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Igor Nikitin

Publications and source records attributed to Igor Nikitin.

18 recordsLinked to original sources
arXiv2023

New dark matter scenarios with low energy photons and neutrinos

In this paper, a cosmological model is considered, in which dark matter is emitted by T-symmetric quasi-black holes distributed over galaxies. Low energy photons and neutrinos are taken as candidates for dark matter particles. Photon case can be closed due to the suppression of electromagnetic waves by interstellar/intergalactic medium. For neutrinos, two scenarios are considered. In the first, light neutrinos pair to bosonic quasiparticles that form massive halos around galaxies. In the second, heavier sterile neutrinos form massive halos without pairing. At the observables level, both scenarios turn out to be equivalent to the standard LambdaCDM model. At the same time, the considered model possesses additional sources -- quasi-black holes -- that can produce the required number of neutrinos in addition to the Big Bang. This opens up additional possibilities for cosmological constructions. The matching of the model with early cosmology and ongoing neutrino experiments is discussed. In addition, the possibility of solving general cosmological problems, including horizon, flatness and cosmological constant problems, as well as Hubble tension, within the framework of the considered model, is discussed.

physics.gen-ph↗
arXiv2021

Galactic model with a phase transition from dark matter to dark energy

This work continues the construction of a recently proposed model of dark matter stars. In this model, dark matter quanta are sterile massless particles that are emitted from the central regions of the galaxy in the radial direction. As a result, at large distances $r$ from the center of the galaxy, the mass density of dark matter has the form $\rho \sim r^{-2}$, in contrast to the homogeneous model $\rho=Const$. In the cosmological context, the homogeneous model with massless particles corresponds to the radiation epoch of the expansion of the universe, while the proposed inhomogeneous model turns out to be equivalent to $\Lambda$CDM. In this paper, scenarios will be considered in which the radial emission of dark matter is brought into hydrostatic equilibrium with a uniform background. It is shown that solutions exist if the uniform background has an equation of state typical for dark energy. Thus, this model describes a phase transition from dark matter inside the galaxy to dark energy outside of it. The specific mechanism for such a transition could be Bose-Einstein condensation. In addition, the question of what happens if dark matter particles are not sterile, for example, are photons of the Standard Model, is considered.

physics.gen-ph↗
arXiv2021

On dark stars, Planck cores and the nature of dark matter

Dark stars are compact massive objects, described by Einstein gravitational field equations with matter. The type we consider possesses no event horizon, instead, there is a deep gravitational well with a very strong redshift factor. Observationally, dark stars can be identified with black holes. Inside dark stars, Planck density of matter is reached, Planck cores are formed, where the equations are modified by quantum gravity. In the paper, several models of dark stars with Planck cores are considered, resulting in the following hypothesis on the composition of dark matter. The galaxies are flooded with low-energetic radiation from the dark stars. The particle type can be photons and gravitons from the Standard Model, can also be a new type of massless particles. The model estimations show that the extremely large redshift factor $z\sim10^{49}$ and the emission wavelength $\lambda_0\sim10^{14}$m can be reached. The particles are not registered directly in the existing dark matter experiments. They come in a density sufficient to explain the observable rotation curves. The emission has a geometric dependence of density on radius $\rho\sim r^{-2}$, producing flat rotation curves. The distribution of sources also describes the deviations from the flat shape. The model provides a good fit of experimental rotation curves. Outbreaks caused by a fall of an external object on a dark star lead to emission wavelength shifted towards smaller values. The model estimations give the outbreak wavelength $\lambda\sim1$m compatible with fast radio bursts. The paper raises several principal questions. White holes with Planck core appear to be stable. Galactic rotation curves in the considered setup do not depend on the matter type. Inside the galaxy, dark matter can be of hot radial type. At cosmological distances, it can behave like the cold uniform type.

astro-ph.GA↗
arXiv2019

Quantum Gravity Wormholes and Topological Teleporter

The question of a possibility of opening a wormhole due to the deformation of the equation of state of the matter caused by quantum gravity effects is considered. As a wormhole environment, the previously considered model of a galaxy with radial flows of dark matter is selected. The calculation shows, that for a wormhole solution in the framework of this model, after the nominal classical density exceeds a critical value in the Planck range, the components of the energy-momentum tensor become negative in a certain order. First, the mass density becomes negative, then the radial pressure, then the tangential pressure. In this case, at some point the flare-out conditions necessary and sufficient to open the wormhole are fulfilled. Calculations are made to open a wormhole in a model with parameters of the Milky Way galaxy. It is shown that the opening of the wormhole is accompanied by a separation of the bubble of space, completely detached from the wormhole and the outer space. In addition to this solution, a topologically dual one is found, looking like an instant swapping of two volumes in space, which can be interpreted as an event of teleportation.

