6,725 research outputs found
Mixed symmetry localized modes and breathers in binary mixtures of Bose-Einstein condensates in optical lattices
We study localized modes in binary mixtures of Bose-Einstein condensates
embedded in one-dimensional optical lattices. We report a diversity of
asymmetric modes and investigate their dynamics. We concentrate on the cases
where one of the components is dominant, i.e. has much larger number of atoms
than the other one, and where both components have the numbers of atoms of the
same order but different symmetries. In the first case we propose a method of
systematic obtaining the modes, considering the "small" component as
bifurcating from the continuum spectrum. A generalization of this approach
combined with the use of the symmetry of the coupled Gross-Pitaevskii equations
allows obtaining breather modes, which are also presented.Comment: 11 pages, 16 figure
Hypercubic effects in semileptonic decays of heavy mesons, toward , with Twisted fermions
We present a preliminary study toward a lattice determination of the vector
and scalar form factors of the semileptonic decays. We
compute the form factors relative to the transition between heavy-light
pseudoscalar mesons, with masses above the physical D-mass, and the pion. We
simulate heavy-quark masses in the range .
Lorentz symmetry breaking due to hypercubic effects is clearly observed in the
data, and included in the decomposition of the current matrix elements in terms
of additional form factors. We discuss the size of this breaking as the
parent-meson mass increases. Our analysis is based on the gauge configurations
produced by the European Twisted Mass Collaboration with
flavors of dynamical quarks at three different values of the lattice spacing
and with pion masses as small as MeV.Comment: 7 pages, 5 figures; contribution to the XXXVI International Symposium
on Lattice Field Theory (LATTICE2018), East Lansing (Michigan State
University, USA), July 22-28, 201
Shock waves in one-dimensional Heisenberg ferromagnets
We use SU(2) coherent state path integral formulation with the stationary
phase approximation to investigate, both analytically and numerically, the
existence of shock waves in the one- dimensional Heisenberg ferromagnets with
anisotropic exchange interaction. As a result we show the existence of shock
waves of two types,"bright" and "dark", which can be interpreted as moving
magnetic domains.Comment: 10 pages, with 3 ps figure
Adiabatic Compression of Soliton Matter Waves
The evolution of atomic solitary waves in Bose-Einstein condensate (BEC)
under adiabatic changes of the atomic scattering length is investigated. The
variations of amplitude, width, and velocity of soliton are found for both
spatial and time adiabatic variations. The possibility to use these variations
to compress solitons up to very high local matter densities is shown both in
absence and in presence of a parabolic confining potential.Comment: to appear in J.Phys.
The Effect of Structural Damping on the Forced Vibrations of Cylindrical Sandwich Shells
One has a polymeric, the other an elastomeric core. The results indicate that for the assumed conditions they are both effective for suppressing resonant-vibration, the polymeric core being generally more effective than the elastomeric core
On dissipationless shock waves in a discrete nonlinear Schr\"odinger equation
It is shown that the generalized discrete nonlinear Schr\"odinger equation
can be reduced in a small amplitude approximation to the KdV, mKdV, KdV(2) or
the fifth-order KdV equations, depending on values of the parameters. In
dispersionless limit these equations lead to wave breaking phenomenon for
general enough initial conditions, and, after taking into account small
dispersion effects, result in formation of dissipationless shock waves. The
Whitham theory of modulations of nonlinear waves is used for analytical
description of such waves.Comment: 15 pages, 9 figure
Tensor form factor of and decays with twisted-mass fermions
We present the first lattice Nf=2+1+1 determination of the tensor form factor
corresponding to the semileptonic and rare
decays as a function of the squared 4-momentum transfer . Together with
our recent determination of the vector and scalar form factors we complete the
set of hadronic matrix elements regulating the semileptonic and rare transitions within and beyond the Standard Model, when a non-zero
tensor coupling is possible. Our analysis is based on the gauge configurations
produced by ETMC with Nf=2+1+1 flavors of dynamical quarks, which include in
the sea, besides two light mass-degenerate quarks, also the strange and charm
quarks with masses close to their physical values. We simulated at three
different values of the lattice spacing and with pion masses as small as 220
MeV. The matrix elements of the tensor current are determined for plenty of
kinematical conditions in which parent and child mesons are either moving or at
rest. As in the case of the vector and scalar form factors, Lorentz symmetry
breaking due to hypercubic effects is clearly observed also in the data for the
tensor form factor and included in the decomposition of the current matrix
elements in terms of additional form factors. After the extrapolations to the
physical pion mass and to the continuum and infinite volume limits we determine
the tensor form factor in the whole kinematical region accessible in the
experiments. A set of synthetic data points, representing our results for
for several selected values of , is provided and the
corresponding covariance matrix is also available. At zero four-momentum
transfer we get and ,
which correspond to and .Comment: 22 pages, 7 figures, 10 tables. Conclusions unchanged. Version to
appear in PRD. arXiv admin note: text overlap with arXiv:1710.07121 and
substantial text overlap with arXiv:1706.0301
Nonreciprocal transmission of microwaves through a long Josephson junction
Nonreciprocal microwave transmission through a long Josephson junction in the
flux-flow regime is studied analytically and numerically within the framework
of the perturbed sine-Gordon model. We demonstrate that the maximum attenuation
of the transmitted power occurs when the direction of the flux flow is opposite
to the direction of the microwave propagation. This attenuation is
nonreciprocal with respect to the flux-flow direction and can be enhanced by
increasing the system length and proper impedance matching of the junction ends
to external transmission line.Comment: 5 pages, 5 figure
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