351 research outputs found
Why does Einasto profile index occur so frequently?
We consider the behavior of spherically symmetric Einasto halos composed of
gravitating particles in the Fokker-Planck approximation. This approach allows
us to consider the undesirable influence of close encounters in the N-body
simulations more adequately than the generally accepted criteria. The Einasto
profile with index is a stationary solution of the Fokker-Planck
equation in the halo center. There are some reasons to believe that the
solution is an attractor. Then the Fokker-Planck diffusion tends to transform a
density profile to the equilibrium one with the Einasto index . We
suggest this effect as a possible reason why the Einasto index
occurs so frequently in the interpretation of N-body simulation results. The
results obtained cast doubt on generally accepted criteria of N-body simulation
convergence.Comment: 7 pages, 2 figures, Accepted to JCA
Accretion of a massive magnetized torus on a rotating black hole
We present numerical simulations of the axisymmetric accretion of a massive
magnetized plasma torus on a rotating black hole. We use a realistic equation
of state, which takes into account neutrino cooling and energy loss due to
nucleus dissociations. We simulated various magnetic field configurations and
torus models, both optically thick and thin for neutrinos. It is shown that the
neutrino cooling does not significantly change either the structure of the
accretion flow or the total energy release of the system. The calculations
evidence heating of the wind surrounding the collapsar by the shock waves
generated at the jet-wind border. This mechanism can give rise to a hot corona
around the binary system like SS433.
Angular momentum of the accreting matter defines the time scale of the
accretion. Due to the absence of the magnetic dynamo in our calculations, the
initial strength and topology of the magnetic field determines magnetization of
the black hole, jet formation properties and the total energy yield. We
estimated the total energy transformed to jets as {ergs}
which was sufficient to explain hypernova explosions like GRB 980425 or GRB
030329.Comment: 11 pages, 9 figures, submitted to MNRA
Rho primes in analyzing e+e- annihilation, MARK III, LASS and ARGUS data
The results of an analysis are presented of some recent data on the reactions
, with the
subtracted events, , , , , the decays
,
, upon taking into account both the strong energy
dependence of the partial widths on energy and the previously neglected mixing
of the type resonances. The above effects are shown to exert an
essential influence on the specific values of masses and coupling constants of
heavy resonances and hence are necessary to be accounted for in establishing
their true nature.Comment: 20 pages, ReVTeX, 9 Postscript figures As compared to hep-ph/9607398,
new material concerning the analysis of the ARGUS data on the tau decays into
four pion hadronic states is adde
Time lag between prompt optical emission and gamma-rays in GRBs
The prompt optical emission contemporaneous with the -rays from
-ray bursts (GRBs) carries important information on the central engine
and explosion mechanism. We study the time lag between prompt optical emission
and -rays in GRB 990123 and GRB 041219a, which are the only two GRBs
had been detected at optical wavelengths during the ascending burst phase.
Assuming profiles of prompt optical light curves are the same as the prompt
-rays, we simulate optical light curves with different time lags and
compare them with the observed optical flux. Then the best fit time lag and its
error are determined by chi-squared values. We find that time lags between
prompt optical emission and -rays in GRB host galaxy rest-frames are
consistent in the two GRBs, which is s for GRB 990123 and s
for GRB 041219a. This result is consistent with a common origin of prompt
optical and -ray emissions in the two GRBs. Based on synchrotron
cooling model, we also derive the parameters for the two GRBs.Comment: 4 pages, 3 figures; accepted for publication in A&
Infrared afterglow of GRB041219 as a result of reradiation on dust in a circumstellar cloud
Observations of gamma ray bursts (GRB) afterglows in different spectral bands
provide a most valuable information about their nature, as well as about
properties of surrounding medium. Powerful infrared afterglow was observed from
the strong GRB041219. Here we explain the observed IR afterglow in the model of
a dust reradiation of the main GRB signal in the envelope surrounding the GRB
source. In this model we do not expect appearance of the prompt optical
emission which should be absorbed in the dust envelope. We estimate the
collimation angle of the gamma ray emission, and obtain restrictions on the
redshift (distance to GRB source), by fitting the model parameters to the
observational data.Comment: 6 pages, 2 figures, Submited to Astrofizik
Electromagnetic form factors in the J/\psi mass region: The case in favor of additional resonances
Using the results of our recent analysis of e^+e^- annihilation, we plot the
curves for the diagonal and transition form factors of light hadrons in the
time-like region up to the production threshold of an open charm quantum
number. The comparison with existing data on the decays of J/\psi into such
hadrons shows that some new resonance structures may be present in the mass
range between 2 GeVand the J/\psi mass. Searching them may help in a better
understanding of the mass spectrum in both the simple and a more sophisticated
quark models, and in revealing the details of the three-gluon mechanism of the
OZI rule breaking in K\bar K channel.Comment: Formulas are added, typo is corrected, the text is rearranged.
