9,454 research outputs found
Compression of ultrashort UV pulses in a self-defocusing gas
Compression of UV femtosecond laser pulses focused into a gas cell filled
with xenon is reported numerically. With a large negative Kerr index and normal
dispersion, xenon promotes temporal modulational instability (MI) which can be
monitored to shorten ~ 100 fs pulses to robust, singly-peaked waveforms
exhibiting a fourfold compression factor. Combining standard MI theory with a
variational approach allows us to predict the beam parameters suitable for
efficient compression. At powers < 30 MW, nonlinear dispersion is shown to
shift the pulse temporal profile to the rear zone.Comment: 4 pages, 4 figure
A new color change to improve the coloring of a graph
AbstractFor some special classes of graphs an optimal coloring can be obtained by the âKempe methodâ: color as many vertices as possible with q given colors, and then make one of these colors available for an uncolored vertex x0 by interchanging the two colors of a âbicolor componentâ. It is well known that in general these interchanges cannot lead to an optimal coloring.We shall define here another type of color changes which can always lead to an optimal coloring. The basic tool is the concept of an âodd alternating sequenceâ
Fuzzy Bigraphs: An Exercise in Fuzzy Communicating Agents
Bigraphs and their algebra is a model of concurrency. Fuzzy bigraphs are a
generalization of birgraphs intended to be a model of concurrency that
incorporates vagueness. More specifically, this model assumes that agents are
similar, communication is not perfect, and, in general, everything is or
happens to some degree.Comment: 11 pages, 3 figure
q_T Uncertainties for W and Z Production
Analysis of semi-inclusive DIS hadroproduction suggests broadening of
transverse momentum distributions at small x below 1E-3 ~ 1E-2 which can be
modeled in the Collins-Soper-Sterman formalism by a modification of impact
parameter dependent parton densities. We investigate these consequences for the
production of electroweak bosons at the Tevatron and the LHC. If substantial
small-x broadening is observed in forward Z boson production in the Tevatron
Run-2, it will strongly affect the predicted q_T distributions for W and Z
boson production at the LHC.Comment: 4 pages, 2 figures; contribution to the XIII International Workshop
on Deep Inelastic Scattering (DIS 2005
Natural linewidth analysis of d-band photoemission from Ag(110)
We report a high-resolution angle-resolved study of photoemission linewidths
observed for Ag(110). A careful data analysis yields kdd\tau_h \geq 22
d$-hole dynamics in Cu (I.\
Campillo et al., Phys. Rev. Lett., in press) we interpret the lifetime
enhancement by a small scattering cross-section of - and -states below
the Fermi level. With increasing distance to the -hole lifetimes get
shorter because of the rapidly increasing density of d-states and contributions
of intra--band scattering processes, but remain clearly above
free-electron-model predictions.Comment: 14 pages, 7 figure
A combinatorial problem in logic
AbstractThis short note is an application of some theorems of graph theory to the problem of the minimum number of counter-examples needed to show that a special class of theories is complete
Vestigial structures in pontoporeiid and stegocephalid amphipods (Crustacea, Amphipoda, Gammaridea)
Neutrino-Nucleus Cross Section Measurements using Stopped Pions and Low Energy Beta Beams
Two new facilities have recently been proposed to measure low energy
neutrino-nucleus cross sections, the nu-SNS (Spallation Neutron Source) and low
energy beta beams. The former produces neutrinos by pion decay at rest, while
the latter produces neutrinos from the beta decays of accelerated ions. One of
the uses of neutrino-nucleus cross section measurements is for supernova
studies, where typical neutrino energies are 10s of MeV. In this energy range
there are many different components to the nuclear response and this makes the
theoretical interpretation of the results of such an experiment complex.
Although even one measurement on a heavy nucleus such as lead is much
anticipated, more than one data set would be still better. We suggest that this
can be done by breaking the electron spectrum down into the parts produced in
coincidence with one or two neutrons, running a beta beam at more than one
energy, comparing the spectra produced with pions and a beta beam or any
combination of these.Comment: 6 pages, 6 figure
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