arXiv subjects

V. I. Dokuchaev

Publications and source records attributed to V. I. Dokuchaev.

52 records · Page 3Linked to original sources

arXiv2010

Mechanism for the Suppression of Intermediate-Mass Black Holes

A model for the formation of supermassive primordial black holes in galactic nuclei with the simultaneous suppression of the formation of intermediate-mass black holes is presented. A bimodal mass function for black holes formed through phase transitions in a model with a "Mexican hat" potential has been found. The classical motion of the phase of a complex scalar field during inflation has been taken into account. Possible observational manifestations of primordial black holes in galaxies and constraints on their number are discussed.

astro-ph.CO↗

arXiv2010

The wave function of a gravitating shell

We have calculated a discrete spectrum and found an exact analytical solution in the form of Meixner polynomials for the wave function of a thin gravitating shell in the Reissner-Nordstrom geometry. We show that there is no extreme state in the quantum spectrum of the gravitating shell, as in the case of extreme black hole.

gr-qc↗

arXiv2010

Gravitational Wave Bursts from Collisions of Primordial Black Holes in Clusters

The rate of gravitational wave bursts from the mergers of massive primordial black holes in clusters is calculated. Such clusters of black holes can be formed through phase transitions in the early Universe. The central black holes in clusters can serve as the seeds of supermassive black holes in galactic nuclei. The expected burst detection rate by the LISA gravitational wave detector is estimated.

astro-ph.CO↗

arXiv2010

Dynamics of a thin shell in the Reissner-Nordstrom metric

We describe the dynamics of a thin spherically symmetric gravitating shell in the Reissner-Nordstrom metric of the electrically charged black hole. The energy-momentum tensor of electrically neutral shell is modelled by the perfect fluid with a polytropic equation of state. The motion of a shell is described fully analytically in the particular case of the dust equation of state. We construct the Carter-Penrose diagrams for the global geometry of the eternal black hole, which illustrate all possible types of solutions for moving shell. It is shown that for some specific range of initial parameters there are possible the stable oscillating motion of the shell transferring it consecutively in infinite series of internal universes. We demonstrate also that this oscillating type of motion is possible for an arbitrary polytropic equation of state on the shell.

gr-qc↗

arXiv2008

Evolution of a vacuum shell in the Friedman-Schwarzschild world

The method of an effective potential is used to investigate the possible types of evolution of vacuum shells in the Friedman-Schwarzschild world. Such shells are assumed to emerge during phase transitions in the early Universe. The possible global geometries are constructed for the Friedman- Schwarzschild worlds. Approximate solutions to the equation of motion of a vacuum shell have been found. The conditions under which the end result of the evolution of the vacuum shells under consideration is the formation of black holes and wormholes with baby universes inside have been found. The interior of this world can be a closed, flat, or open Friedman universe.

gr-qc↗

arXiv2008

Early formation of galaxies initiated by clusters of primordial black holes

Model of supermassive black holes formation inside the clusters of primordial black holes is developed. Namely, it is supposed, that some mass fraction of the universe ~10^-3 is composed of the compact clusters of primordial (relic) black holes, produced during phase transitions in the early universe. These clusters are the centers of dark matter condensation. We model the formation of protogalaxies with masses about 2*10^8M_sun at the redshift z=15. These induced protogalaxies contain central black holes with mass ~10^5M_sun and look like dwarf spheroidal galaxies with central density spike. The subsequent merging of induced protogalaxies and ordinary dark matter haloes corresponds to the standard hierarchical clustering scenario of large-scale structure formation. The coalescence of primordial black holes results in formation of supermassive black holes in the galactic centers. As a result, the observed correlation between the masses of central black holes and velocity dispersion in the galactic bulges is reproduced.

astro-ph↗

arXiv2007

Origin of supermassive black holes

The origin of supermassive black holes in the galactic nuclei is quite uncertain in spite of extensive set of observational data. We review the known scenarios of galactic and cosmological formation of supermassive black holes. The common drawback of galactic scenarios is a lack of time and shortage of matter supply for building the supermassive black holes in all galaxies by means of accretion and merging. The cosmological scenarios are only fragmentarily developed but propose and pretend to an universal formation mechanism for supermassive black holes.

