28,008 research outputs found
Analytical study of coherence in seeded modulation instability
We derive analytical expressions for the coherence in the onset of modulation
instability, in excellent agreement with thorough numerical simulations. As
usual, we start by a linear perturbation analysis, where broadband noise is
added to a continuous wave (CW) pump; then, we investigate the effect of adding
a deterministic seed to the CW pump, a case of singular interest as it is
commonly encountered in parametric amplification schemes. Results for the
dependence of coherence on parameters such as fiber type, pump power,
propagated distance, seed signal-to-noise ratio are presented. Finally, we show
the importance of including higher-order linear and nonlinear dispersion when
dealing with generation in longer wavelength regions (mid IR). We believe these
results to be of relevance when applied to the analysis of the coherence
properties of supercontinua generated from CW pumps.Comment: 6 pages, 8 figure
Magneto-optical imaging of magnetic deflagration in Mn12-Acetate
For the first time, the morphology and dynamics of spin avalanches in
Mn12-Acetate crystals using magneto-optical imaging has been explored. We
observe an inhomogeneous relaxation of the magnetization, the spins reversing
first at one edge of the crystal and a few milliseconds later at the other end.
Our data fit well with the theory of magnetic deflagration, demonstrating that
very slow deflagration rates can be obtained, which makes new types of
experiments possible.Comment: 5 two-column pages, 3 figures, EPL styl
Collins functions for pions from SIDIS and new e+e- data: a first glance at their transverse momentum dependence
New data from Belle and BaBar Collaborations on azimuthal asymmetries,
measured in e+e- annihilations into pion pairs at Q^2=112 GeV^2, allow to take
the first, direct glance at the transverse momentum dependence of the Collins
functions, in addition to their z dependence. These data, together with
available Semi-Inclusive Deep Inelastic Scattering (SIDIS) data on the Collins
asymmetry, are simultaneously analysed in the framework of the generalised
parton model assuming two alternative Q^2 evolution schemes and exploiting two
different parameterisations for the Collins functions. The corresponding
results for the transversity distributions are presented. Analogous data, newly
released by the BESIII Collaboration, on e+e- annihilations into pion pairs at
the lower Q^2 of 13 GeV^2, offer the possibility to explore the sensitivity of
these azimuthal correlations on transverse momentum dependent evolution
effects.Comment: 20 pages, 15 figures, 4 table
On the Integrability of the Discrete Nonlinear Schroedinger Equation
In this letter we present an analytic evidence of the non-integrability of
the discrete nonlinear Schroedinger equation, a well-known discrete evolution
equation which has been obtained in various contexts of physics and biology. We
use a reductive perturbation technique to show an obstruction to its
integrability.Comment: 4 pages, accepted in EP
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