1,085 research outputs found
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.Comment: 7 pages, 1 figur
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.Comment: 17 pages, 7 figure
Natural noise and external wake field seeding in a proton-driven plasma accelerator
We discuss the level of natural shot noise in a proton bunch-driven plasma
accelerator. The required seeding for the plasma wake field must be larger than
the cumulative shot noise. This is the necessary condition for the axial
symmetry of the generated wake and the acceleration quality. We develop an
analytical theory of the noise field and compare it with multi-dimensional
simulations. It appears that the natural noise wake field generated in plasma
by the available at CERN super-protons-synchrotron (SPS) bunches is very low,
at the level of a few 10 kV/m. This fortunate fact eases the requirements on
the seed. Our three dimensional simulations show that even a few tens MeV
electron bunch precursor of a very moderate intensity is sufficient to seed the
proton bunch self-modulation in plasma.Comment: 5 pages, 5 figure
Mass of perfect fluid black shells
The spherically symmetric singular perfect fluid shells are considered for
the case of their radii being equal to the event horizon (the black shells). We
study their observable masses, depending at least on the three parameters,
viz., the square speed of sound in the shell, instantaneous radial velocity of
the shell at a moment when it reaches the horizon, and integration constant
related to surface mass density. We discuss the features of black shells
depending on an equation of state.Comment: 1 figure, LaTeX; final version + FA
Cosmological String Solutions in 4 Dimensions from 5d Black Holes
We obtain cosmological four dimensional solutions of the low energy effective
string theory by reducing a five dimensional black hole, and black hole--de
Sitter solution of Einstein gravity down to four dimensions. The appearance of
a cosmological constant in the five dimensional Einstein--Hilbert action
produces a special dilaton potential in the four dimensional effective string
action. Cosmological scenarios implemented by our solutions are discussed.Comment: Latex, 3 figures, epsfig.sty, DESY 93-11
On Supergroups with Odd Clifford Parameters and Supersymmetry with Modified Leibniz Rule
We investigate supergroups with Grassmann parameters replaced by odd Clifford
parameters. The connection with non-anticommutative supersymmetry is discussed.
A Berezin-like calculus for odd Clifford variables is introduced. Fermionic
covariant derivatives for supergroups with odd Clifford variables are derived.
Applications to supersymmetric quantum mechanics are made. Deformations of the
original supersymmetric theories are encountered when the fermionic covariant
derivatives do not obey the graded Leibniz property. The simplest non-trivial
example is given by the N=2 SQM with a real multiplet and a cubic
potential. The action is real. Depending on the overall sign ("Euclidean" or
"Lorentzian") of the deformation, a Bender-Boettcher pseudo-hermitian
hamiltonian is encountered when solving the equation of motion of the auxiliary
field. A possible connection of our framework with the Drinfeld twist
deformation of supersymmetry is pointed out.Comment: Final version to be published in Int. J. Mod. Phys. A; 20 page
Covariant perturbations of domain walls in curved spacetime
A manifestly covariant equation is derived to describe the perturbations in a
domain wall on a given background spacetime. This generalizes recent work on
domain walls in Minkowski space and introduces a framework for examining the
stability of relativistic bubbles in curved spacetimes.Comment: 15 pages,ICN-UNAM-93-0
Zel'dovich states with very small mass and charge in nonlinear electrodynamics coupled to gravity
It is shown that in non-linear electrodynamics (in particular, Born-Infeld
one) in the framework of general relativity there exist "weakly singular"
configurations such that (i) the proper mass M is finite in spite of
divergences of the energy density, (ii) the electric charge q and Schwarzschild
mass m ~ q can be made as small as one likes, (iv) all field and energy
distributions are concentrated in the core region. This region has an almost
zero surface area but a finite longitudinal size L=2M. Such configurations can
be viewed as a new version of a classical analogue of an elementary particle.Comment: 11 pages. 1 reference added. To appear in Grav. Cosm
Possible types of the evolution of vacuum shells around the de Sitter space
All possible evolution scenarios of a thin vacuum shell surrounding the
spherically symmetric de Sitter space have been determined and the
corresponding global geometries have been constructed. Such configurations can
appear at the final stage of the cosmological phase transition, when isolated
regions (islands) of the old vacuum remain. The islands of the old vacuum are
absorbed by the new vacuum, expand unlimitedly, or form black holes and
wormholes depending on the sizes of the islands as well as on the density and
velocity of the shells surrounding the islands.Comment: 3 pages, 1 figur
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.Comment: 12 pages, 4 figure
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