Controllable soliton emission from a Bose-Einstein condensate

We demonstrate, through numerical simulations, the controllable emission of matter-wave bursts from a Bose-Einstein Condensate in a shallow optical dipole trap. The process is triggered by spatial variations of the scattering length along the trapping axis. In our approach, the outcoupling mechanism are atom-atom interactions and thus, the trap remains unaltered. Once emitted, the matter wave forms a robust soliton. We calculate analytically the parameters for the experimental implementation of this atomic soliton machine gun.Comment: 4 pages, 5 figure

Stable topological modes in two-dimensional Ginzburg-Landau models with trapping potentials

Complex Ginzburg-Landau (CGL) models of laser media (with the cubic-quintic nonlinearity) do not contain an effective diffusion term, which makes all vortex solitons unstable in these models. Recently, it has been demonstrated that the addition of a two-dimensional periodic potential, which may be induced by a transverse grating in the laser cavity, to the CGL equation stabilizes compound (four-peak) vortices, but the most fundamental "crater-shaped" vortices (CSVs), alias vortex rings, which are, essentially, squeezed into a single cell of the potential, have not been found before in a stable form. In this work we report families of stable compact CSVs with vorticity S=1 in the CGL model with the external potential of two different types: an axisymmetric parabolic trap, and the periodic potential. In both cases, we identify stability region for the CSVs and for the fundamental solitons (S=0). Those CSVs which are unstable in the axisymmetric potential break up into robust dipoles. All the vortices with S=2 are unstable, splitting into tripoles. Stability regions for the dipoles and tripoles are identified too. The periodic potential cannot stabilize CSVs with S>=2 either; instead, families of stable compact square-shaped quadrupoles are found

AGROCHEMICAL STUDY IN THE AREA OF SILIȘTEA-GUMEȘTI TELEORMAN COUNTY, WITH AN AREA OF 210 HA, WITH THE PURPOSE OF ELABORATING THE FERTILIZATION PLAN ON CROPS

In order to carry out this study, work was carried out on the morphological, physical and chemical characterization, determining the productive potential of the soil cover, enunciating the measures of soil improvement and elaborating the fertilization plan on crops. The field stage includes the presentation of general and local ecopedological conditions. In this regard, observations were made on the territory from the point of view of each ecopedological factor. Based on the movement on the ground, observations were made on the micro-relief, the level of the groundwater, the vegetation and the degree of anthropization of the soil cover following the mobilization, preparation of the germination bed and current maintenance. The soil samples were collected according to the cadastral plan, with an area of 210 ha being located on the radius of SilișteaGumești commune, Teleorman county. For the characterization of the soil cover from the above mentioned surface, a soil profile and a few surveys were carried out, in order to correctly identify the representative soil type. Also, agrochemical mapping was performed, 44 soil samples were collected from the arable horizon (0-20 cm) in disturbed system (in plastic bags). The description of the pedogenetic conditions and the soil cover from soil boiling, was carried out according to the "Guide for the description in the field of the soil profile and the specific environmental conditions", authors: Munteanu I., Florea N., 2009 and "Methodology for the Development of Pedological Studies ", ICPA, 1987. The classification of soils at type and subtype level was made according to" Romanian Soil Taxonomy System (SRTS) ", ICPA, 2012

PEDOLOGICAL STUDY OF LAND SUITABILITY IN THE AREA OF MAVRODIN TELEORMAN COUNTY, REGARDING THE ARRANGEMENT OF IRRIGATION WITH WATER FROM ZOOTECHNICAL COMPLEXES

The studied area is located in the center of Teleorman County, belonging to the Mavrodin cadastral territory, currently used as an arable land. The pedological mapping was performed with the purpose of identifying the soil area, assessing its fertility as well as the suitability for irrigation with wastewater. In this regard, a soil profile was opened and several surveys were collected from soil samples in natural and modified settlements, for morphological, physical and chemical analyzes. The soil type identified is red preluvosol. Geomorphologically, the land is part of the Roman Plain, the subunit of Burnaz, between the Danube Lunca, the Vedea, Teleorman and Calniştei valleys, extended west to the Teleorman river and the eastern limit of the county. The ground level is maintained between 8-10 m, with small fluctuations depending on the terrain. The type of soil identified, is classified in the luvisoluri class, having the following sequence of horizons: Ao-AB-Bt-C. The criteria for classification into classes, subclasses and other subunits of land according to the suitability to irrigate with waste water are those mentioned in chap. 10 from MESP, vol II (ICPA, 1987) with some additions. According to Annex 11.1 of the MESP, vol II (ICPA, 1987), the following additional criteria intervene in the selection of lands that can be irrigated with wastewater (soil type, soil texture, soil volume, soil thickness, erosion, soil unevenness, groundwater depth, excess surface moisture, other restrictions

