arXiv subjects

V. M. Chechetkin

Publications and source records attributed to V. M. Chechetkin.

At least 19 recordsLinked to original sources

arXiv2026

The stability of voids in the Local Universe: The role of the cosmological constant

The Vlasov kinetic formalism is employed to study the evolution and stability of cosmic voids in the Local Universe, taking into account not only the gravitational attraction, but also the repulsive effect of the cosmological constant (i.e., local dark energy). In accordance with the theorem on the general function of the identity between the gravitational fields of a sphere and a point mass, the cosmological constant provides a natural explanation for the Hubble tension, attributing it to local and global flows characterized by different Hubble parameters. The crucial role of the Λ-repulsion in maintaining the stability of voids at the present epoch is demonstrated when Landau damping suppresses discrete collapse modes and prevents random local density perturbations inside the voids from growing and incorporating new galaxies into the walls. Inside the voids, the Λ-repulsion exceeds the attractive force of the residual matter, driving matter outward and accelerating its migration toward the void boundaries. In the Local (late) Universe, cosmic voids have entered a stage characterized by stable and more pronounced walls, as studied via observational surveys across different redshift ranges.

astro-ph.CO↗

arXiv2025

Cosmic voids and the kinetic analysis. V. Hubble tension, the cosmological constant and aperiodic filaments

We study the appearance and specific properties of the structures in the local Universe by means of the Vlasov kinetic technique. We consider the role of the cosmological constant in local structure formation via the theorem on the general function that satisfies the identity of the gravity of the sphere and of the point mass. Then, the Hubble tension is naturally explained as a result of two flows, a local and a global one, with non-coinciding Hubble parameters. The linearized Vlasov-Poisson equation with the cosmological term is shown to lead to van Kampen's waves, Landau damping, and then to aperiodic structures. Aperiodicity thereby emerges as a intrinsic feature of the filamentary and void structure of the local Universe, and reveals the self-consistent field mechanism of its formation. The damping of the aperiodicity is then predicted and can be observationally traced upon the increase in the scale of the filaments.

astro-ph.CO↗

arXiv2025

Cosmic voids and the kinetic analysis. IV. Hubble tension and the cosmological constant

The formation of the cosmic structures in the late Universe is considered using Vlasov kinetic approach. The crucial point is the use of the gravitational potential with repulsive term of the cosmological constant which provides a solution to the Hubble tension, that is the Hubble parameter for the late Universe has to differ from its global cosmological value. This also provides a mechanism of formation of stationary semi-periodic gravitating structures of voids and walls, so that the cosmological constant has a role of the scaling and hence can be compared with the observational data for given regions. The considered mechanism of the structure formation in late cosmological epoch then is succeeding the epoch described by the evolution of primordial density fluctuations.

gr-qc↗

arXiv2023

Cosmic voids and the kinetic analysis. III. Hubble tension and structure formation in the late Universe

We study structure formation in the late Universe within the Vlasov kinetic self-consistent field approach. Our work is principally focused on the use of the modified gravitational potential with a repulsive term of the cosmological constant, which is directly linked to observations that enable characterizations of the Hubble tension as the result of local and global flows. We formulate the criteria for the formation of the semi-periodic gravitating structures, along with the predictions of their quantitative scales associated with observable parameters. Our principal conclusion is that filament formation in the Local (late) Universe can proceed as a deterministic process that is distinct from the structures at larger scales that result from the essentially stochastic dynamics of density perturbations.

astro-ph.CO↗

arXiv2023

Cosmic voids and the kinetic analysis. II. Link to Hubble tension

We consider a principal problem, that of the possible dominating role of self-consistent gravitational interaction in the formation of cosmic structures: voids and their walls in the local Universe. It is in the context of the Hubble tension as a possible indication of the difference in the descriptions of the late (local) and early (global) Universe. The kinetic Vlasov treatment enables us to consider the evolution of gravitating structures where the fundamental role has the modified gravitational potential with a cosmological constant, leading to the prediction of a local flow with a Hubble parameter that is nonidentical to that of the global Hubble flow. The Poisson equation for a potential with an additional repulsive term, including an integral equation formulation, is analyzed, and we predict the appearance of multiply connected two-dimensional gravitating structures and voids in the local Universe. The obvious consequence of the developed mechanism is that the cosmological constant poses a natural scaling for the voids, along with the physical parameters of their local environment, which can be traced in observational surveys.