astro-ph↗

arXiv2007

Vacuum shell in the Schwarzschild-de Sitter world

We construct the classification scheme for all possible evolution scenarios and find the corresponding global geometries for dynamics of a thin spherical vacuum shell in the Schwarzschild-de Sitter metric. This configuration is suitable for the modelling of vacuum bubbles arising during cosmological phase transitions in the early Universe. The distinctive final types of evolution from the local point of view of a rather distant observer are either the unlimited expansion of the shell or its contraction with a formation of black hole (with a central singularity) or wormhole (with a baby universe in interior).

gr-qc↗

arXiv2002

Self-similar spherical shock solution with sustained energy injection

We present the generalization of the Sedov-Taylor self-similar strong spherical shock solution for the case of a central energy source varying in time, $E=A t^k$, where $A$ and $k$ are constants. The known Sedov-Taylor solution corresponds to a particular adiabatic case of $k=0$ or \emph{instant shock} with an instant energy source of the shock, $E=A$. The self-similar hydrodynamic flow in the nonadiabatic $k\neq0$ case exists only under the appropriate local entropy (energy) input which must be supported by some radiative mechanism from the central engine. The specific case of $k=1$ corresponds to a permanent energy injection into the shock, or injection shock with a central source of constant luminosity, $L=A$, $E=A t$. The generalized self-similar shock solution may be applied to astrophysical objects in which the duration of central source activity is longer than the shock expansion time, e.g. the early phase of SN explosions, strong wind from stars and young pulsars, non-steady spherical outflow from black holes and collapsing dense stellar clusters with numerous neutron star collisions.

astro-ph↗

arXiv2002

Origin of Correlations between Central Black Holes Masses and Galactic Bulge Velocity Dispersions

We argue that the observed correlations between central black holes masses M_{BH} and galactic bulge velocity dispersions σ_e in the form M_{BH}\proptoσ_e^4 may witness on the pregalactic origin of massive black holes. Primordial black holes would be the centers for growing protogalaxies which experienced multiple mergers with ordinary galaxies. This process is accompanied by the merging of black holes in the galactic nuclei.

astro-ph↗

arXiv2002

Stochastic Correlation Model of Galactic Bulge Velocity Dispersions and Central Black Holes Masses

We consider the cosmological model in which a part of the Universe Ω_h\sim 10^-5 is in the form of primordial black holes with mass \sim 10^5M_\odot. These primordial black holes would be centers for growing protogalaxies which experienced multiple mergers with ordinary galaxies. This process of galaxies formation is accompanied by the merging of central black holes in the galactic nuclei. It is shown that recently discovered correlations between the central black holes and bulges of galaxies are naturally reproduced in this scenario.

astro-ph↗

arXiv2002

A Common Origin of Neutralino Stars and Supermassive Black Holes

To account for the microlensing events observed in the Galactic halo, Gurevich, Zybin, and Sirota have proposed a model of gravitationally bound, noncompact objects with masses of 0.01-1M_\odot. These objects are formed in the expanding Universe from adiabatic density perturbations and consist of weakly interacting particles of dark matter, for example, neutralinos. They assumed the perturbation spectrum on some small scale to have a distinct peak. We show that the existence of this peak would inevitably give rise to a large number of primordial black holes (PBHs) with masses of \sim10^5M_\odot at the radiation-dominated evolutionary stage of the Universe. Constraints on the coefficient of nonlinear contraction and on the compactness parameter of noncompact objects were derived from constraints on the PBH number density. We show that noncompact objects can serve as gravitational lenses only at a large PBH formation threshold, δ_c > 0.5, or if noncompact objects are formed from entropic density perturbations.

astro-ph↗

arXiv2000

Hidden source of high-energy neutrinos in collapsing galactic nucleus

We propose the model of a short-lived very powerful source of high energy neutrinos. It is formed as a result of the dynamical evolution of a galactic nucleus prior to its collapse into a massive black hole and formation of high-luminosity AGN. This stage can be referred to as ``pre-AGN''. A dense central stellar cluster in the galactic nucleus on the late stage of evolution consists of compact stars (neutron stars and stellar mass black holes). This cluster is sunk deep into massive gas envelope produced by destructive collisions of a primary stellar population. Frequent collisions of neutron stars in a central stellar cluster are accompanied by the generation of ultrarelativistic fireballs and shock waves. These repeating fireballs result in a formation of the expanding rarefied cavity inside the envelope. The charged particles are effectively accelerated in the cavity and, due to pp-collisions in the gas envelope, they produce high energy neutrinos. All high energy particles, except neutrinos, are absorbed in the thick envelope. Duration of this pre-AGN phase is about 10 yr, the number of the sources can be \~ 10 per cosmological horizon. High energy neutrino signal can be detected by underground neutrino telescope with effective area ~1 km^2.

