3,988 research outputs found
The role of energy-momentum conservation in emission of Cherenkov gluons
The famous formula for the emission angle of Cherenkov radiation should be
modified when applied to hadronic reactions because of recoil effects. They
impose the upper limit on the energy of the gluon emitted at a given angle.
Also, it leads to essential corrections to the nuclear refractive index value
as determined from the angular position of Cherenkov rings.Comment: 6
On a Coherent Radioemission Mechanism in Quasars and in the Remains of Supernovae
Coherent radio emission mechanism in quasars and remains of supernova
Current in narrow channels of anisotropic superconductors
We argue that in channels cut out of anisotropic single crystal
superconductors and narrow on the scale of London penetration depth, the
persistent current must cause the transverse phase difference provided the
current does not point in any of the principal crystal directions. The
difference is proportional to the current value and depends on the anisotropy
parameter, on the current direction relative to the crystal, and on the
transverse channel dimension. An experimental set up to measure the transverse
phase is proposed.Comment: 3 pages, 1 figur
Single Leptoquark Production at and Colliders
We consider single production of leptoquarks (LQ's) at and
colliders, for two values of the centre-of-mass energy,
GeV and 1 TeV. We find that LQ's which couple within the first
generation are observable for LQ masses almost up to the kinematic limit, both
at and colliders, for the LQ coupling strength equal to
. The cross sections for single production of - and
-generation LQ's at colliders are too small to be observable.
In collisions, on the other hand, -generation LQ's with
masses much larger than can be detected. However,
-generation LQ's can be seen at colliders only for
masses at most , making their observation more probable via the
pair production mechanism.Comment: plain TeX, 14 pages, 6 figures (not included but available on
request), some minor changes to the text, one reference added, figures and
conclusions unchanged, UdeM-LPN-TH-93-152, McGill-93/2
Effective Potential for Scalar Field in Three Dimensions: Ising Model in the Ferromagnetic Phase
We compute the effective potential for one-component real
scalar field in three Euclidean dimensions (3D) in the case of
spontaneously broken symmetry, from the Monte Carlo simulation of the 3D Ising
model in external field at temperatures approaching the phase transition from
below. We study probability distributions of the order parameter on the
lattices from to , at . We find that, in close
analogy with the symmetric case, plays an important role: is very well approximated by the sum of , and
terms. An unexpected feature is the negative sign of the
term. As close to the continuum limit as we can get (), we
obtain
We also compute several universal coupling constants and ratios, including
the combination of critical amplitudes .Comment: 13 pages, 5 Postscript figures, uses epsf.st
On details of the thermodynamical derivation of the Ginsburg--Landau equations
We examine the procedure of thermodynamical derivation of the
Ginsburg--Landau equation for current, which is given unclear and contradictory
interpretations in existing textbooks. We clarify all steps of this procedure
and find as a consequence a limitation on the validity range of the
thermodynamic Ginsburg--Landau theory, which does not seem to be explicitely
stated up to now: we conclude that the thermodynamic theory is applicable only
to a superconducting specimen that is not a part of an external
current-carrying loop.Comment: 11 pages. Accepted for publication in 'Superconductor Science and
Technology
Meson Synchrotron Emission from Central Engines of Gamma-Ray Bursts with Strong Magnetic Fields
Gamma-ray bursts (GRBs) are presumed to be powered by still unknown central
engines for the timescales in the range a few s. We propose that the
GRB central engines would be a viable site for strong meson synchrotron
emission if they were the compact astrophysical objects such as neutron stars
or rotating black holes with extremely strong magnetic fields and if protons or heavy nuclei were accelerated to ultra-relativistic
energies of order . We show that the charged scalar
mesons like and heavy vector mesons like , which have several
decay modes onto , could be emitted with high intensity a thousand
times larger than photons through strong couplings to ultra-relativistic
nucleons. These meson synchrotron emission processes eventually produce a burst
of very high-energy cosmic neutrinos with . These
neutrinos are to be detected during the early time duration of short GRBs.Comment: 12 pages, 4 figures. Accepted for publication in the Astrophysical
Journal Letter
Observation of Coherently-Enhanced Tunable Narrow-Band Terahertz Transition Radiation from a Relativistic Sub-Picosecond Electron Bunch Train
We experimentally demonstrate the production of narrow-band (% at THz) THz transition radiation with tunable
frequency over [0.37, 0.86] THz. The radiation is produced as a train of
sub-picosecond relativistic electron bunches transits at the vacuum-aluminum
interface of an aluminum converter screen. We also show a possible application
of modulated beams to extend the dynamical range of a popular bunch length
diagnostic technique based on the spectral analysis of coherent radiation.Comment: 3 pages, 6 figure
Vortex Origin of Tricritical Point in Ginzburg-Landau Theory
Motivated by recent experimental progress in the critical regime of
high- superconductors we show how the tricritical point in a
superconductor can be derived from the Ginzburg-Landau theory as a consequence
of vortex fluctuations. Our derivation explains why usual renormalization group
arguments always produce a first-order transition, in contrast to experimental
evidence and Monte Carlo simulations.Comment: 4 pages,1 figur
Bernoulli Potential, Hall Constant and Cooper Pairs Effective Masses in Disordered BCS Superconductors
It is analyzed what fundamental new information for the properties of the
superconductors can be obtained by systematic investigation of the Bernoulli
effect. It is shown that it is a tool to determine the effective mass of Cooper
pairs, the volume density of charge carriers, the temperature dependence of the
penetration depth and condensation energy. The theoretical results for
disordered and anisotropic gap superconductors are systematized for this aim.
For clean-anisotropic-gap superconductors is presented a simple derivation for
the temperature dependence of the penetration depthComment: 13 pages, 3 figures, LaTeX 2e, New figure and reference
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