Nonlinear wave dynamics in honeycomb lattices

We study the nonlinear dynamics of wave packets in honeycomb lattices, and show that, in quasi-1D configurations, the waves propagating in the lattice can be separated into left-moving and right-moving waves, and any wave packet composed of left (or right) movers only does not change its intensity structure in spite of the nonlinear evolution of its phase. We show that the propagation of a general wave packet can be described, within a good approximation, as a superposition of left and right moving self-similar (nonlinear) solutions. Finally, we find that Klein tunneling is not suppressed due to nonlinearity

The (ir)Relevance of Initial Conditions in Soft Leptogenesis

We explore how the initial conditions affect the final lepton asymmetry in Soft Leptogenesis. It has been usually assumed that the initial state is a statistical mixture of sterile sneutrinos and anti-sneutrinos with equal abundances. We calculate the lepton asymmetry due to the most general initial mixture. The usually assumed equal mixture produces a small, but sufficient, lepton asymmetry which is proportional to the ratio of the supersymmetry breaking scale over the Majorana scale. A more generic mixture, still with equal contents of sneutrinos and anti sneutrinos, yields an unsuppressed lepton asymmetry. Mixtures of non equal contents of sneutrinos and anti sneutrinos result in a large lepton asymmetry too. While these results establish the robustness of Soft Leptogenesis and other mixing based mechanisms, they also expose their lack of predictive power.Comment: v1: 12 pages; v2: typos corrected; v3: published version with new discussions and reference

Breakdown of Dirac Dynamics in Honeycomb Lattices due to Nonlinear Interactions

We study the dynamics of coherent waves in nonlinear honeycomb lattices and show that nonlinearity breaks down the Dirac dynamics. As an example, we demonstrate that even a weak nonlinearity has major qualitative effects one of the hallmarks of honeycomb lattices: conical diffraction. Under linear conditions, a circular input wave-packet associated with the Dirac point evolves into a ring, but even a weak nonlinearity alters the evolution such that the emerging beam possesses triangular symmetry, and populates Bloch modes outside of the Dirac cone region. Our results are presented in the context of optics, but we propose a scheme to observe equivalent phenomena in Bose-Einstein condensates

Disseny de protecció catòdica d'estructures offshore/màster

Based on the standpoint of the environment, corrosion is an environmental occurrence that is required to maintain the natural balance. From the engineer’s standpoint, this natural balance is observed as a damaging natural attack on a metal by an electrochemical reaction. This natural attack has various types such as uniform, crevice or pitting corrosion and it results in severe material loss, which contributes to lost production and increased maintenance, repair, and replacement costs, as well as restoration costs. Hence, prevention of corrosion is quite significant for metal to be applied in an offshore platform

Jewish - Relaciones sociales de estudiantes árabes en Israel

In Israel Jews and Arabs view each other as enemies. This study examined attitudes of Jewish and Arab students, who are studying in the same academic space, towards each other. Three categories were examined: Stereotypes (cognitive component); emotions (affective component); willingness to be in social contact (behavioral component). Questionnaires were distributed to 170 nursing students  Arabs and Jews. Results showed that third and fourth-year students revealed more positive emotions, positive stereotypes and willingness to be in social contact that first-year student.En Israel, los judíos y los árabes se ven como enemigos entre ellos. Este estudio examinó las actitudes entre ellos de los estudiantes judíos y árabes, que estudian en el mismo espacio académico. Se examinaron tres categorías: estereotipos (componente cognitivo); emociones (componente afectivo); ganas de estar en contacto social (componente de comportamiento). Se distribuyeron cuestionarios a 170 estudiantes de enfermería, árabes y judíos. Los resultados mostraron que los estudiantes de tercer y cuarto año revelaron más emociones positivas, estereotipos positivos y voluntad de estar en contacto social que los estudiantes de primer año