9,524 research outputs found
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
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
Pair creation in transport equations using the equal-time Wigner function
Based on the equal-time Wigner function for the Klein-Gordon field, we
discuss analytically the mechanism of pair creation in a classical
electromagnetic field including back-reaction. It is shown that the equations
of motion for the Wigner function can be reduced to a variable-frequency
oscillator. The pair-creation rate results then from a calculation analogous to
barrier penetration in nonrelativistic quantum mechanics. The Wigner function
allows one to utilize this treatment for the formulation of an effective
transport theory for the back-reaction problem with a pair-creation source term
including Bose enhancement.Comment: 19 pages, LaTeX, UFTP 316/199
Effect of transient pinning on stability of drops sitting on an inclined plane
We report on new instabilities of the quasi-static equilibrium of water drops
pinned by a hydrophobic inclined substrate. The contact line of a statically
pinned drop exhibits three transitions of partial depinning: depinning of the
advancing and receding parts of the contact line and depinning of the entire
contact line leading to the drop's translational motion. We find a region of
parameters where the classical Macdougall-Ockrent-Frenkel approach fails to
estimate the critical volume of the statically pinned inclined drop
Schwinger Pair Production in dS_2 and AdS_2
We study Schwinger pair production in scalar QED from a uniform electric
field in dS_2 with scalar curvature R_{dS} = 2 H^2 and in AdS_2 with R_{AdS} =
- 2 K^2. With suitable boundary conditions, we find that the pair-production
rate is the same analytic function of the scalar curvature in both cases.Comment: RevTex 6 pages, no figure; replaced by the version published in PR
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