121 research outputs found
Adsorption of a random heteropolymer with self-interactions onto an interface
We consider the adsorption of a random heteropolymer onto an interface within
the model by Garel et al. [1] by taking into account self-interactions between
the monomers. Within the replica trick and by using a self-consistent
preaveraging procedure we map the adsorption problem onto the problem of
binding state of a quantum mechanical Hamiltonian. The analysis of the latter
is treated within the variational method based on the 2-nd Legendre transform.
We have found that self-interactions favor the localization. The effect is
intensified with decrease of the temperature. Within a model without taking
into account the repulsive ternary monomer-monomer interactions we predict a
reentrant localization transition for large values of the asymmetry of the
heteropolymer and at low enough temperatures.Comment: 11 pages, 3 figure
Scattering of gap solitons by PT-symmetric defects
The resonant scattering of gap solitons (GS) of the periodic nonlinear
Schr\"odinger equation with a localized defect which is symmetric under the
parity and the time-reversal (PT) symmetry, is investigated. It is shown that
for suitable amplitudes ratios of the real and imaginary parts of the defect
potential the resonant transmission of the GS through the defect becomes
possible. The resonances occur for potential parameters which allow the
existence of localized defect modes with the same energy and norm of the
incoming GS. Scattering properties of GSs of different band-gaps with effective
masses of opposite sign are investigated. The possibility of unidirectional
transmission and blockage of GSs by PT defect, as well as, amplification and
destruction induced by multiple reflections from two PT defects, are also
discussed
Dynamical generation of interwoven soliton trains by nonlinear emission in binary Bose-Einstein condensates
We propose a method for the generation of trains of alternating bright
solitons in two-component Bose-Einstein condensates, using controlled emission
of nonlinear matter-waves in the uncoupled regime with spatially-varying
intra-species interaction and out-of-phase oscillations of the ground states in
the trap. Under this scheme, solitons are sequentially launched from the
different components, and interact with each other through phase-independent
cross-coupling. We obtain an analytical estimation of the critical condition
for soliton emission using a geometric guiding model, in analogy with
integrated optical systems. In addition, we show how strong initial
perturbations in the system can trigger the spontaneous generation of
supersolitons, i.e. localized phonon-like excitations of the soliton trains.
Finally, we demonstrate the controllable generation of slow and fast
supersolitons by adding external localized potentials in the nonlinear region
Dragging two-dimensional discrete solitons by moving linear defects
We study the mobility of small-amplitude solitons attached to moving defects
which drag the solitons across a two-dimensional (2D) discrete
nonlinear-Schr\"{o}dinger (DNLS) lattice. Findings are compared to the
situation when a free small-amplitude 2D discrete soliton is kicked in the
uniform lattice. In agreement with previously known results, after a period of
transient motion the free soliton transforms into a localized mode pinned by
the Peierls-Nabarro potential, irrespective of the initial velocity. However,
the soliton attached to the moving defect can be dragged over an indefinitely
long distance (including routes with abrupt turns and circular trajectories)
virtually without losses, provided that the dragging velocity is smaller than a
certain critical value. Collisions between solitons dragged by two defects in
opposite directions are studied too. If the velocity is small enough, the
collision leads to a spontaneous symmetry breaking, featuring fusion of two
solitons into a single one, which remains attached to either of the two
defects
Dynamics of matter solitons in weakly modulated optical lattices
It is shown that matter solitons can be effectively managed by means of
smooth variations of parameters of optical lattices in which the condensate is
loaded. The phenomenon is based on the effect of lattice modulations on the
carrier wave transporting the soliton and that is why is well understood in
terms of the effective mass approach, where a particular spatial configuration
of the band structure is of primary importance. Linear, parabolic, and
spatially localized modulations are considered as the case examples. It is
shown that these defects can originate accelerating and oscillating motion of
matter solitons as well as simulate soliton interaction with attractive and
repulsive defects.Comment: 6 pages, 7 figures (text with major revision
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