152,884 research outputs found
Decay of weak turbulence
Weak turbulence fields generated by single and multiple stage grids covering Reynolds numbers between 7 and 70 showing decay of energy spectr
GRB afterglows: deep Newtonian phase and its application
Gamma-ray burst afterglows have been observed for months or even years in a
few cases. It deserves noting that at such late stages, the remnants should
have entered the deep Newtonian phase, during which the majority of
shock-accelerated electrons will no longer be highly relativistic. To calculate
the afterglows, we must assume that the electrons obey a power-law distribution
according to their kinetic energy, not simply the Lorentz factor.Comment: Poster at the 4th workshop "Gamma-Ray Bursts in the Afterglow Era"
(Rome, 2004), accepted for publication in the proceedings. 4 pages, with 3
figures inserte
Implications of the non-universal Z boson in FCNC mediated rare decays
We analyze the effect of the non-universal boson in the rare decays , and decays. These
decays involve the FCNC mediated transitions, and are found to be
very small in the standard model. The smallness of these decays in the standard
model makes them sensitive probe for new physics. We find an enhancement of at
least an order in these branching ratios because of the non-universal
coupling.Comment: 15 pages, 4 figures, minor changes in the text, references added, to
appear in PR
Beaming effects in GRBs and orphan afterglows
The overall dynamical evolution and radiation mechanism of -ray burst
jets are briefly introduced. Various interesting topics concerning beaming in
-ray bursts are discussed, including jet structures, orphan afterglows
and cylindrical jets. The possible connection between -ray bursts and
neutron star kicks is also addressed.Comment: 10 Pages, 4 figures, to appear in a special issue of ApSS. Oral
report presented at "The Multiwavelength Approach to Unidentified Gamma-Ray
Sources" (Hong Kong, June 1 - 4, 2004; Conference organizers: K.S. Cheng and
G.E. Romero
The Electric Dipole Moment and CP Violation in in SUGRA Models with Nonuniversal Gaugino Masses
The constraints of electric dipole moments (EDMs) of electron and neutron on
the parameter space in supergravity (SUGRA) models with nonuniversal gaugino
masses are analyzed. It is shown that with a light sparticle spectrum, the
sufficient cancellations in the calculation of EDMs can happen for all phases
being order of one in the small tan case and all phases but
() order of one in the large tan case. This is
in contrast to the case of mSUGRA in which in the parameter space where
cancellations among various SUSY contributions to EDMs happen
must be less than for small and for
large . Direct CP asymmetries and the T-odd polarization of lepton in
are investigated in the models. In the large tan case,
and for l= () can be enhanced by about a factor of
ten (ten) and ten (three) respectively compared to those of mSUGRA.Comment: 12 pages, latex, 4 figures, a few change
Negative refraction and plano-concave lens focusing in one-dimensional photonic crystals
Negative refraction is demonstrated in one-dimensional (1D) dielectric
photonic crystals (PCs) at microwave frequencies. Focusing by plano-concave
lens made of 1D PC due to negative refraction is also demonstrated. The
frequency-dependent negative refractive indices, calculated from the
experimental data matches very well with those determined from band structure
calculations. The easy fabrication of one-dimensional photonic crystals may
open the door for new applications.Comment: 3 pages and 5 figure
Modeling Vacuum Arcs
We are developing a model of vacuum arcs. This model assumes that arcs
develop as a result of mechanical failure of the surface due to Coulomb
explosions, followed by ionization of fragments by field emission and the
development of a small, dense plasma that interacts with the surface primarily
through self sputtering and terminates as a unipolar arc capable of producing
breakdown sites with high enhancement factors. We have attempted to produce a
self consistent picture of triggering, arc evolution and surface damage. We are
modeling these mechanisms using Molecular Dynamics (mechanical failure, Coulomb
explosions, self sputtering), Particle-In-Cell (PIC) codes (plasma evolution),
mesoscale surface thermodynamics (surface evolution), and finite element
electrostatic modeling (field enhancements). We can present a variety of
numerical results. We identify where our model differs from other descriptions
of this phenomenon.Comment: 4 pages, 5 figure
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