physics.gen-ph↗
arXiv2019

RDM-stars and related topics

In this paper, we will continue to study the model of black holes coupled to the radial flows of dark matter (RDM-stars). According to recent studies, this model well describes the experimental Rotation Curves (RCs) of spiral galaxies, also, RDM-stars can produce signals with the characteristics of Fast Radio Bursts (FRBs). In this paper, we will perform a combined analysis of experimental data on RCs and FRBs, which will allow to constrain tighter parameters of the model. We will also show that within the framework of the model, the Tully-Fisher relation with a slope of $ \beta = 3-4 $ can be obtained. Further, several particular solutions will be considered: tachyonic oven -- a solution in which the incoming flow of tachyons turns into an outgoing flow of massive particles; shell condensate -- a naked singularity of negative mass covered by a thin shell of positive mass, so that the Schwarzschild solution of negative mass inside is joined to one of positive mass outside; also, an RDM solution with a cosmological constant will be considered. Further, in the model under consideration, Penrose diagrams will be constructed, which share common features with Schwarzschild solutions of positive and negative mass, whose combination the model is. The mechanism of effective formation of negative masses in the model is discussed, which is activated when the density of the central core exceeds the Planck value, similarly to the previously studied quantum bounce effect.

astro-ph.GA↗
arXiv2019

RDM-stars and galactic rotation curves

The recently formulated model of black holes coupled to the radial flows of dark matter (RDM-stars) is considered and the shape of the galactic rotation curves predicted by the model is evaluated. Under the assumption that the density of black holes is proportional to the density of luminous matter, the model perfectly fits the experimental data, both for the universal rotation curve, describing the spiral galaxies of a general form, and for the grand rotation curve, describing the orbital velocities of Milky Way galaxy in a wide range of distances. The modeling of the galactic gravitational field at large distances from the center and out of the galactic plane is also discussed.

astro-ph.GA↗
arXiv2018

RDM-stars as sources of fast radio bursts

In this work we consider a recently formulated model of a black hole coupled with radially directed flows of dark matter (RDM-star). In this model, a cutoff by quantum gravity (QG) creates a core of Planck density, filled with a gas of Planck mass particles, inside the star. Further, in this model, a fast radio burst (FRB) can be generated via the following mechanism. An object of an asteroid mass falls onto an RDM-star. Due to large gravitational forces available in the interior, the RDM-star works as a powerful accelerator, boosting the nucleons composing the object to extremely high energies. Upon collision with the core, the nucleons enter in deeply inelastic reactions with the Planck particles composing the core. This process is followed by stimulated emission of highly energetic photons. On the way outside, these photons are subjected to a strong redshift factor, downscaling their frequencies to the radio diapason, as a result producing an FRB. A straightforward computation gives a characteristic upper FRB frequency of 0.6GHz. With attenuation factors, it is stretched to a range 0.35-8GHz, fitting well with the observable FRB frequencies. We also discuss the reconstruction of other FRB parameters in frames of the model.

gr-qc↗
arXiv2018

Stability of white holes revisited

It is shown that the models of white hole interacting with external matter can be made stable by introduction of a negative central mass. Similar results are obtained for the models of white hole, interacting with null shells, with radial flows of matter and with photon gas. In realistic models, a naked timelike singularity corresponding to the negative mass is hidden under a coat of positive mass, providing an extremely strong redshift for photons born in the Planck neighborhood of the singularity and observed at infinity, thereby realizing the principle of cosmic censorship in a relaxed form.

gr-qc↗
arXiv2017

Wormhole solutions of RDM model

The model of a spiral galaxy with radially directed flows of dark matter is extended by exotic matter, in a form of a perfect fluid with a linear anisotropic equation of state. The exotic matter is collected in the minimum of gravitational potential and opens a wormhole in the center of the galaxy. The flows of dark matter pass through the wormhole and form a mirror galaxy on the other side. The influence of model parameters to the shape of solution is studied, a solution matching parameters of Milky Way galaxy is computed.

gr-qc↗
arXiv2017

Static spherically symmetric solutions of Einstein field equations with radial dark matter