astro-ph.CO↗

arXiv2022

Cosmic voids and the kinetic analysis

The kinetic approach to the formation of the filaments in the large-scale matter distribution in the Universe is considered within the Vlasov formalism. The structures arise due to the self-consistent dynamics, along with the repulsive term in the modified Newtonian gravity which includes the cosmological constant. That modified gravity enables one to describe the Hubble tension as a result of two flows, the local and global ones. The criteria for formation of non--stationary semi-periodic structures in a system of gravitating particles described by Vlasov--Poisson equations are obtained in the case of that repulsive term. The obtained dispersion relations for the Vlasov equation in the vicinity of the singular point of the modified gravitational potential demonstrate the possibility of the emergence of filaments as coherent complex states of relative equilibrium in non--stationary systems as structures of low dimensions (walls), and voids between them, of scales (diameters) defined by the balance between the gravity and repulsive term of the cosmological constant.

astro-ph.CO↗

arXiv2022

Influence of dark matter on gravitational stability of isothermal gas clouds

To date, the presence of dark matter (DM) can be judged only by its gravitational interaction on the visible matter. It is therefore important to find the consequences of this interaction, which can then help to determine both the DM properties and parameters and the dynamics and evolution of visible matter. The gravitational influence of dark matter on the stability of interstellar medium (ISM), the progenitor of stars and star clusters, was considered. An isothermal self-gravity gas was taken as a suitable model describing ISM, particles interacting only gravitationally were considered as DM. The results obtained by analytical methods show that even a small amount of fast DM particles significantly increases the stable radius of the gas cloud and the corresponding mass while a higher relative density of DM destabilizes the gas. It was shown that with typical parameters of ISM and DM, its presence increases the maximum stable mass of isothermal cloud by a factor of four and the radius by five.

astro-ph.GA↗

arXiv2022

On the origin of cosmic web

The emergence of one and two-dimensional configurations -- Zeldovich pancakes -- progenitors of the observed filaments and clusters and groups of galaxies, is predicted by means of a developed kinetic approach in analyzing the evolution of initial density perturbations. The self-consistent gravitational interaction described by Vlasov-Poisson set of equations with branching conditions is shown to predict two-dimensional structures as of layers of increased density and voids between them, i.e. the cellular macro-structure of the Universe. The modified potential of weak-field General Relativity is involved, which enables one to explain the Hubble tension, revealing the conceptual discrepancy in the local galactic flows and the cosmological expansion. This demonstrates the possible essential role of self-consistent gravity in the formation of the cosmic web.

astro-ph.CO↗

arXiv2020

The modified Newton attraction law and its connection with cosmological $Λ$--term

We consider the possibility of generalizing the Newtonian law of gravity and the transition to a general relativistic model for weak fields with the inclusion of a repulsive term identified as a cosmological constant. The analysis includes that of the test particle's motion in a modified gravitational field of the Hilbert metric and then the problem of the reverse transition from the post-Galilean case to the construction of a modified exact point mass metric which includes the $Λ$-term.

gr-qc↗

arXiv2017

3D modelling of accretion disc in eclipsing binary system V1239 Her

We present the results of 3D-hydrodynamical simulations of accretion flow in the eclipsing dwarf nova V1239 Her in quiescence. The model includes the optical star filling its Roche lobe, a gas stream emanating from the inner Lagrangian point of the binary system, and the accretion disc structure. A cold hydrogen gas stream is initially emitted towards a point-like gravitational centre. A stationary accretion disc is formed in about 15 orbital periods after the beginning of accretion. The model takes into account partial ionization of hydrogen and uses realistic cooling function for hydrogen. The light curve of the system is calculated as the volume emission of optically thin layers along the line of sight up to the optical depth τ=2/3 calculated using Planck-averaged opacities. The calculated eclipse light curves show good agreement with observations, with the changing shape of pre-eclipse and post-eclipse light curves being explained entirely due to ~ 50% variations in the mass accretion rate through the gas stream.

astro-ph.SR↗

arXiv2001

Structure of gaseous flows in semidetached binaries after mass transfer termination

The results of three-dimensional numerical simulations of mass transfer in semidetached binaries after mass transfer termination is presented and the structure of residual accretion disk was investigated. It was shown that after the mass transfer termination the quasi-elliptic accretion disk becomes circular. It was also shown that the cessation of mass transfer results in changing of the structure of the accretion disk: the second arm of spiral shock is appeared as well as a new dense formation (blob), the latter moving through the disk with variable velocity. The blob doesn't smear out under the action of dissipation but is sustained by interaction with arms of spiral shock for practically all the lifetime of the disk. We also analyze the dependence of disk's lifetime on the value of viscosity. For the value of parameter $α$ that is typical for observing accretion disk ($α\sim0.01$) the lifetime of residual disk is found to be equal to 50 orbital periods.

astro-ph↗

arXiv2000

Synthetic Doppler maps of gaseous flows in semidetached binaries based on the results of 3D gas dynamical simulations

