5,496 research outputs found
Muons with E_th >= 1 Gev and Mass Composition in the Energy Range 10^{18}-10^{20} ev Observed by Yakutsk Eas Array
The ratio of the muon flux density to charged particle flux density at
distances of 300 and 600 m from the shower axis (\rhom(300)/\rhos(300) and
\rhom(600)/\rhos(600)) is measured. In addition, the energy dependence of
\rhom(1000) is analysed for showers with energies above eV. A
comparison between the experimental data and calculations performed with the
QGSJET model is given for the cases of primary proton, iron nucleus and gamma-
ray. We conclude that the showers with \E\ge3\times10^{18} eV can be formed
by light nuclei with a pronounced fraction of protons and helium nuclei. It is
not excluded however that a small part of showers with energies above
eV could be initiated by primary gamma-rays.Comment: 19th European Cosmic Ray Symposium, Aug 30 - Sep 3 2004, Florence,
Italy. 3 pages, 1 figure. Submitted for publication in International Journal
of Modern Physics
Reverberation measurement of the inner radius of the dust torus in NGC 4151 during 2008-2013
We investigate the correlation between infrared (JHKL) and optical (B) fluxes
of the variable nucleus of the Seyfert galaxy NGC 4151 using partially
published data for the last 6 years (2008-2013.). Here we are using the same
data as in Oknyansky et al. (2014), but include also optical (B) data from Guo
et al. We find that the lag of flux in all the infrared bands is the same, 40
+- 6 days, to within the measurement accuracy. Variability in the J and K bands
is not quite simultaneous, perhaps due to the differing contributions of the
accretion disk in these bands. The lag found for the K band compared with the B
band is not significantly different from earlier values obtained for the period
2000-2007. However, finding approximately the same lags in all IR bands for
2008-2013 differs from previous results at earlier epochs when the lag
increased with increasing wavelength. Examples of almost the same lag in
different IR bands are known for some other active nuclei. In the case of NGC
4151 it appears that the relative lags between the IR bands may be different in
different years. The available data, unfortunately, do not allow us to
investigate a possible change in the lags during the test interval. We discuss
our results in the framework of the standard model where the variable infrared
radiation is mainly due to thermal re-emission from the part of the dusty torus
closest to the central source. There is also a contribution of some IR emission
from the accretion disk, and this contribution increases with decreasing
wavelength. Some cosmological applications of obtained results are discussed.Comment: 3 pages, 2 figures, 14-th Odessa International Astronomical Gamow
Conference-School Astronomy and beyond: Astrophysics, Cosmology and
Gravitation, Cosmomicrophysics, Radio-astronomy and Astrobiolog
Theory of high-T_c superconductivity based on the fermion-condensation quantum phase transition
A theory of high temperature superconductivity based on the combination of
the fermion-condensation quantum phase transition and the conventional theory
of superconductivity is presented. This theory describes maximum values of the
superconducting gap which can be as big as , with
being the Fermi level. We show that the critical temperature
. If there exists the pseudogap above then
, and is the temperature at which the pseudogap
vanishes. A discontinuity in the specific heat at is calculated. The
transition from conventional superconductors to high- ones as a function
of the doping level is investigated. The single-particle excitations and their
lineshape are also considered.Comment: 6 pages, Revte
Color Effects Associated with the 1999 Microlensing Brightness Peaks in Gravitationally Lensed Quasar Q2237+0305
Photometry of the Q2237+0305gravitational lens in VRI spectral bands with the
1.5-m telescope of the high-altitude Maidanak observatory in 1995-2000 is
presented. Monitoring of Q2237+0305 in July-October 2000, made at nearly daily
basis, did not reveal rapid (night-to-night and intranight) variations of
brightness of the components during this time period. Rather slow changes of
magnitudes of the components were observed, such as 0.08 mag fading of B and C
components and 0.05 mag brightening of D in R band during July 23 - October 7,
2000. By good luck three nights in 1999 were almost at the time of the strong
brightness peak of image C, and approximately in the middle of the ascending
slope of the image A brightness peak. The C component was the most blue one in
the system in 1998 and 1999, having changed its (V-I) color from 0.56 mag to
0.12 mag since August 1997, while its brightness increased almost 1.2 mag
