4,801 research outputs found
Bosonic Quartic Couplings at LEP2
We list the set of C and P conserving anomalous quartic vector bosons
self-couplings which can be tested at LEP2 through triple vector boson
production. We show how this set can be embedded in manifestly SU(2)xU(1) gauge
invariant operators exhibiting an SU(2)_c global symmetry. We derive bounds on
these various couplings and show the most relevant distributions that can
enhance their contribution. We also find that an e+e- collider running at 500
GeV can improve the LEP2 limits by as much as three orders of magnitude.Comment: 21 pages, 7 figure
Design concepts and performance of NASA X-band (7162 MHz/8415 MHz) transponder for deep-space spacecraft applications
The design concepts and measured performance characteristics are summarized of an X band (7162 MHz/8415 MHz) breadboard deep space transponder (DSP) for future spacecraft applications, with the first use scheduled for the Comet Rendezvous Asteroid Flyby (CRAF) and Cassini missions in 1995 and 1996, respectively. The DST consists of a double conversion, superheterodyne, automatic phase tracking receiver, and an X band (8415 MHz) exciter to drive redundant downlink power amplifiers. The receiver acquires and coherently phase tracks the modulated or unmodulated X band (7162 MHz) uplink carrier signal. The exciter phase modulates the X band (8415 MHz) downlink signal with composite telemetry and ranging signals. The receiver measured tracking threshold, automatic gain control, static phase error, and phase jitter characteristics of the breadboard DST are in good agreement with the expected performance. The measured results show a receiver tracking threshold of -158 dBm and a dynamic signal range of 88 dB
GHASP: an H kinematic survey of spiral galaxies - X. Surface photometry, decompositions and the Tully-Fisher relation in the Rc-band
We present Rc-band surface photometry for 170 of the 203 galaxies in GHASP,
Gassendi H-Alpha survey of SPirals, a sample of late-type galaxies for which
high-resolution Fabry-Perot H{\alpha} maps have previously been obtained. Our
data set is constructed by new Rc-band observations taken at the Observatoire
de Haute-Provence (OHP), supplemented with Sloan Digital Sky Survey (SDSS)
archival data, obtained with the purpose of deriving homogeneous photometric
profiles and parameters. Our results include Rc-band surface brightness
profiles for 170 galaxies and profiles for 108 of these objects. We
catalogue several parameters of general interest for further reference, such as
total magnitude, effective radius and isophotal parameters -- magnitude,
position angle, ellipticity and inclination. We also perform a structural
decomposition of the surface brightness profiles using a multi-component method
in order to separate disks from bulges and bars, and to observe the main
scaling relations involving luminosities, sizes and maximum velocities.
We determine the Rc-band Tully Fisher relation using maximum velocities
derived solely from H rotation curves for a sample of 80 galaxies,
resulting in a slope of , zero point of and an
estimated intrinsic scatter of . We note that, different from
the TF-relation in the near-infrared derived for the same sample, no change in
the slope of the relation is seen at the low-mass end (for galaxies with
km/s). We suggest that this different behaviour of the Tully
Fisher relation (with the optical relation being described by a single
power-law while the near-infrared by two) may be caused by differences in the
stellar mass to light ratio for galaxies with km/s.Comment: 17 pages, 11 figure
Radiative damping: a case study
We are interested in the motion of a classical charge coupled to the Maxwell
self-field and subject to a uniform external magnetic field, B. This is a
physically relevant, but difficult dynamical problem, to which contributions
range over more than one hundred years. Specifically, we will study the
Sommerfeld-Page approximation which assumes an extended charge distribution at
small velocities. The memory equation is then linear and many details become
available. We discuss how the friction equation arises in the limit of "small"
B and contrast this result with the standard Taylor expansion resulting in a
second order equation for the velocity of the charge.Comment: 4 figure
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