arXiv subjects

A. A. Kirillov

Publications and source records attributed to A. A. Kirillov.

At least 19 recordsLinked to original sources

arXiv2025

Interaction of domain walls with scalar particles in the early Universe

The formation of solitons (such as closed domain walls) in the super-Early Universe is predicted in a number of theories of the formation of primordial black holes. However, the interaction of particles of the surrounding medium with the solitons should affect their dynamics. In the paper, we consider the interaction between domain walls and scalar particles which can play a role of dark matter. It is shown that when the temperature of the scalar particle gas, caused by the expansion of the Universe, decreases below a certain threshold value, the wall abruptly becomes opaque and locks particles inside itself. We discuss the dynamics of a single domain wall taking into account pressure of scalar particles locked inside a closed wall. It is shown, this effect leads to a time delay of domain wall collapse and the deferred formation of primordial black holes.

gr-qc↗

arXiv2025

Soliton foam formation in the early Universe

The formation of composite solitons produced by scalar fields without thermal phase transitions in the early Universe is considered. We present numerical simulations of the formation and evolution of soliton structures at the post-inflationary stage. The realistic initial conditions are obtained through the simulation of multiple quantum fluctuations during the inflation epoch. The initial field distributions allow to form local soliton clusters in the early Universe without the need for the thermal production of a soliton network throughout the Universe. We find that in three-dimensional space, the nontrivial composite field structures are formed in the form of < >, consisting of closed domain walls, domain walls bounded by cosmic strings, and scalar field radiation. The possible cosmological implications of the soliton foam are discussed.

hep-th↗

arXiv2024

Application of Machine Learning Methods for Detecting Atypical Structures in Astronomical Maps

The paper explores the use of various machine learning methods to search for heterogeneous or atypical structures on astronomical maps. The study was conducted on the maps of the cosmic microwave background radiation from the Planck mission obtained at various frequencies. The algorithm used found a number of atypical anomalous structures in the actual maps of the Planck mission. This paper details the machine learning model used and the algorithm for detecting anomalous structures. A map of the position of such objects has been compiled. The results were compared with known astrophysical processes or objects. Future research involves expanding the dataset and applying various algorithms to improve the detection and classification of outliers.

astro-ph.IM↗

arXiv2024

Possible scenario of relic wormhole formation

It is shown that in the presence of virtual wormholes, the vacuum is unstable, which leads to a series of phase transitions in the early Universe. Then the standard Kibble scenario predicts the formation of defects such as domain walls. An unusual feature of virtual wormholes is that they generate defects with negative energy density. Such defects have macroscopic dimensions and can support the necks of already real primary wormholes, which gives reason to consider relic wormholes as realistic astrophysical objects.

gr-qc↗

arXiv2024

On properties of the distribution of virtual wormholes in a vacuum

A model of space-time foam in the form of an arbitrary distribution of spherical Euclidean wormholes is considered. A method for constructing the exact solution of Einstein's Euclidean equations for the metric corresponding to this model is proposed. In the framework of our model we obtain the expression for the Euclidean action and its dependence on the parameters of wormholes in the explicit form. It is shown how the solutions obtained make it possible to determine all possible correlation functions associated with the parameters of virtual wormholes in the vacuum state.

gr-qc↗

arXiv2021

Cosmological Formation of (2+1)-Dimensional Soliton Structures in Models Possessing Potentials with Local Peaks

Production of domain walls and string-like solitons in the model with two real scalar fields and potential with at least one saddle point and a local maximum is considered. The model is regarded as 2-dimensional spatial slices of 3-dimensional entire structures. It is shown that, in the early Universe, both types of solitons may appear. In addition, the qualitative estimate of the domain walls and strings formation probabilities is presented. It is found that the probability of the formation of string-like solitons is suppressed compared to that of domain walls.

hep-th↗

arXiv2021

Evolution of the cluster of primordial black holes within the Fokker-Planck approach

The calculation results of the evolution of the cluster of primordial black holes based on the Fokker-Planck equation with neglecting of the gas accretion onto black holes are presented. In addition, we consider how a massive black hole located within the cluster center affects on its evolution. Despite it creates an additional potential in the central region of the cluster and might capture surrounding black holes, a negligible growth rate of a central black hole was shown for 1 Gyr. Furthermore, we find a significant (approximately tenfold) expansion of the cluster.

astro-ph.CO↗

arXiv2020

Scattering of GWs on wormholes: foreshadow and afterglow/echoes from binary merges