during this time period. The A component behaved similarly between August 1998
and August 2000, having become 0.47 mag brighter in R, and at the same time,
0.15 mag bluer. A correlation between the color variations and variations of
magnitudes of the components is demonstrated to be significant and reaches
0.75, with a regression line slope of 0.33. A color (V-I) vrs color (V-R) plot
shows the components settled in a cluster, stretched along a line with a slope
of 1.31. Both slopes are noticeably smaller than those expected if a standard
galactic interstellar reddening law were responsible for the differences
between the colors of images and their variations over time. We attribute the
brightness and color changes to microlensing of the quasar's structure, which
we conclude is more compact at shorter wavelengths, as predicted by most quasar
models featuring an energizing central source.Comment: 14 pages, 7 figures, LaTeX, submitted to A&
Image reconstruction technique and optical monitoring of the QSO2237+0305 from Maidanak Observatory in 2002 -- 2003
We have observed the gravitational lens system Q2237+0305 from the Maidanak
Observatory over the period from August 2002 to November 2003. Here we report
the results of our observations. We implemented a two-stage technique that has
been developed specifically for the purpose of gravitational lens image
reconstruction. The technique is based on the Tikhonov regularization approach
and allows one to obtain astrometric and photometric characteristics of the
gravitational lens system. Light curves with 78 data points for the four quasar
components are obtained. Slow brightness variations over the observational
period are found in all components. Images A, C, D have a tendency to decrease
in brightness. Image B does not vary more than 0.05mag. The observations did
not reveal evidence for large variations in brightness of the components due to
microlensing effects. To provide an overall picture of the photometry
behaviour, our data are combined with the Maidanak observations published for
1995 -- 2000.Comment: 9 pages, 4 figures, accepted by MNRA
Two Scenarios of the Quantum Critical Point
Two different scenarios of the quantum critical point (QCP), a
zero-temperature instability of the Landau state, related to the divergence of
the effective mass, are investigated. Flaws of the standard scenario of the
QCP, where this divergence is attributed to the occurrence of some second-order
phase transition, are demonstrated. Salient features of a different {\it
topological} scenario of the QCP, associated with the emergence of bifurcation
points in equation that ordinarily determines the Fermi
momentum, are analyzed. The topological scenario of the QCP is applied to
three-dimensional (3D) Fermi liquids with an attractive current-current
interaction.Comment: 6 pages, added new discussion and 2 figure
Electron neutrino tagging through tertiary lepton detection
We discuss an experimental technique aimed at tagging electron neutrinos in
multi-GeV artificial sources on an event-by-event basis. It exploits in a novel
manner calorimetric and tracking technologies developed in the framework of the
LHC experiments and of rare kaon decay searches. The setup is suited for
slow-extraction, moderate power beams and it is based on an instrumented decay
tunnel equipped with tagging units that intercept secondary and tertiary
leptons from the bulk of undecayed \pi^+ and protons. We show that the taggers
are able to reduce the \nue contamination originating from K_e3 decays by about
one order of magnitude. Only a limited suppression (~60%) is achieved for \nue
produced by the decay-in-flight of muons; for low beam powers, similar
performance as for K_e3 can be reached supplementing the tagging system with an
instrumented beam dump.Comment: 19 pages, 7 figures; minor changes, version to appear in EPJ
Інженерія програмного забезпечення
Містить теоретичні та практичні відомості про інженерію програмного забезпечення, які включають процес розроблення програмного забезпечення, типові підходи до архітектурного проектування, принципи побудови об’єктно-орієнтованих програмних систем, основи візуального проектування і тестування програмних систем. Розглянуто підходи до оцінювання якості об’єктно-програмних систем на основі відомих метричних показників.Містить теоретичні та практичні відомості про інженерію програмного забезпечення, які включають процес розроблення програмного забезпечення, типові підходи до архітектурного проектування, принципи побудови об’єктно-орієнтованих програмних систем, основи візуального проектування і тестування програмних систем. Розглянуто підходи до оцінювання якості об’єктно-програмних систем на основі відомих метричних показників
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