198 research outputs found
See-Saw Energy Scale and the LSND Anomaly
The most general, renormalizable Lagrangian that includes massive neutrinos
contains ``right-handed neutrino'' Majorana masses of order M. While there are
prejudices in favor of M much larger than the weak scale, virtually nothing is
known about the magnitude of M. I argue that the LSND anomaly provides,
currently, the only experimental hint: M around 1 eV. If this is the case, the
LSND mixing angles are functions of the active neutrino masses and mixing and,
remarkably, adequate fits to all data can be naturally obtained. I also discuss
consequences of this ``eV-seesaw'' for supernova neutrino oscillations, tritium
beta-decay, neutrinoless double-beta decay, and cosmology.Comment: revtex, 4 pages, no figure
Multichannel oscillations and relations between LSND, KARMEN and MiniBooNE, with and without CP violation
We show by examples that multichannel mixing can affect both the parameters
extracted from neutrino oscillation experiments, and that more general
conclusions derived by fitting the experimental data under the assumption that
only two channels are involved in the mixing. Implications for MiniBooNE are
noted and an example based on maximal CP violation displays profound
implications for the two data sets (muon-neutrino and muon-antineutrino) of
that experiment.Comment: 5 pages 4 figure
Nonlocal stabilization of nonlinear beams in a self-focusing atomic vapor
We show that ballistic transport of optically excited atoms in an atomic
vapor provides a nonlocal nonlinearity which stabilizes the propagation of
vortex beams and higher order modes in the presence of a self-focusing
nonlinearity. Numerical experiments demonstrate stable propagation of lowest
and higher order vortices over a hundred diffraction lengths, before
dissipation leads to decay of these structures.Comment: 3 figure
Rotating soliton solutions in nonlocal nonlinear media
We discuss generic properties of rotating nonlinear wave solutions, the so
called azimuthons, in nonlocal media. Variational methods allow us to derive
approximative values for the rotating frequency, which is shown to depend
crucially on the nonlocal response function. Further on, we link families of
azimuthons to internal modes of classical non-rotating stationary solutions,
namely vortex and multipole solitons. This offers an exhaustive method to
identify azimuthons in a given nonlocal medium.Comment: 14 pages, 9 figures, 3 movies (external links
Scattering of dipole-mode vector solitons: Theory and experiment
We study, both theoretically and experimentally, the scattering properties of
optical dipole-mode vector solitons - radially asymmetric composite
self-trapped optical beams. First, we analyze the soliton collisions in an
isotropic two-component model with a saturable nonlinearity and demonstrate
that in many cases the scattering dynamics of the dipole-mode solitons allows
us to classify them as ``molecules of light'' - extremely robust spatially
localized objects which survive a wide range of interactions and display many
properties of composite states with a rotational degree of freedom. Next, we
study the composite solitons in an anisotropic nonlinear model that describes
photorefractive nonlinearities, and also present a number of experimental
verifications of our analysis.Comment: 8 pages + 4 pages of figure
Modulational instability, solitons and beam propagation in spatially nonlocal nonlinear media
We present an overview of recent advances in the understanding of optical
beams in nonlinear media with a spatially nonlocal nonlinear response. We
discuss the impact of nonlocality on the modulational instability of plane
waves, the collapse of finite-size beams, and the formation and interaction of
spatial solitons.Comment: Review article, will be published in Journal of Optics B, special
issue on Optical Solitons, 6 figure
Two dimensional modulational instability in photorefractive media
We study theoretically and experimentally the modulational instability of
broad optical beams in photorefractive nonlinear media. We demonstrate the
impact of the anisotropy of the nonlinearity on the growth rate of periodic
perturbations. Our findings are confirmed by experimental measurements in a
strontium barium niobate photorefractive crystal.Comment: 8 figure
Interaction of matter-wave gap solitons in optical lattices
We study mobility and interaction of gap solitons in a Bose-Einstein
condensate (BEC) confined by an optical lattice potential. Such localized
wavepackets can exist only in the gaps of the matter-wave band-gap spectrum and
their interaction properties are shown to serve as a measure of discreteness
imposed onto a BEC by the lattice potential. We show that inelastic collisions
of two weakly localized near-the-band-edge gap solitons provide simple and
effective means for generating strongly localized in-gap solitons through
soliton fusion.Comment: 12 pages, 7 figure
Nonlocal description of X waves in quadratic nonlinear materials
We study localized light bullets and X waves in quadratic media and show how the notion of nonlocality can provide an alternative simple physical picture of both types of multidimensional nonlinear waves. For X waves we show that a local cascading limit in terms of a nonlinear Schrödinger equation does not exist—one needs
to use the nonlocal description, because the nonlocal response function does not converge toward a function.
Also, we use the nonlocal theory to show that the coupling to the second harmonic is able to generate an X shape in the fundamental field despite having anomalous dispersion, in contrast to the predictions of the cascading limit
The theory of optical dispersive shock waves in photorefractive media
The theory of optical dispersive shocks generated in propagation of light
beams through photorefractive media is developed. Full one-dimensional
analytical theory based on the Whitham modulation approach is given for the
simplest case of sharp step-like initial discontinuity in a beam with
one-dimensional strip-like geometry. This approach is confirmed by numerical
simulations which are extended also to beams with cylindrical symmetry. The
theory explains recent experiments where such dispersive shock waves have been
observed.Comment: 26 page
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