Analysis of an atom laser based on the spatial control of the scattering length

In this paper we analyze atom lasers based on the spatial modulation of the scattering length of a Bose-Einstein Condensate. We demonstrate, through numerical simulations and approximate analytical methods, the controllable emission of matter-wave bursts and study the dependence of the process on the spatial dependence of the scattering length along the axis of emission. We also study the role of an additional modulation of the scattering length in time.Comment: Submitted to Phys. Rev.

Surface solitons in two-dimensional quadratic photonic lattices

We study two-color surface solitons in two-dimensional photonic lattices with quadratic nonlinear response. We demonstrate that such parametrically coupled optical localized modes can exist in the corners or at the edges of a square photonic lattice, and we analyze the impact of the phase mismatch on their properties, stability, and the threshold power for their generation.Comment: 3 double-column pages,5 figures, submited to Optics Letter

Stable three-dimensional spinning optical solitons supported by competing quadratic and cubic nonlinearities

We show that the quadratic interaction of fundamental and second harmonics in a bulk dispersive medium, combined with self-defocusing cubic nonlinearity, give rise to completely localized spatiotemporal solitons (vortex tori) with vorticity s=1. There is no threshold necessary for the existence of these solitons. They are found to be stable against small perturbations if their energy exceeds a certain critical value, so that the stability domain occupies about 10% of the existence region of the solitons. We also demonstrate that the s=1 solitons are stable against very strong perturbations initially added to them. However, on the contrary to spatial vortex solitons in the same model, the spatiotemporal solitons with s=2 are never stable.Comment: latex text, 10 ps and 2 jpg figures; Physical Review E, in pres

Stable spinning optical solitons in three dimensions

We introduce spatiotemporal spinning solitons (vortex tori) of the three-dimensional nonlinear Schrodinger equation with focusing cubic and defocusing quintic nonlinearities. The first ever found completely stable spatiotemporal vortex solitons are demonstrated. A general conclusion is that stable spinning solitons are possible as a result of competition between focusing and defocusing nonlinearities.Comment: 4 pages, 6 figures, accepted to Phys. Rev. Let

Vortex stability in nearly two-dimensional Bose-Einstein condensates with attraction

We perform accurate investigation of stability of localized vortices in an effectively two-dimensional ("pancake-shaped") trapped BEC with negative scattering length. The analysis combines computation of the stability eigenvalues and direct simulations. The states with vorticity S=1 are stable in a third of their existence region, $0<N<(1/3)N_{\max}^{(S=1)}$, where $N$ is the number of atoms, and $N_{\max}^{(S=1)}$ is the corresponding collapse threshold. Stable vortices easily self-trap from arbitrary initial configurations with embedded vorticity. In an adjacent interval, $(1/3)N_{\max }^{(S=1)}<N<$ $\allowbreak 0.43N_{\max}^{(S=1)}$, the unstable vortex periodically splits in two fragments and recombines. At $N>$ $\allowbreak 0.43N_{\max}^{(S=1)}$, the fragments do not recombine, as each one collapses by itself. The results are compared with those in the full 3D Gross-Pitaevskii equation. In a moderately anisotropic 3D configuration, with the aspect ratio $\sqrt{10}$, the stability interval of the S=1 vortices occupies $\approx 40$ of their existence region, hence the 2D limit provides for a reasonable approximation in this case. For the isotropic 3D configuration, the stability interval expands to 65% of the existence domain. Overall, the vorticity heightens the actual collapse threshold by a factor of up to 2. All vortices with $S\geq 2$ are unstable.Comment: 21 pages, 8 figures, to appear in Physical Review