5,772 research outputs found
Sterile neutrinos in neutrinoless double beta decay
We study possible contribution of the Majorana neutrino mass eigenstate
dominated by a sterile neutrino component to neutrinoless double beta
() decay. From the current experimental lower bound on the
-decay half-life of Ge we derive stringent constraints
on the mixing in a wide region of the values of mass. We
discuss cosmological and astrophysical status of in this mass region.Comment: 6 pages, 1 figure; v2 added comments and reference
Rotating three-dimensional solitons in Bose Einstein condensates with gravity-like attractive nonlocal interaction
We study formation of rotating three-dimensional high-order solitons
(azimuthons) in Bose Einstein condensate with attractive nonlocal nonlinear
interaction. In particular, we demonstrate formation of toroidal rotating
solitons and investigate their stability. We show that variational methods
allow a very good approximation of such solutions and predict accurately the
soliton rotation frequency. We also find that these rotating localized
structures are very robust and persist even if the initial condensate
conditions are rather far from the exact soliton solutions. Furthermore, the
presence of repulsive contact interaction does not prevent the existence of
those solutions, but allows to control their rotation. We conjecture that
self-trapped azimuthons are generic for condensates with attractive nonlocal
interaction
Limits to compression with cascaded quadratic soliton compressors
We study cascaded quadratic soliton compressors and address the physical
mechanisms that limit the compression. A nonlocal model is derived, and the
nonlocal response is shown to have an additional oscillatory component in the
nonstationary regime when the group-velocity mismatch (GVM) is strong. This
inhibits efficient compression. Raman-like perturbations from the cascaded
nonlinearity, competing cubic nonlinearities, higher-order dispersion, and
soliton energy may also limit compression, and through realistic numerical
simulations we point out when each factor becomes important. We find that it is
theoretically possible to reach the single-cycle regime by compressing
high-energy fs pulses for wavelengths in a
-barium-borate crystal, and it requires that the system is in the
stationary regime, where the phase mismatch is large enough to overcome the
detrimental GVM effects. However, the simulations show that reaching
single-cycle duration is ultimately inhibited by competing cubic nonlinearities
as well as dispersive waves, that only show up when taking higher-order
dispersion into account.Comment: 16 pages, 5 figures, submitted to Optics Expres
Photoemission studies of the noble metals, the cuprous halides, and selected alkali halides
Photoemission studies of noble metals, cuprous halides, and alkali halide
Pattern formation in the nonlinear Schrödinger equation with competing nonlocal nonlinearities
We study beam propagation in the framework of the nonlinear Schrödinger equation with competing Gaussian nonlocal nonlinearities. We demonstrate that such system can give rise to self-organization of light into stable states of trains or hexagonal arrays of filaments, depending on the transverse dimensionality. This long-range ordering can be achieved by mere unidirectional beam propagation. We discuss the dynamics of long-range ordering and the crucial role which the phase of the wavefunction plays for this phenomenon. Furthermore we discuss how transverse dimensionality affects the order of the phasetransition
Constraining Mass Spectra with Sterile Neutrinos from Neutrinoless Double Beta Decay, Tritium Beta Decay and Cosmology
We analyze the constraints on neutrino mass spectra with extra sterile
neutrinos as implied by the LSND experiment. The various mass related
observables in neutrinoless double beta decay, tritium beta decay and cosmology
are discussed. Both neutrino oscillation results as well as recent cosmological
neutrino mass bounds are taken into account. We find that some of the allowed
mass patterns are severely restricted by the current constraints, in particular
by the cosmological constraints on the total sum of neutrino masses and by the
non-maximality of the solar neutrino mixing angle. Furthermore, we estimate the
form of the four neutrino mass matrices and also comment on the situation in
scenarios with two additional sterile neutrinos.Comment: 40 pages, 9 figures. Minor changes, matches version in PR
Collapse in the nonlocal nonlinear Schr\"odinger equation
We discuss spatial dynamics and collapse scenarios of localized waves
governed by the nonlinear Schr\"{o}dinger equation with nonlocal nonlinearity.
Firstly, we prove that for arbitrary nonsingular attractive nonlocal nonlinear
interaction in arbitrary dimension collapse does not occur. Then we study in
detail the effect of singular nonlocal kernels in arbitrary dimension using
both, Lyapunoff's method and virial identities. We find that for for a
one-dimensional case, i.e. for , collapse cannot happen for nonlocal
nonlinearity. On the other hand, for spatial dimension and singular
kernel , no collapse takes place if , whereas
collapse is possible if . Self-similar solutions allow us to find
an expression for the critical distance (or time) at which collapse should
occur in the particular case of kernels. Moreover, different
evolution scenarios for the three dimensional physically relevant case of Bose
Einstein condensate are studied numerically for both, the ground state and a
higher order toroidal state with and without an additional local repulsive
nonlinear interaction. In particular, we show that presence of an additional
local repulsive term can prevent collapse in those cases
Quadratic solitons as nonlocal solitons
We show that quadratic solitons are equivalent to solitons of a nonlocal Kerr
medium. This provides new physical insight into the properties of quadratic
solitons, often believed to be equivalent to solitons of an effective saturable
Kerr medium. The nonlocal analogy also allows for novel analytical solutions
and the prediction of novel bound states of quadratic solitons.Comment: 4 pages, 3 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
Singlet Fermionic Dark Matter explains DAMA signal
It has been suggested that, considering channeling effect, the order of a few
GeV dark matters which are elastically scattered from detector nuclei might be
plausible candidates reconciling the DAMA annual modulation signal with the
results of other null experiments. We show that Singlet Fermionic Dark Matter
can be such a dark matter candidate, simultaneously providing the correct
thermal relic density which is consistent with the WMAP data.Comment: 9 pages, 3 figure
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