Bose-Einstein condensation in quasi-2D systems: applications to high Tc superconductivity

We describe high-Tc superconductivity in layered materials within a BCS theory as a BEC of massless-like Cooper pairons satisfying a linear dispersion relation, and propagating within quasi-2D layers of finite width defined by the charge distribution about the CuO_2 planes. We obtain a closed formula for the critical temperature, Tc, that depends on the layer width, the binding energy of Cooper's pairs, and the average in-plane penetration depth. This formula reasonably reproduces empirical values of superconducting transition temperatures for several different cuprate materials near the optimal doping regime, as well as for YBCO films with different doping degrees.Comment: 5 pages, 1 figur

Algebraic methods for parameterized codes and invariants of vanishing ideals over finite fields

Let K be a finite field with q elements and let X be a subset of a projective space P^{s-1}, over the field K, which is parameterized by Laurent monomials. Let I(X) be the vanishing ideal of X. Some of the main contributions of this paper are in determining the structure of I(X) and some of their invariants. It is shown that I(X) is a lattice ideal. We introduce the notion of a parameterized code arising from X and present algebraic methods to compute and study its dimension, length and minimum distance. For a parameterized code arising from a connected graph we are able to compute its length and to make our results more precise. If the graph is non-bipartite, we show an upper bound for the minimum distance. We also study the underlying geometric structure of X.Comment: Finite Fields Appl., to appea

Las teorías de la localización de la inversión extranjera directa (IED): una aproximación (Localization theories of the foreign direct investment: an approach)

El objetivo de esta obra es presentar una aproximación al estado actual del arte en el tema. En este sentido, se intentarán exponer los motivos que desencadenan que las diversas teorías relativas a la Inversión Extranjera Directa (IED) no proporcionen una respuesta unánime sobre la localización del capital extranjero con fines productivos, enfatizando la ausencia de modelos cuantitativos para explicar los factores en la decisión de invertir en el extranjero. Se presentan los conceptos y definiciones fundamentales relacionados con el tema. Finalmente, ofrece una perspectiva sobre el quehacer en las investigaciones relacionadas al tema. The objective of this work is to present an approximation of the state of the art in the theme. For this purpose, I will try to illustrate the motives in order to unravel why the diverse theories of the Foreign Direct Investment (FDI) do not provide a unanimous response to the role of the foreign capital on productive end, emphasizing the absence of quantitative models to explain the factors that are essential in decision making of investing abroad. The concepts are presented and fundamental definitions related to the theme are pointed out. Finally, I offer a new perspective as how to conduct reasearch on this subject