2,866 research outputs found
Quantum amplification effect in a horizon fluctuations
The appearance of a few unevenly- spaced bright flashes of light on top of
Hawking radiation is the sign of the amplification effect in black hole horizon
fluctuations. Previous studies on this problem suffer from the lack of
considering all emitted photons in the theoretical spectroscopy of these
fluctuations. In this paper, we include all of the physical transition weights
and present a consistent intensity formula. This modifies a black hole
radiation pattern.Comment: 6 pages, 2 figure
On chaotic behavior of gravitating stellar shells
Motion of two gravitating spherical stellar shells around a massive central
body is considered. Each shell consists of point particles with the same
specific angular momenta and energies. In the case when one can neglect the
influence of gravitation of one ("light") shell onto another ("heavy") shell
("restricted problem") the structure of the phase space is described. The
scaling laws for the measure of the domain of chaotic motion and for the
minimal energy of the light shell sufficient for its escape to infinity are
obtained.Comment: e.g.: 12 pages, 8 figures, CHAOS 2005 Marc
Magnetic field of Josephson vortices outside superconductors
We consider the structure of Josephson vortices approaching the junction
boundary with vacuum in large area Josephson junctions with the Josephson
length large relative to the London penetration depth .
Using the stability argument for one-dimentional solitons with respect to 2D
perturbations, it is shown that on the scale the Josephson vortices
do not spread near the boundary in the direction of the junction. %, which is
in a striking difference with behavior of Abrikosov vortices exiting
superconductors. The field distribution in vacuum due to the Josephson vortex
is evaluated, the information needed for the Scanning SQUID Microscopy.Comment: 5 RevTeX pages, 3 eps figures. The second version includes more
detailed explanations and corrections, and slightly modified figure
Thermal Duality and Hagedorn Transition from p-adic Strings
We develop the finite temperature theory of p-adic string models. We find
that the thermal properties of these non-local field theories can be
interpreted either as contributions of standard thermal modes with energies
proportional to the temperature, or inverse thermal modes with energies
proportional to the inverse of the temperature, leading to a "thermal duality"
at leading order (genus one) analogous to the well known T-duality of string
theory. The p-adic strings also recover the asymptotic limits (high and low
temperature) for arbitrary genus that purely stringy calculations have yielded.
We also discuss our findings surrounding the nature of the Hagedorn transition.Comment: 4 pages and 4 figure
On Quantum Nature of Black-Hole Spacetime: A Possible New Source of Intense Radiation
Atoms and the planets acquire their stability from the quantum mechanical
incompatibility of the position and momentum measurements. This incompatibility
is expressed by the fundamental commutator [x, p_x]=i hbar, or equivalently,
via the Heisenberg's uncertainty principle Delta x Delta p_x sim hbar. A
further stability-related phenomenon where the quantum realm plays a dramatic
role is the collapse of certain stars into white dwarfs and neutron stars.
