10,158 research outputs found
Non trivial generalizations of the Schwinger pair production result II
It is suggested that Schwinger's (1951) vacuum persistence probability
against pair production by an intense but constant electric field is a very
good approximation to the corresponding quantity if the field does not vary
appreciably over distances less than m/e/E/5 pagesComment: 5 page
Flavor Changing Neutral Currents, an Extended Scalar Sector, and the Higgs Production Rate at the LHC
We study extensions of the standard model with additional colored scalar
fields which can couple directly to quarks. Natural suppression of flavor
changing neutral currents implies minimal flavor violation, and fixes the
scalars to transform as (8,2)_1/2 under the SU(3) X SU(2) X U(1) gauge
symmetry. We explore the phenomenology of the standard model with one
additional (8,2)_1/2 scalar, and discuss how this extension can modify flavor
physics and the Higgs boson production rate at the LHC. Custodial SU(2)
symmetry can be implemented for the octet scalars since they transform as a
real color representation. Additional weak scale degrees of freedom needed for
gauge unification are discussed.Comment: Minor change
Linking of the BENSON graph-plotter with the Elektronika-1001 computer
A device, developed by the Institute of Space Research of the Academy of Sciences of the USSR, for linking the Elektronika-100I computer with the BENSON graph-plotter is described. Programs are compiled which provide display of graphic and alphanumeric information. Instructions for their utilization are given
Astrokit -- an Efficient Program for High-Precision Differential CCD Photometry and Search for Variable Stars
Having a need to perform differential photometry for tens of thousands stars
in a several square degrees field, we developed Astrokit program. The software
corrects the star brightness variations caused by variations of atmospheric
transparency: to this end, the program selects for each star an individual
ensemble of reference stars having similar magnitudes and positions in the
frame. With ten or more reference stars in the ensemble, the differences
between their spectral types and the spectral type of the object studied become
unimportant. Astrokit searches for variable stars using Robust Median
Statistics criterion, which allows candidate variables to be selected more
efficiently than by analyzing the standard deviation of star magnitudes. The
software allows very precise automatic analysis of long inhomogeneous sets of
photometric observations of a large number of objects to be performed, making
it possible to find "hot Jupiter" type exoplanet transits and low-amplitude
variables. We describe the algorithm of the program and the results of its
application to reduce the data of the photometric sky survey in Cygnus as well
as observations of the open cluster NGC188 and the transit of the exoplanet
WASP-11 b / HAT-P-10 b, performed with the MASTER-II-URAL telescope of the
Kourovka Astronomical Observatory of the Ural Federal University.Comment: to be published in Astrophysical Bulletin, Vol. 69, No.
Root systems in number fields
We classify the types of root systems in the rings of integers of number fields such that the Weyl group lies in the group generated by and multiplications by the elements of . We also classify the Weyl groups of roots systems of rank which are isomorphic to a subgroup of for a number field of degree over
Giant Pulses with Nanosecond Time Resolution detected from the Crab Pulsar at 8.5 and 15.1 GHz
We present a study of shape, spectra and polarization properties of giant
pulses (GPs) from the Crab pulsar at the very high frequencies of 8.5 and 15.1
GHz. Studies at 15.1 GHz were performed for the first time. Observations were
conducted with the 100-m radio telescope in Effelsberg in Oct-Nov 2007 at the
frequencies of 8.5 and 15.1 GHz as part of an extensive campaign of
multi-station multi-frequency observations of the Crab pulsar. A selection of
the strongest pulses was recorded with a new data acquisition system, based on
a fast digital oscilloscope, providing nanosecond time resolution in two
polarizations in a bandwidth of about 500 MHz. We analyzed the pulse shapes,
polarisation and dynamic spectra of GPs as well as the cross-correlations
between their LHC and RHC signals. No events were detected outside main pulse
and interpulse windows. GP properties were found to be very different for GPs
emitted at longitudes of the main pulse and the interpulse. Cross-correlations
of the LHC and RHC signals show regular patterns in the frequency domain for
the main pulse, but these are missing for the interpulse GPs. We consider
consequences of application of the rotating vector model to explain the
apparent smooth variation in the position angle of linear polarization for main
pulse GPs.
We also introduce a new scenario of GP generation as a direct consequence of
the polar cap discharge. We find further evidence for strong nano-shot
discharges in the magnetosphere of the Crab pulsar. The repetitive frequency
spectrum seen in GPs at the main pulse phase is interpreted as a diffraction
pattern of regular structures in the emission region. The interpulse GPs
however have a spectrum that resembles that of amplitude modulated noise.
Propagation effects may be the cause of the differences.Comment: Astronomy & Astrophysics (accepted
Organization of the channel-switching process in parallel computer systems based on a matrix optical switch
After a classification and analysis of electronic and optoelectronic switching devices, the design principles and structure of a matrix optical switch is described. The switching and pair-exclusion operations in this type of switch are examined, and a method for the optical switching of communication channels is elaborated. Finally, attention is given to the structural organization of a parallel computer system with a matrix optical switch
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