Sigma Model Corrections to the Confining Background

Sigma model ($\alpha^{\prime}$) corrections to the confining string background are obtained. The main result is that the Poincar\'e invariant ansatz is maintained. Physical conditions for the dissapearance of the naked singularity are discussed.Comment: LaTeX,12 page

Generators of D-modules in positive characteristic

Let R be either a polynomial or a formal power series ring in a finite number of variables over a field k of characteristic p > 0 and let D be the ring of klinear differential operators of R. In this paper we prove that if f is a non-zero element of R then R[1/f], obtained from R by inverting f, is generated as a D-module by 1/f . This is very much in contrast to the characteristic zero situation where the corresponding statement is false (there the generation is governed by the roots of the Bernstein polynomial of f). In fact we prove analogs of the above result for a considerably wider class of rings R and a considerably wider class of D-modules.Comment: 15 pages. combines and extends the results of math.AC/0407464 and math.AC/0408124. to appear in Mathematical Research Letter

Tartesos : mito y realidad

Esta civilización ha obsesionado a eruditos y aficionados a la historia. Sin duda, un enigma historiográfico tras el que podría hallarse el reflejo de la colonización fenicia en el sur peninsular y en consecuenia, como señalan algunas fuentes, de la antigua ciudad de Gadir o de la propia Huelv

Determination of the strong coupling αs from transverse energy-energy correlations in multi-jet events at √ s = 13 TeV with the ATLAS detector

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Teórica. Fecha de Lectura: 24-02-202

Overdamped Deterministic Ratchets Driven By Multifrequency Forces

We investigate a dissipative, deterministic ratchet model in the overdamped regime driven by a {\it rectangular force}. Extensive numerical calculations are presented in a diagram depicting the drift velocity as a function of a wide range of the driving parameter values. We also present some theoretical considerations which explain some features of the mentioned diagram. In particular, we proof the existence of regions in the driving parameter space with bounded particle motion possessing zero current. Moreover, we present an explicit analytical expression for the drift velocity in the adiabatic limit.Comment: 12 pages, 6 figure