. PBH mass spectra varies in a wide range depending on specific model. Earlier we have shown that PBH with monochromatic mass distribution around $5\times 10^{16}$ g value allow to re-ionize the Universe moderately. Here we show that reionization effect and contribution to dark matter can be simultaneously enhanced with more natural extended mass distribution in the range around the same mass value.

astro-ph.CO↗

arXiv2016

On the classical description of the recombination of dark matter particles with a Coulomb-like interaction

Cold dark matter (DM) scenario may be cured of several problems by involving self-interaction of dark matter. Viability of the models of long-range interacting DM crucially depends on the effectiveness of recombination of the DM particles, making thereby their interaction short-range. Usually in numeric calculations, recombination is described by cross section obtained on a feasible quantum level. However in a wide range of parameter values, a classical treatment, where the particles are bound due to dipole radiation, is applicable. The cross sections, obtained in both approaches, are very different and lead to diverse consequences. Classical cross section has a steeper dependence on relative velocity, what leads to the fact that, after decoupling of DM particles from thermal background of "dark photons" (carriers of DM long-range interaction), recombination process does not "freeze out", diminishing gradually density of unbound DM particles. Our simplified estimates show, that at the taken parameter values (the mass of DM particle is $100$ GeV, interaction constant is $100^{-1}$, and quite natural assumptions on initial conditions, from which the result is very weakly dependent) the difference in residual density reaches about $5$ orders of magnitude on pre-galactic stage. This estimate takes into account thermal effects induced by dipole radiation and recombination, which resulted in the increase of both temperature and density of DM particles by a half order of magnitude.

astro-ph.CO↗

arXiv2015

Primordial black holes with mass $10^{16}-10^{17}$ g and reionization of the Universe

Primordial black holes (PBHs) with mass $10^{16}-10^{17}$ 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 $e^{\pm}$-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 $z\sim 5... 10$. 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 50-100% by $z\sim 5$ for PBH mass $(3...7)\times 10^{16}$ g with their abundance corresponding to the upper limit.

astro-ph.CO↗

arXiv2014

Signatures of primordial black hole dark matter

The nonbaryonic dark matter of the Universe is assumed to consist of new stable forms of matter. Their stability reflects symmetry of micro world and mechanisms of its symmetry breaking. In the early Universe heavy metastable particles can dominate, leaving primordial black holes (PBHs) after their decay, as well as the structure of particle symmetry breaking gives rise to cosmological phase transitions, from which massive black holes and/or their clusters can originate. PBHs can be formed in such transitions within a narrow interval of masses about $10^{17}$g and, avoiding severe observational constraints on PBHs, can be a candidate for the dominant form of dark matter. PBHs in this range of mass can give solution of the problem of reionization in the Universe at the redshift $z\sim 5... 10$. Clusters of massive PBHs can serve as a nonlinear seeds for galaxy formation, while PBHs evaporating in such clusters can provide an interesting interpretation for the observations of point-like gamma-ray sources. Analysis of possible PBH signatures represents a universal probe for super-high energy physics in the early Universe in studies of indirect effects of the dark matter.

astro-ph.CO↗

arXiv2012

Gamma-ray evidences of the dark matter clumps

We discuss the possibility of identification of point-like gamma-ray sources (PGS) with small scale dark matter (DM) clumps in our Galaxy. Gamma-rays are supposed to originate from annihilation of DM particles in the clumps, where annihilation rate is supposed to be enhanced, besides higher density, due to smaller relative velocities $v$ of DM particles. We parameterized the annihilation cross section $σ_\text{ann}(v)$ in the form of an arbitrary power law dependence on the relative velocity $v$ with/without factor of Sommerfeld-Gamow-Sakharov, implying existence of a new Coulomb-like interaction. Adopting different parameters of cross section and clump, satisfying condition $Ω\lesssim 0.2$ on density of DM particles of question, they are constrained from comparison with Fermi/LAT data on unidentified PGS as well as on diffuse $γ$-radiation; results are applied to concrete DM candidates. Such analysis is found to be sensitive enough to existing uncertainty in the density profiles of DM in the clump what can provide a tool for their test. Also we discuss possibilities when gamma-radiating clump changes visibly its position on celestial sphere and it is seen as a spatially extended gamma-source (EGS), what can be probed in future experiments like Gamma-400.

astro-ph.HE↗

arXiv2012

Clusters of Black Holes as Point-Like Gamma-ray Sources

The possibility of identifying some of Galactic gamma-ray sources as clusters of primordial black holes is discussed. The known scenarios of supermassive black hole formation indicate the multiple formation of lower-mass black holes. Our analysis demonstrates that due to Hawking evaporation the cluster of black holes with masses about $10^{15}$ g could be observed as a gamma-ray source. The total mass of typical cluster is $\sim 10 M_\odot$. Detailed calculations have been performed on the basis of specific model of primordial black hole formation.

astro-ph.HE↗

arXiv2006

Composite Dark Matter and its Charged Constituents

Stable charged heavy leptons and quarks can exist and hide in elusive atoms, bound by Coulomb attraction and playing the role of dark matter. However, in the expanding Universe it is not possible to recombine all the charged particles into such atoms, and the positively charged particles, which escape this recombination, bind with electrons in atoms of anomalous isotopes with pregalactic abundance, exceeding substantially the terrestrial upper limits. This abundance can not be reduced in the dense matter bodies, if negatively charged particles have charge -1. Therefore composite dark matter can involve only negatively charged particles with charge -2, while stable heavy particles with charge -1 should be excluded. Realistic scenarios of composite dark matter, avoiding this problem of anomalous isotope over-production, inevitably predict the existence of primordial "atoms", in which primordial helium traps all the free negatively charged heavy constituents with charge -2. Study of the possibility for such primordial heavy $α$ particle with compensated charge to exist as well as the search for the stable charged constituents in cosmic rays and accelerators provide crucial test for composite dark matter scenarios.

astro-ph↗