Replaced to match the version accepted in Phys Rev
Microwave-induced flow of vortices in long Josephson junctions
We report experimental and numerical study of microwave-induced flow of
vortices in long Josephson junctions at zero dc magnetic field. Our intriguing
observation is that applying an ac-bias of a small frequency and
sufficiently large amplitude changes the current-voltage characteristics
(- curve) of the junction in a way similar to the effect of dc magnetic
field, well known as the flux-flow behavior. The characteristic voltage of
this low voltage branch increases with the power of microwave radiation as
with the index . Experiments
using a low-temperature laser scanning microscope unambiguously indicate the
motion of Josephson vortices driven by microwaves. Numerical simulations agree
with the experimental data and show strongly {\it irregular} vortex motion. We
explain our results by exploiting an analogy between the microwave-induced
vortex flow in long Josephson junctions and incoherent multi-photon absorption
in small Josephson junctions in the presence of large thermal fluctuations. In
the case of long Josephson junctions the spatially-temporal chaos in the vortex
motion mimics the thermal fluctuations. In accordance with this analogy, a
control of the intensity of chaos in a long junction by changing its damping
constant leads to a pronounced change in the shape of the - curve. Our
results provide a possible explanation to previously measured but not yet
understood microwave-driven properties of intrinsic Josephson junctions in
high-temperature superconductors.Comment: 8 pages, 13 figure
A possibility for precise Weinberg angle measurement in centrosymmetric crystals with axis
We demonstrate that parity nonconserving interaction due to the nuclear weak
charge Q_W leads to nonlinear magnetoelectric effect in centrosymmetric
paramagnetic crystals. It is shown that the effect exists only in crystals with
special symmetry axis k. Kinematically, the correlation (correction to energy)
has the form H_PNC ~ Q_W (E,[B,k])(B,k), where B and E are the external
magnetic and electric fields. This gives rise to magnetic induction M_PNC ~ Q_W
{k(B,[k,E]) + [k,E](B,k)}. To be specific we consider rare-earth trifluorides
and, in particular, dysprosium trifluoride which looks the most suitable for
experiment. We estimate the optimal temperature for the experiment to be of a
few kelvin. For the magnetic field B = 1 T and the electric field E = 10 kV/cm,
the expected magnetic induction is 4 \pi M_PNC = 0.5 * 10^-11 G, six orders of
magnitude larger than the best sensitivity currently under discussion.
Dysprosium has several stable isotopes, and so, comparison of the effects for
different isotopes provides possibility for precise measurement of the Weinberg
angle.Comment: 7 pages, 1 figure, 2 tables; version 2 - added discussion of neutron
distribution uncertaint
The Mass Splitting Problem
It is discussed the problem of the mass splitting. It is
suggested to use the decay to measure the
mass splitting.Comment: 7 pages, revtex, a few typos fixed, to be published in Pis'ma v
ZHETF, V. 69, No 1, pp. 8-11, 10 January 199
Gravitational red-shift and deflection of slow light
We explore the nature of the classical propagation of light through media
with strong frequency-dependent dispersion in the presence of a gravitational
field. In the weak field limit, gravity causes a redshift of the optical
frequency, which the slow-light medium converts into a spatially-varying index
of refraction. This results in the bending of a light ray in the medium. We
further propose experimental techniques to amplify and detect the phenomenon
using weak value measurements. Independent heuristic and rigorous derivations
of this effect are given.Comment: 9 pages, 1 figur
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