We present synthetic Doppler maps of gaseous flows in semidetached binaries based on the results of 3D gas dynamical simulations. Using of gas dynamical calculations alongside with Doppler tomography technique permits to identify main features of the flow on the Doppler maps without solution of ill-posed inverse problem. Comparison of synthetic tomograms with observations makes possible both to refine the gas dynamical model and to interpret the observational data.

astro-ph↗

arXiv2000

Driven-disk model for binaries with precessing donor star. Three-dimensional simulations

We present the results of three-dimensional numerical simulations of mass transfer in semi-detached binary with a donor star whose rotation vector precesses around the orbital rotation axis of the binary in the observer's coordinate frame. The calculations support our previous model of flow without a `hot spot'. Characteristic features of the flow in this model, such as the formation of an circumbinary envelope, the absence of a `hot spot' at the edge of the accretion disk, and the formation of a shock wave along the edge of the stream, are also present in the solution for a binary with precessing donor star. The parameters of accretion disk and of the structure of the near-disk regions recur with the precessional period of the rotation axis of donor star.

astro-ph↗

arXiv1999

Comparison of 2D and 3D models of flow structure in semidetached binaries

We present the results of systematic comparison of 2D and 3D numerical models of mass transfer in semidetached binaries. It is shown that only for case of γ\sim 1 (near-isothermal case) the obtained 2D and 3D solutions are qualitatively similar. For higher value of γthe 3D flow structure is drastically changed and for γ=1.2 the accretion disk is not formed in the system. Numerical results show that for case of γ=1.2 the 2D and 3D solutions are different. We discuss the spiral-shaped shock waves obtained in numerical models. It is shown that these shocks are not intrinsic spirals and are caused by collisions of the gaseous flows in the system.

astro-ph↗

arXiv1999

The impact of viscosity on the morphology of gaseous flows in semidetached binary systems

Results of 3D gas dynamical simulation of mass transfer in binaries are presented for systems with various values of viscosity. Analysis of obtained solutions shows that in the systems with low value of viscosity the flow structure is qualitatively similar to one for systems with high viscosity. Presented calculations confirm that there is no shock interaction between the stream from L1 and the forming accretion disk (`hot spot') at any value of viscosity.

astro-ph↗

arXiv1998

Three-dimensional modeling of mass transfer in close binary systems with non-synchronous rotation

We present the results of three-dimensional numerical simulations of mass transfer in semi-detached binary systems in which the mass-losing star is rotating. The cases of aligned and misaligned non-synchronous rotation of the donor star are considered; the resulting flow patterns are compared to the synchronous case. The main properties of the flow, such as the formation of an circumbinary envelope, the absence of a "hot spot" on the edge of the accretion disk, and the formation of a shock wave along the flow edge, are qualitatively similar to those obtained earlier. For the case of misaligned, non-synchronous rotation, the behavior of the disk and surrounding matter in established flow regime reflects changes in the boundary conditions at the surface of the donor star; in other words, a "driven disk" model is realized in the calculations.

astro-ph↗

arXiv1998

Orbital evolution of a binary neutron star and gravitational radiation

We consider the dependence of the internal structure of a neutron star in a close binary system on the semi-major axis of the binary orbit, focusing on the case when the Roche lobes of the components are nearly filled. We adopt a polytropic equation of state. The temporal evolution of the semi-major axis and its dependence on the mass ratio of the binary components and the polytropic index are determined. The calculation are carried out right up to the moment of contact, when quasi-stationary model becomes invalid. We analyze differences in the shapes of the pulses of gravitational radiation emitted by a pair of point masses and by a binary neutron star, taking into account its internal structure and tidal deformations.

astro-ph↗

arXiv1998

Magneto-centrifugally driven winds: comparison of MHD simulations with theory

Stationary magnetohydrodynamic (MHD) outflows from a rotating, conducting Keplerian accretion disk threaded by B-field are investigated numerically by time-dependent, axisymmetric (2.5D) simulations using a Godunov-type code. A large class of stationary magneto-centrifugally driven winds are found where matter is accelerated from a thermal speed at the disk to much larger velocity, greater than the fast magnetosonic speed and larger than the escape speed. The flows are approximately spherical outflows with only small collimation within the simulation region. Numerical results are shown to coincide with the theoretical predictions of ideal, axisymmetric MHD to high accuracy. Investigation of the influence of outer boundary conditions, particularly that on the toroidal component of magnetic field shows that the commonly used ``free'' boundary condition leads to artificial magnetic forces which can act to give spurious collimation. New boundary conditions are proposed which do not generate artificial forces. Artificial results may also arise for cases where the Mach cones on the outer boundaries are partially directed into the simulation region.

astro-ph↗