We study specific features of the scattering of gravitational waves on wormholes and normal matter objects. We derive and solve the GW energy transport equation and show that the scattered signal lies in the same frequency spectrum bands as the basic signal. The scattering forms specific long living tails which always accompany the basic signal and have a universal form. The scattering on normal matter objects forms tails which have always the retarding character, while wormholes lead to advanced tails as well. In addition, wormholes may produce considerably stronger effect, when the total energy in tails exceeds the energy of the incident wave by the factor up to $10^{3}$ . In both cases the retarding tails have a long living character when the mean amplitude behaves with time as $h\sim 1/\sqrt{t+R/c}$. For a single GW event the echo tails give only a tiny contribution to the mean amplitude. However such tails accumulate with events and may be observed by their contribution to the noise produced by the stochastic GW background.

gr-qc↗

arXiv2020

Possible formation of ring galaxies by torus-shaped magnetic wormholes

We present the hypothesis that some of ring galaxies were formed by relic magnetic torus - shaped wormholes. In the primordial plasma before the recombination magnetic fields of wormholes trap baryons whose energy is smaller than a threshold energy. They work as the Maxwell's demons collecting baryons from the nearest (horizon size) region and thus forming clumps of baryonic matter which have the same torus-like shapes as wormhole throats. Such clumps may serve as seeds for the formation of ring galaxies and smaller objects having the ring form. Upon the recombination torus-like clumps may decay and merge. Unlike galaxies, such objects may contain less or even no dark matter in halos. However the most stringent feature of such objects is the presence of a large - scale toroidal magnetic field. We show that there are threshold values of magnetic fields which give the upper and lower boundary values for the baryon clumps in such protogalaxies.

gr-qc↗

arXiv2018

On distortion of the background radiation spectrum by wormholes: kinematic Sunyaev-Zel'dovich effect

The problem of scattering of the background radiation on relic cosmological wormholes is considered. It is shown that static wormholes do not perturb the spectrum at all. The presence of peculiar velocities of wormholes results in a distortion of the CMB spectrum which is analogous to the kinematic Sunyaev-Zel'dovich effect. In the first order in $v/c$ the distortion of CMB cannot be separated from from the Compton scattering on electrons. In next orders the scattering on wormholes exhibits some difference from the Compton scattering. High-energy cosmic-ray particles spectrum does not change the form by KSZ, but undergoes a common Doppler shift. Such features may give a new tool to detect the presence of relic wormholes in our Universe.

gr-qc↗

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

On scattering of CMB radiation on wormholes: kinetic SZ-effect

The problem of scattering of CMB radiation on wormholes is considered. It is shown that a static gas of wormholes does not perturb the spectrum of CMB. In the first order by $v/c$ the presence of peculiar velocities gives rise to the dipole contribution in $ΔT/T$, which corresponds to the well-known kinetic Sunyaev-Zel'dovich effect. In next orders there appears a more complicated dependence of the perturbed CMB spectrum on peculiar velocities. We also discuss some peculiar features of the scattering on a single wormhole.

gr-qc↗

arXiv2015

Cosmological wormholes

We describe in details the procedure how the Lobachevsky space can be factorized to a space of the constant negative curvature filled with a gas of wormholes. We show that such wormholes have throat sections in the form of tori and are traversable and stable in the cosmological context. The relation of such wormholes to the dark matter phenomenon is briefly described. We also discuss the possibility of the existence of analogous factorizations for all types of homogeneous spaces.

gr-qc↗

arXiv2015

Effective action for a free scalar field in the presence of spacetime foam

We model spacetime foam by a gas of virtual wormholes. For a free scalar field we derive the effective Lagrangian which accounts for the interaction with spacetime foam and contains two additional non-local terms. One term describes the scattering of scalar particles on virtual wormholes and explicitly reproduces the Pauli-Villars regularization procedure. The second term describes the back reaction of particles on the number density of wormholes and introduces a self-interaction between particles.

gr-qc↗

arXiv2015

Origin of the logarithmic correction to the Newton's law in the presence of a homogeneous gas of wormholes

We suggest a new scenario in which the Universe starts its evolution with a fractal topological structure. This structure is described by a gas of wormholes. It is shown that the polarization of such a gas in external fields possesses a spatial dispersion, which results in a modification of the Newton's law. The dependence on scales is determined by the distribution of distances between throat ends. The observed in galaxies logarithmic correction confirms that the distribution has fractal properties. We also discus the possibility of restoring such a distribution from observations.

gr-qc↗

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↗