2,822 research outputs found
Life inside black holes
We consider test planet and photon orbits of the third kind inside a black
hole, which are stable, periodic and neither come out of the black hole nor
terminate at the singularity. Interiors of supermassive black holes may be
inhabited by advanced civilizations living on planets with the third-kind
orbits. In principle, one can get information from the interiors of black holes
by observing their white hole counterparts.Comment: 4 pages, 2 figure
Coleman - de Luccia instanton of the second order in a brane world
The second order Coleman - de Luccia instanton and its action in the Randall
- Sundrum type II model are investigated and the comparison with the results in
Einstein's general relativity is done in the present paper.Comment: 4 pages, accepted in IJT
False vacuum decay in a brane world cosmological model
The false vacuum decay in a brane world model is studied in this work. We
investigate the vacuum decay via the Coleman-de Luccia instanton, derive
explicit approximative expressions for the Coleman-de Luccia instanton which is
close to a Hawking-Moss instanton and compare the results with those already
obtained within Einstein's theory of relativity.Comment: minor changes done, references added, version to appear in GR
Equilibrium conditions of spinning test particles in Kerr-de Sitter spacetimes
Equilibrium conditions and spin dynamics of spinning test particles are
discussed in the stationary and axially symmetric Kerr-de Sitter black-hole or
naked-singularity spacetimes. The general equilibrium conditions are
established, but due to their great complexity, the detailed discussion of the
equilibrium conditions and spin dynamics is presented only in the simple and
most relevant cases of equilibrium positions in the equatorial plane and on the
symmetry axis of the spacetimes. It is shown that due to the combined effect of
the rotation of the source and the cosmic repulsion the equilibrium is spin
dependent in contrast to the spherically symmetric spacetimes. In the
equatorial plane, it is possible at the so-called static radius, where the
gravitational attraction is balanced by the cosmic repulsion, for the spinless
particles as well as for spinning particles with arbitrarily large
azimuthal-oriented spin or at any radius outside the ergosphere with a
specifically given spin orthogonal to the equatorial plane. On the symmetry
axis, the equilibrium is possible at any radius in the stationary region and is
given by an appropriately tuned spin directed along the axis. At the static
radii on the axis the spin of particles in equilibrium must vanish
Anomalous Soft Photons in Hadron Production
Anomalous soft photons in excess of what is expected from electromagnetic
bremsstrahlung have been observed in association with the production of
hadrons, mostly mesons, in high-energy (K+)p, (pi+)p, (pi-)p, pp, and (e+)(e-)
collisions. We propose a model for the simultaneous production of anomalous
soft photons and mesons in quantum field theory, in which the meson production
arises from the oscillation of color charge densities of the quarks of the
underlying vacuum in the flux tube. As a quark carries both a color charge and
an electric charge, the oscillation of the color charge densities will be
accompanied by the oscillation of electric charge densities, which will in turn
lead to the simultaneous production of soft photons during the meson production
process. How the production of these soft photons may explain the anomalous
soft photon data will be discussed. Further experimental measurements to test
the model will be proposed.Comment: 19 pages, 2 figures, to be published in Physical Review
Role of electric charge in shaping equilibrium configurations of fluid tori encircling black holes
Astrophysical fluids may acquire non-zero electrical charge because of strong
irradiation or charge separation in a magnetic field. In this case,
electromagnetic and gravitational forces may act together and produce new
equilibrium configurations, which are different from the uncharged ones.
Following our previous studies of charged test particles and uncharged perfect
fluid tori encircling compact objects, we introduce here a simple test model of
a charged perfect fluid torus in strong gravitational and electromagnetic
fields. In contrast to ideal magnetohydrodynamic models, we consider here the
opposite limit of negligible conductivity, where the charges are tied
completely to the moving matter. This is an extreme limiting case which can
provide a useful reference against which to compare subsequent more complicated
astrophysically-motivated calculations. To clearly demonstrate the features of
our model, we construct three-dimensional axisymmetric charged toroidal
configurations around Reissner-Nordstr\"om black holes and compare them with
equivalent configurations of electrically neutral tori.Comment: 14 pages, 7 figure
False vacuum decay with gravity in a critical case
The vacuum decay in a de Sitter universe is studied within semiclassical
approximation for the class of effective inflaton potentials whose curvature at
the top is close to a critical value. By comparing the actions of the Hawking -
Moss instanton and the Coleman - de Luccia instanton(s) the mode of vacuum
decay is determined. The case when the fourth derivative of the effective
potential at its top is less than a critical value is discussed.Comment: 10 pages, 8 figures, minor changes don
Is there life inside black holes?
Bound inside rotating or charged black holes, there are stable periodic
planetary orbits, which neither come out nor terminate at the central
singularity. Stable periodic orbits inside black holes exist even for photons.
These bound orbits may be defined as orbits of the third kind, following the
Chandrasekhar classification of particle orbits in the black hole gravitational
field. The existence domain for the third kind orbits is rather spacious, and
thus there is place for life inside supermassive black holes in the galactic
nuclei. Interiors of the supermassive black holes may be inhabited by
civilizations, being invisible from the outside. In principle, one can get
information from the interiors of black holes by observing their white hole
counterparts.Comment: 11 pages, 5 figures; references adde
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