We study a static spherically symmetric problem with a black hole and radially directed geodesic flows of dark matter. The obtained solutions have the following properties. At large distances, the gravitational field produces constant velocities of circular motion, i.e., flat rotation curves. At smaller distances, the field switches to Newtonian regime, then to Schwarzschild regime. Deviations from Schwarzschild regime start below the gravitational radius. The dark matter prevents the creation of event horizon, instead, a spherical region possessing extremely large redshift is created. The structure of space-time for the obtained solutions is investigated and the implications for the models of the galaxies are discussed.

gr-qc↗
arXiv2016

Tachyonic models of dark matter

We consider a spherically symmetric stationary problem in General Relativity, including a black hole, inflow of normal and tachyonic matter and outflow of tachyonic matter. Computations in a weak field limit show that the resulting concentration of matter around the black hole leads to gravitational effects equivalent to those associated with dark matter halo. In particular, the model reproduces asymptotically constant galactic rotation curves, if the tachyonic flows of the central supermassive black hole in the galaxy are considered as a main contribution.

gr-qc↗
arXiv2015

Statistical analysis of narrow-band signals at setilive.org

SETILive is a web project forwarding radio signals from SETI Institute's Allen Telescope Array (ATA) for the analysis of volunteers. It contains a large archive with more than 1.5 millions observations for more than 7.5 thousands observation targets, including directions to exoplanets discovered by telescope Kepler and other sources. It also supports various tools for signal collection and classification. Till recent time it supported live feeds of signals from ATA together with a feedback loop, a possibility to interrupt the schedule and repeat the observation of an interesting signal registered by sufficiently many viewers. Unfortunately, since 12-Oct-2014 the live feeds have been discontinued. We hope that the project will persist, taking into account the importance of the search subject, the worldwide interest to the topic and the value of already collected data. In this paper we present the results of statistical analysis of data stored in SETILive archive, using Radon transform and specially constructed filter for selection of single beams, potential signals of ET origination. We will also estimate statistical significance of signals depending on their signal-to-noise ratio using Monte Carlo simulation and select 28 strong signals and totally 1072 statistically significant signals in the archive.

astro-ph.IM↗
arXiv2004

Quantization of Non-Critical Bosonic Open String Theory

The theory of relativistic strings is considered in frames of Hamiltonian formalism and Dirac's quantization procedure. A special gauge fixing condition is formulated, related with the world sheet of the string in Lorentz-invariant way. As a result, a new set of Lorentz-invariant canonical variables is constructed, in which a consistent quantization of bosonic open string theory could be done in Minkowski space-time of dimension $d=4$. The obtained quantum theory possesses spin-mass spectrum with Regge-like behavior.

hep-th↗
arXiv2003

String theory in Lorentz-invariant light cone gauge - II

We perform a quantization of 4-dimensional Nambu-Goto theory of open string in light cone gauge, related in Lorentz-invariant way with the world sheet. This allows to obtain a quantum theory without anomalies in Lorentz group. We consider a special type of gauge fixing conditions, imposed in oscillator sector of the theory, which lead to a relatively simple Hamiltonian mechanics, convenient for canonical quantization. We discuss the algebraic and geometric properties of this mechanics and determine its mass spectrum for the states of spin singlet S=0.

hep-th↗
arXiv2003

String theory in Lorentz-invariant light cone gauge - III

This paper completes the work, initiated in [hep-th/9906003,hep-th/0301204], further referred as Parts I and II, concerning to Dirac's quantization of Nambu-Goto theory of open string, formulated in the space-time of dimension d=4. Here we perform more detailed study of Gribov's copies in the classical mechanics and determine the quantum spectrum of masses for the arbitrary spin case.

hep-th↗
arXiv2001

Structure of singularities on the world sheets of relativistic strings

We show that relativistic strings of open and closed types in Minkowski space-time of dimension 3 and 4 have topologically stable singular points. This paper describes the structure of singularities, derives their normal forms, and introduces a local characteristic of singularity (topological charge), possessing a global law of conservation. Two other types of solutions (breaking and exotic strings) are also considered, which have singularities at arbitrary value of dimension.

hep-th↗
arXiv1999

Exotic solutions in string theory

Solutions of classical string theory, correspondent to the world sheets, mapped in Minkowsky space with a fold, are considered. Typical processes for them are creation of strings from vacuum, their recombination and annihilation. These solutions violate positiveness of square of mass and Regge condition. In quantum string theory these solutions correspond to physical states |DDF>+|sp> with non-zero spurious component.

hep-th↗