Here, an intervention of the Pauli exclusion principle, via the fermionic
degenerate pressure, stops the gravitational collapse. However, by the
neutron-star stage the standard quantum realm runs dry. One is left with the
problematic collapse of a black hole. This essay is devoted to a concrete
argument on why the black-hole spacetime itself should exhibit a quantum
nature. The proposed quantum aspect of spacetime is shown to prevent the
general-relativistic dictated problematic collapse. The quantum nature of
black-hole spacetime is deciphered from a recent result on the universal
equal-area spacing [=lambda_P^2 4 ln(3)] for black holes. In one interpretation
of the emergent picture, an astrophysical black hole can fluctuate to
sqrt{pi/ln(3)} approx 1.7 times its classical size, and thus allow radiation
and matter to escape to the outside observers. These fluctuations I conjecture
provide a new source, perhaps beyond Hawking radiation, of intense radiation
from astrophysical black holes and may be the primary source of observed
radiation from those galactic cores what carry black hole(s). The presented
interpretation may be used as a criterion to choose black holes from black hole
candidates.Comment: This essay received an "honorable mention" in the 1999 Essay
Competition of the Gravity Research Foundation - Ed. Int. J. Mod. Phys. D
(1999, in press). For Joseph Knech
Statistics of fluctuations for two types of crossover: from ballistic to diffusive regime and from orthogonal to unitary ensemble
In our previous publication [Kogan et al, Phys. Rev. {\bf 48}, 9404 (1993)]
we considered the issue of statistics of radiation diffusively propagating in a
disordered medium. The consideration was in the framework of diagrammatic
techniques and a new representation for the intensity distribution function in
terms of connected diagrams only was proposed. Here we use similar approach to
treat the issue of statistics in the regime of the crossover between ballistic
and diffusive transport. We find that even small contribution from coherent
component decreases by one half the intensity distribution function for small
values of intensity and also produces oscillations of the distribution
function. We also apply this method to study statistics of fluctuations of wave
functions of chaotic electrons in a quantum dot in an arbitrary magnetic field,
by calculating the single state local density in the regime of the crossover
between the orthogonal and unitary ensemble.Comment: Revtex, 3 pages + 2 ps.figures in uuencoded file, a version which
clarifies and unites the results of two previous submission
A Cosmic Battery Reconsidered
We revisit the problem of magnetic field generation in accretion flows onto
black holes owing to the excess radiation force on electrons. This excess force
may arise from the Poynting-Robertson effect.
Instead of a recent claim of the generation of dynamically important magnetic
fields, we establish the validity of earlier results from 1977 which show only
small magnetic fields are generated.
The radiative force causes the magnetic field to initially grow linearly with
time. However, this linear growth holds for only a {\it restricted} time
interval which is of the order of the accretion time of the matter.
The large magnetic fields recently found result from the fact that the linear
growth is unrestricted.
A model of the Poynting-Robertson magnetic field generation close to the
horizon of a Schwarzschild black hole is solved exactly using General
Relativity, and the field is also found to be dynamically insignificant.
These weak magnetic fields may however be important as seed fields for
dynamos.Comment: Astrophysical Journal (accepted
Effect of graded physical load on the state of the liver from morphometric data and biochemical blood indices of rats against a background of hypokinesia
Tests were conducted on 100 sexually immature inbred August and Wistar male rats in order to determine the effects hypokinesia, physical load and phenamine on the liver. Weight and linear dimension fell in hypokinesia; total serum protein lowered and aldolase and cholesterol and beta-lipoprotein levels rose. Blood sugar content rose and liver glycogen fell. Interlinear differences of these indices are found. Rehabilitated physical loading against hypokinesia background diminished and at times completely prevented its negative effect. Extent of correction depended on animal species. Evidence of genotypical conditionality of organism adaptation to physical load in hypokinesia was found
Conductance noise in interacting Anderson insulators driven far from equilibrium
The combination of strong disorder and many-body interactions in Anderson
insulators lead to a variety of intriguing non-equilibrium transport phenomena.
These include slow relaxation and a variety of memory effects characteristic of
glasses. Here we show that when such systems are driven with sufficiently high
current, and in liquid helium bath, a peculiar type of conductance noise can be
observed. This noise appears in the conductance versus time traces as
downward-going spikes. The characteristic features of the spikes (such as
typical width) and the threshold current at which they appear are controlled by
the sample parameters. We show that this phenomenon is peculiar to hopping
transport and does not exist in the diffusive regime. Observation of
conductance spikes hinges also on the sample being in direct contact with the
normal phase of liquid helium; when this is not the case, the noise exhibits
the usual 1/f characteristics independent of the current drive. A model based
on the percolative nature of hopping conductance explains why the onset of the
effect is controlled by current density. It also predicts the dependence on
disorder as confirmed by our experiments. To account for the role of the bath,
the hopping transport model is augmented by a heuristic assumption involving
nucleation of cavities in the liquid helium in which the sample is immersed.
The suggested scenario is analogous to the way high-energy particles are
detected in a Glaser's bubble chamber.Comment: 15 pages 22 figure
- …