4,725 research outputs found
Stability and hyperfine structure of the four- and five-body muon-atomic clusters and
Based on the results of accurate variational calculations we demonstrate
stability of the five-body negatively charged ions . Each of these five-body ions contains two electrons , one
negatively charged muon and two nuclei of the hydrogen isotopes . The bound state properties of these five-body ions, including
their hyperfine structure, are briefly discussed. We also investigate the
hyperfine structure of the ground states of the four-body muonic quasi-atoms
. In particular, we determine the hyperfine
structure splittings for the ground state of the four-body muonic quasi-atoms:
and
Energy flux through the horizon in the black hole-domain wall systems
We study various configurations in which a domain wall (or cosmic string),
described by the Nambu-Goto action, is embedded in a background space-time of a
black hole in and higher dimensional models. We calculate energy fluxes
through the black hole horizon. In the simplest case, when a static domain wall
enters the horizon of a static black hole perperdicularly, the energy flux is
zero. In more complicated situations, where parameters which describe the
domain wall surface are time and position dependent, the flux is non-vanishing
is principle. These results are of importance in various conventional
cosmological models which accommodate the existence of domain walls and strings
and also in brane world scenarios.Comment: references added, accepted for publication in JHE
Thorny Spheres and Black Holes with Strings
We consider thorny spheres, that is 2-dimensional compact surfaces which are
everywhere locally isometric to a round sphere except for a finite number
of isolated points where they have conical singularities. We use thorny spheres
to generate, from a spherically symmetric solution of the Einstein equations,
new solutions which describe spacetimes pierced by an arbitrary number of
infinitely thin cosmic strings radially directed. Each string produces an angle
deficit proportional to its tension, while the metric outside the strings is a
locally spherically symmetric solution. We prove that there can be arbitrary
configurations of strings provided that the directions of the strings obey a
certain equilibrium condition. In general this equilibrium condition can be
written as a force-balance equation for string forces defined in a flat 3-space
in which the thorny sphere is isometrically embedded, or as a constraint on the
product of holonomies around strings in an alternative 3-space that is flat
except for the strings. In the case of small string tensions, the constraint
equation has the form of a linear relation between unit vectors directed along
the string axes.Comment: 37 pages, 11 figure
Applications of hidden symmetries to black hole physics
This work is a brief review of applications of hidden symmetries to black
hole physics. Symmetry is one of the most important concepts of the science. In
physics and mathematics the symmetry allows one to simplify a problem, and
often to make it solvable. According to the Noether theorem symmetries are
responsible for conservation laws. Besides evident (explicit) spacetime
symmetries, responsible for conservation of energy, momentum, and angular
momentum of a system, there also exist what is called hidden symmetries, which
are connected with higher order in momentum integrals of motion. A remarkable
fact is that black holes in four and higher dimensions always possess a set
(`tower') of explicit and hidden symmetries which make the equations of motion
of particles and light completely integrable. The paper gives a general review
of the recently obtained results. The main focus is on understanding why at all
black holes have something (symmetry) to hide.Comment: This is an extended version of the talks at NEB-14 conference
(June,Ioannina,Greece) and JGRG20 meeting (September, Kyoto, Japan
Statistical Mechanics of Charged Black Holes in Induced Einstein-Maxwell Gravity
The statistical origin of the entropy of charged black holes in models of
induced Einstein-Maxwell gravity is investigated. The constituents inducing the
Einstein-Maxwell action are charged and interact with an external gauge
potential. This new feature, however, does not change divergences of the
statistical-mechanical entropy of the constituents near the horizon. It is
demonstrated that the mechanism of generation of the Bekenstein-Hawking entropy
in induced gravity is universal and it is basically the same for charged and
neutral black holes. The concrete computations are carried out for induced
Einstein-Maxwell gravity with a negative cosmological constant in three
space-time dimensions.Comment: 16 pages, latex, no figure
Weakly magnetized black holes as particle accelerators
We study collision of particles in the vicinity of a horizon of a weakly
magnetized non-rotating black hole. In the presence of the magnetic field
innermost stable circular orbits (ISCO) of charged particles can be located
close to the horizon. We demonstrate that for a collision of two particles, one
of which is charged and revolving at ISCO and the other is neutral and falling
from infinity, the maximal collision energy can be high in the limit of strong
magnetic field. This effect has some similarity with the recently discussed
effect of high center-of-mass energy for collision of particles in extremely
rotating black holes. We also demonstrate that for `realistic' astrophysical
black holes their ability to play the role of `accelerators' is in fact quite
restricted.Comment: 7 pages, 5 figure
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