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

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

Improvement of Vitis vinifera sativa D. C. taxonomy

A method of mathematical statistics for evaluation of the taxonomic usefulness of characters included in the Vitis vinifera sativa D. C. cultivar clustering has been developed. The method works as follows: The irregularity of the distribution of characters in taxons is calculated, and the probability of achieving such estimates is calculated when all taxons are assigned to the same general population after a certain character. The method does not depend on the type of the distribution of characters and is computer-programmed (a CM-4 computer). Using the method, it is possible to conclude that the higher the taxon hierarchy, the smaller is the amount of taxonomically useful characters the taxons differ in, i.e. in order to differentiate taxons of lower hierarchy a smaller amount of descriptive characters is necessary. Var. transcaucasica and var. mediiasica have been isolated in the taxon convar. orientalis subconvar. caspica NEGR. and in the taxon subconvar. antasiatica NEGFL, while the taxon convar. pontica NEGR has been supplemented with subconvar. meridionali-balcanica and georgica-caspica along with subconvar. balcanica and georgica NEGR. Using discriminant analysis, assignment of many cultivars to proper taxons has been verified. The phenogenetic proximity of taxons has been established. Some problems of the theory of evolution and those of practical breeding are discussed

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

On radiative damping in plasma-based accelerators

Radiative damping in plasma-based electron accelerators is analyzed. The electron dynamics under combined influence of the constant accelerating force and the classical radiation reaction force is studied. It is shown that electron acceleration cannot be limited by radiation reaction. If initially the accelerating force was stronger than the radiation reaction force then the electron acceleration is unlimited. Otherwise the electron is decelerated by radiative damping up to a certain instant of time and then accelerated without limits. Regardless of the initial conditions the infinite-time asymptotic behavior of an electron is governed by self-similar solution providing unlimited acceleration. The relative energy spread induced by the radiative damping decreases with time in the infinite-time limit

Soliton Molecules In Dipolar Bose-Einstein Condensates

Dipolar interactions support the formation of inter-site soliton molecules in a stack of quasi-1D traps. We show that the stability and properties of individual solitons, and soliton molecules in such a geometry crucially depend on the interplay between contact and dipolar interactions. In particular, two different quasi-1D soliton regimes are possible: a 1D soliton characterized by purely repulsive DDI and a 3D soliton for which a sufficiently large dipole moment renders the DDI attractive. Furthermore, we find that contrary to the case of dimers of polar molecules, the soliton dimers exhibit a nontrivial behavior of the elementary excitations that stems from the competition between on-site and inter-site DDI. Finally, we prove the existence of soliton trimers in a regime where molecular trimers do not occur. We demonstrate that the soliton molecules that we report are well feasible under realistic experimental conditions

A new regime of anomalous penetration of relativistically strong laser radiation into an overdense plasma

It is shown that penetration of relativistically intense laser light into an overdense plasma, accessible by self-induced transparency, occurs over a finite length only. The penetration length depends crucially on the overdense plasma parameter and increases with increasing incident intensity after exceeding the threshold for self-induced transparency. Exact analytical solutions describing the plasma-field distributions are presented.Comment: 6 pages, 2 figures in 2 separate eps files; submitted to JETP Letter