23 research outputs found
Two-dimensional nonlocal vortices, multipole solitons and azimuthons in dipolar Bose-Einstein condensates
We have performed numerical analysis of the two-dimensional (2D) soliton
solutions in Bose-Einstein condensates with nonlocal dipole-dipole
interactions. For the modified 2D Gross-Pitaevski equation with nonlocal and
attractive local terms, we have found numerically different types of nonlinear
localized structures such as fundamental solitons, radially symmetric vortices,
nonrotating multisolitons (dipoles and quadrupoles), and rotating multisolitons
(azimuthons). By direct numerical simulations we show that these structures can
be made stable.Comment: 6 pages, 6 figures, submitted to Phys. Rev.
Two-dimensional ring-like vortex and multisoliton nonlinear structures at the upper-hybrid resonance
Two-dimensional (2D) equations describing the nonlinear interaction between
upper-hybrid and dispersive magnetosonic waves are presented. Nonlocal
nonlinearity in the equations results in the possibility of existence of stable
2D nonlinear structures. A rigorous proof of the absence of collapse in the
model is given. We have found numerically different types of nonlinear
localized structures such as fundamental solitons, radially symmetric vortices,
nonrotating multisolitons (two-hump solitons, dipoles and quadrupoles), and
rotating multisolitons (azimuthons). By direct numerical simulations we show
that 2D fundamental solitons with negative hamiltonian are stable.Comment: 8 pages, 6 figures, submitted to Phys. Plasma
Stabilization of higher-order vortices and multi-hump solitons in media with synthetic nonlocal nonlinearities
We address the evolution of higher-order excited states, such as vortex and
multi-hump solitons, in nonlocal media with synthetic, competing focusing and
defocusing nonlinearities with different nonlocal transverse scales. We reveal
that introduction of suitable competing effects makes possible the
stabilization of vortex solitons with topological charge m>2, as well as
one-dimensional multi-hump solitons with number of humps p>4, all of which are
highly unstable in natural nonlocal materials with focusing nonlinearities.Comment: 14 pages, 5 figures, to appear in Physical Review
Stabilization of dipole solitons in nonlocal nonlinear media
We address the stabilization of dipole solitons in nonlocal nonlinear
materials by two different approaches. First, we study the properties of such
solitons in thermal nonlinear media, where the refractive index landscapes
induced by laser beams strongly depend on the boundary conditions and on the
sample geometry. We show how the sample geometry impacts the stability of
higher-order solitons in thermal nonlinear media and reveal that dipole
solitons can be made dynami-cally stable in rectangular geometries in contrast
to their counterparts in thermal samples with square cross-section. Second, we
discuss the impact of the saturation of the nonlocal nonlinear response on the
properties of multipole solitons. We find that the saturable response also
stabi-lizes dipole solitons even in symmetric geometries, provided that the
input power exceeds a criti-cal value.Comment: 29 pages, 8 figures, to appear in Phys. Rev.
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
Stabilization of vector soliton complexes in nonlocal nonlinear media
We introduce vector soliton complexes in nonlocal Kerr-type nonlinear media.
We discover that under proper conditions the combination of nonlocality and
vectorial coupling has a remarkable stabilizing action on multi-humped
solitons. In particular, we find that stable bound states featuring several
field oscillations in each soliton component do exist. This affords
stabilization of vector soliton trains incorporating large number of humps, a
class of structures known to self-destroy via strong instabilities in scalar
settings.Comment: 17 pages, 4 figures, to appear in Physical Review E (Rapid
Communications
Stability of two-dimensional spatial solitons in nonlocal nonlinear media
We discuss existence and stability of two-dimensional solitons in media with
spatially nonlocal nonlinear response. We show that such systems, which include
thermal nonlinearity and dipolar Bose Einstein condensates, may support a
variety of stationary localized structures - including rotating spatial
solitons. We also demonstrate that the stability of these structures critically
depends on the spatial profile of the nonlocal response function.Comment: 8 pages, 9 figure
Primjena frakcijske plinske analize za određivanje sadržaja oksidnih i dušičnih faza u ALNICO legurama
Fractional gas analysis procedure for estimating the contents of oxide and nitride inclusions in Alnico alloys produced from wastes of production is developed. The effect of the temperature and time of melt holding before pouring on the content of impurity oxide and nitride inclusions is considered. The content of SiO2 inclusions in Alnico mainly depends on the holding time before pouring and decreases with increasing holding time, whereas the content of Al2O3 inclusions decreases with increasing both temperature and time of holding. The content of TiN inclusions decreases with increasing holding time. As the holding temperature increases, the content of nitride inclusions decreases only with increasing holding time.Razrađena je metoda frakcijske plinske analize za vrednovanje oksidnih i dušičnih uključaka u ALNICO legurama, dobijenih iz gospodarskih otpada. Posmatran je utjecaj temperature i vremena zadržavanja kupke prije lijevanja. Sadržaj uključaka SiO2 uglavnom ovisi od vremena zadrške prije lijevanja i snižava se povećanjem tog vremena, istodobno se sadržaj uključaka Al2O3 smanjuje s povećavanjem i temperature i vremena zadrške. Sadržaj uključaka TiN smanjuje se povećavanjem vremena zadrške. S povećanjem temperature sadržaj dušičnih uključaka smanjuje se samo pri povećanju vremena zadrške prije lijevanja
Fractional gas analysis procedure for determining the contents of oxide and nitride phases in ALNICO alloys
Fractional gas analysis procedure for estimating the contents of oxide and nitride inclusions in Alnico alloys produced from wastes of production is developed. The effect of the temperature and time of melt holding before pouring on the content of impurity oxide and nitride inclusions is considered. The content of SiO2 inclusions in Alnico mainly depends on the holding time before pouring and decreases with increasing holding time, whereas the content of Al2O3 inclusions decreases with increasing both temperature and time of holding. The content of TiN inclusions decreases with increasing holding time. As the holding temperature increases, the content of nitride inclusions decreases only with increasing holding time