Bloch oscillations in optical and Zeeman lattices in the presence of spin-orbit coupling

We address Bloch oscillations of a spin-orbit coupled atom in periodic potentials of two types: optical and Zeeman lattices. We show that in optical lattices the spin-orbit coupling allows controlling the direction of atomic motion and may lead to complete suppression of the oscillations at specific values of the coupling strength. In Zeeman lattices the energy bands are found to cross each other at the boundaries of the Brillouin zone, resulting in period doubling of the oscillations. In all cases, the oscillations are accompanied by rotation of the pseudospin, with a dynamics that is determined by the strength of the spin-orbit coupling. The predicted effects are discussed also in terms of a Wannier-Stark ladder, which in optical lattices consist of two mutually shifted equidistant subladders.Peer ReviewedPostprint (author's final draft

Rotating vortex clusters in media with inhomogeneous defocusing nonlinearity

We show that media with inhomogeneous defocusing cubic nonlinearity growing toward the periphery can support a variety of stable vortex clusters nested in a common localized envelope. Nonrotating symmetric clusters are built from an even number of vortices with opposite topological charges, located at equal distances from the origin. Rotation makes the clusters strongly asymmetric, as the centrifugal force shifts some vortices to the periphery, while others approach the origin, depending on the topological charge. We obtain such asymmetric clusters as stationary states in the rotating coordinate frame, identify their existence domains, and show that the rotation may stabilize some of them.Peer ReviewedPostprint (author's final draft

On Spin-driven inflation from fields in General Relativity and COBE data

Obukhov spin-driven inflation in General Relativity is extended to include inflaton fields.A de Sitter phase solution is obtained and new slow-rolling conditions for the spin potential are obtained.The spin potential reduces to Obukhov result at the present epoch of the Universe where the spin density is low with comparison to the Early Universe spin densities.A relation betwenn the spin density energy and the temperature fluctuation can be obtained which allow us to determine the spin density energy in terms of the COBE data for temperature fluctuations.Comment: Latex file 8K

Multiple-Notch Frequency Selective Surface for Automotive Applications

A one-layer frequency selective surface (FSS) is proposed for wide-band and multiple-notch filtering applications. The structure consists of one or two pairs of modified square rings on one side of the supporting dielectric layer. Two, three and four notches are obtained by modifying the parameters involved. A parametric analysis concerning the frequency response in function of the substrate thickness is reported, demonstrating the possibility of changing the stop bands and providing design flexibility. By duplicating the structure on both sides of the FR4 substrate, a wide band is obtained, for both TE and TM polarizations. The devised FSS can be used for filtering in the Wi-Fi, Bluetooth and X bands for Automotive applications. The analysis is realized by full-wave electromagnetic simulation

Metastability of quantum droplet clusters

We show that metastable ring-shaped clusters can be constructed from two-dimensional quantum droplets in systems described by the Gross-Pitaevskii equations augmented with Lee-Huang-Yang quantum corrections. The clusters exhibit dynamical behaviours ranging from contraction to rotation with simultaneous periodic pulsations, or expansion, depending on the initial radius of the necklace pattern and phase shift between adjacent quantum droplets. We show that, using an energy-minimization analysis, one can predict equilibrium values of the cluster radius that correspond to rotation without radial pulsations. In such a regime, the clusters evolve as metastable states, withstanding abrupt variations in the underlying scattering lengths and keeping their azimuthal symmetry in the course of evolution, even in the presence of considerable perturbations.Peer ReviewedPostprint (author's final draft

Frequency Selective Surface with Two Quasi-Independent Notch Frequencies

A double-layer frequency selective surface (FSS) built on FR4 substrate exhibiting two notch frequencies in the 0–10-GHz range is introduced. Recently published examples demonstrate that further research needs to be undergone for obtaining separate tuning of the resulted notch frequencies. Thus, this issue is addressed in this paper: the notch frequencies can be quasi-independently set by appropriate values given to the geometrical parameters of the two metal patterns in the unit cells of the structure. The FSS behavior is stable with respect to the angle of incidence of impinging electromagnetic waves up to 45°, as proved by simulation and validated by experiments

Empleo de isótopos ambientales para discernir la contaminación salina de la cuenca del río Llobregat

La formación geológica salina de la comarca del Bages(Barcelona) y su explotación minera en diferentes puntos de la cuenca del Llobregat, influyen en la salinización de los ríos Cardener y Llobregat. La cuenca potásica catalana presenta dos peculiaridades: la formación salina tiene un afloramiento en Cardona, y en algunas zonas las capas de mineral se encuentran cerca de la superficie pero sin aflorar. La geología del terreno puede influir en la salinidad de las aguas de la cuenca por contacto directo con los materiales salinos. La actividad minera de Cardona (cerrada en 1990), Suria,Balsareny y Sallent, genera en la producción del mineral un residuo salino que se acumula en el exterior de las minas formándose las escombreras salinas o «runams». Sus salessolubles se disuelven con la lluvia, y pueden llegar a las aguas superficiales y aguas subterráneas del entorno. El objetivo de este trabajo es evaluar las aportaciones salinas a la cuenca del río Llobregat, separando las de origen natural y las de procedencia antrópica, utilizando la composición isotópica del azufre y del oxigeno del sulfato disuelto en sus aguas. También se cuantifica el origen natural y antrópico de los cloruros que se aportan

Three-dimensional droplets of swirling superfluids

A new method for the creation of 3D solitary topological modes, corresponding to vortical droplets of a two-component dilute superfluid, is presented. We use the recently introduced system of nonlinearly coupled Gross-Pitaevskii equations, which include contact attraction between the components, and quartic repulsion stemming from the Lee-Huang-Yang correction to the mean-field energy. Self-trapped vortex tori, carrying the topological charges m1=m2=1 or m1=m2=2 in their components, are constructed by means of numerical and approximate analytical methods. The analysis reveals stability regions for the vortex droplets (in broad and relatively narrow parameter regions for m1=m2=1 and m1=m2=2, respectively). The results provide the first example of stable 3D self-trapped states with the double vorticity, in any physical setting. The stable modes are shaped as flat-top ones, with the space between the inner hole, induced by the vorticity, and the outer boundary filled by a nearly constant density. On the other hand, all modes with hidden vorticity, i.e., topological charges of the two components m1=-m2=1, are unstable. The stability of the droplets with m1=m2=1 against splitting (which is the main scenario of possible instability) is explained by estimating analytically the energy of the split and un-split states. The predicted results may be implemented, exploiting dilute quantum droplets in mixtures of Bose-Einstein condensates.Peer ReviewedPostprint (author's final draft