Gauge field theory approach to spin transport in a 2D electron gas

We discuss the Pauli Hamiltonian including the spin-orbit interaction within an U(1) x SU(2) gauge theory interpretation, where the gauge symmetry appears to be broken. This interpretation offers new insight into the problem of spin currents in the condensed matter environment, and can be extended to Rashba and Dresselhaus spin-orbit interactions. We present a few outcomes of the present formulation: i) it automatically leads to zero spin conductivity, in contrast to predictions of Gauge symmetric treatments, ii) a topological quantization condition leading to voltage quantization follows, and iii) spin interferometers can be conceived in which, starting from a arbitrary incoming unpolarized spinor, it is always possible to construct a perfect spin filtering condition.Comment: Invited contribution to Statphys conference, June 2009, Lviv (Ukraine

Informal Economy: Is It a Problem, a Solution or Both? The Perspective of the Informal Business

This paper deals with the informal economy. For many it is a solution, for others it is a problem. What can the law do to incorporate the informal economy into the formal economy? Does it really matter? What are the challenges

Preparing for CAFTA-DR: The Need of Commercial Law Reform in Central America

This article explores the policies, laws and institutions that may prevent Central American States from exploiting the opportunities provided by the CAFTA-DR. In that sense, we examine several of the legal factors that appear to be important in determining economic growth as they apply to the commercial legal conditions of Costa Rica, El Salvador, Guatemala, Honduras and Nicaragua

La competitividad empresarial desde el contexto de las negociaciones Forward en una empresa del sector arrocero : caso comercializadora la Espiga E.U

Uno de los objetivos fundamentales de toda compañía es cumplir a satisfacción con cada una de las exigencias que genera el cliente y que estén al alcance y dentro del contexto estratégico y operacional de la empresa; es por ello que éstas hacen todo lo necesario para poder alcanzar dicho nivel, y crear por ende, un lazo entre la empresa y el cliente, donde este último exponga sus deseos y/o necesidades para una pronta solución por parte de la empresa. Las compañías hoy en día entre más competitivas se muestren, mejores oportunidades de permanecer en el mercado tendrán, ya que buscarán siempre la excelencia en cada etapa de su cadena de valor, para así volverse más efectivas y como resultado, permanecer en el duro entorno y mercado en el que se desempeñan; es por ello que siempre será necesario revisar y evaluar la organización constantemente, para encontrar los puntos débiles que de cierta forma podría poner en riesgo a la empresa y sacarla de su mercado. El siguiente proyecto muestra una herramienta utilizada por una empresa como mecanismo de ingreso a un nuevo mercado, donde le sirvió como ayuda para el abastecimiento seguro de su materia prima; el objetivo es evaluar que tan competente fue la empresa al momento de poner en práctica dicha herramienta y qué mejoras podrá implementar en el esquema interno de la misma, proponiendo algunas estrategias que ayudarán a subir su nivel competitivo en el ámbito funcional, de negocios y corporativo

Wigner phase space distribution as a wave function

We demonstrate that the Wigner function of a pure quantum state is a wave function in a specially tuned Dirac bra-ket formalism and argue that the Wigner function is in fact a probability amplitude for the quantum particle to be at a certain point of the classical phase space. Additionally, we establish that in the classical limit, the Wigner function transforms into a classical Koopman-von Neumann wave function rather than into a classical probability distribution. Since probability amplitude need not be positive, our findings provide an alternative outlook on the Wigner function's negativity.Comment: 6 pages and 2 figure

Time-resolved broadband analysis of slow-light propagation and superluminal transmission of electromagnetic waves in three-dimensional photonic crystals

A time-resolved analysis of the amplitude and phase of THz pulses propagating through three-dimensional photonic crystals is presented. Single-cycle pulses of THz radiation allow measurements over a wide frequency range, spanning more than an octave below, at and above the bandgap of strongly dispersive photonic crystals. Transmission data provide evidence for slow group velocities at the photonic band edges and for superluminal transmission at frequencies in the gap. Our experimental results are in good agreement with finite-difference-time-domain simulations.Comment: 7 pages, 11 figure