astro-ph↗

arXiv1999

The Eddington Luminosity Phase in Quasars: Duration and Implications

Non-steady and eruptive phenomena in quasars are thought to be associated with the Eddington or super-Eddington luminous stage. Although there is no lack in hypotheses about the total duration of such a stage, the latter remains essentially unknown. We calculate the duration of quasar luminous phase in dependence upon the initial mass of a newborn massive black hole (MBH) by comparing the observed luminosity- and redshift distributions of quasars with mass distribution of the central MBHs in normal galactic nuclei. It is assumed that, at the quasar stage, each MBH goes through a single (or recurrent) phase(s) of accretion with, or close to, the Eddington luminosity. The mass distributions of quasars is found to be connected with that of MBHs residing in normal galaxies by a one-to-one corrrespondence through the entire mass range of the inferred MBHs if the accretion efficiency of mass-to-energy transformation $η\sim 0.1$.

astro-ph↗

arXiv1998

GRB Redshift Distribution is Consistent with GRB Origin in Evolved Galactic Nuclei

Recently we have elaborated a new cosmological model of gamma-ray burst (GRB) origin (1998, ApJ 502, 192), which employs the dynamical evolution of central dense stellar clusters in the galactic nuclei. Those clusters inevitably contain a large fraction of compact stellar remnants (CSRs), such as neutron stars (NSs) and stellar mass black holes (BHs), and close encounters between them result in radiative captures into short-living binaries, with subsequent merging of the components, thereby producing GRBs (typically at large distances from the nucleus). In the present paper, we calculate the redshift distribution of the rate of GRBs produced by close encounters of NSs in distant galactic nuclei. To this end, the following steps are undertaken: (i) we establish a connection between the parameters of the fast evolving central stellar clusters (i.e. those for which the time of dynamical evolution exceeds the age of the Universe) with masses of the forming central supermassive black holes (SMBHs) using a dynamical evolution model; (ii) we connect these masses with the inferred mass distributions of SMBHs in the galactic nuclei and the redshift distribution of quasars by assuming a certain `Eddington luminosity phase' in their activity; (iii) we incorporate available observational data on the redshift distribution of quasars as well as a recently found correlation between the masses of galaxies and their central SMBHs. The resulting redshift distribution of the GRB rate, which accounts for both fast and slowly evolving galactic nuclei is consistent with that inferred from the BATSE data if the fraction of fast evolving galactic nuclei is in the range $0.016-0.16$.

astro-ph↗

arXiv1998

Gamma Ray Bursts from the Evolved Galactic Nuclei

A new cosmological scenario for the origin of gamma ray bursts (GRBs) is proposed. In our scenario, a highly evolved central core in the dense galactic nucleus is formed containing a subsystem of compact stellar remnants (CSRs), such as neutron stars and black holes. Those subsystems result from the dynamical evolution of dense central stellar clusters in the galactic nuclei through merging of stars, thereby forming (as has been realized by many authors) the short-living massive stars and then CSRs. We estimate the rate of random CSR collisions in the evolved galactic nuclei by taking into account, similar to Quinlan & Shapiro (1987), the dissipative encounters of CSRs, mainly due to radiative losses of gravitational waves, which results in the formation of intermediate short-living binaries, with further coalescence of the companions to produce GRBs. We also consider how the possible presence of a central supermassive black hole, formed in a highly evolved galactic nucleus, influences the CSR binary formation. This scenario does not postulate ad hoc a required number of tight binary neutron stars in the galaxies. Instead, it gives, for the most realistic parameters of the evolved nuclei, the expected rate of GRBs consistent with the observed one, thereby explaining the GRB appearance in a natural way of the dynamical evolution of galactic nuclei. In addition, this scenario provides an opportunity for a cosmological GRB recurrence, previously considered to be a distinctive feature of GRBs of a local origin only. We also discuss some other observational tests of the proposed scenario.

astro-ph↗