Conservation laws in Skyrme-type models

The zero curvature representation of Zakharov and Shabat has been generalized recently to higher dimensions and has been used to construct non-linear field theories which either are integrable or contain integrable submodels. The Skyrme model, for instance, contains an integrable subsector with infinitely many conserved currents, and the simplest Skyrmion with baryon number one belongs to this subsector. Here we use a related method, based on the geometry of target space, to construct a whole class of theories which are either integrable or contain integrable subsectors (where integrability means the existence of infinitely many conservation laws). These models have three-dimensional target space, like the Skyrme model, and their infinitely many conserved currents turn out to be Noether currents of the volume-preserving diffeomorphisms on target space. Specifically for the Skyrme model, we find both a weak and a strong integrability condition, where the conserved currents form a subset of the algebra of volume-preserving diffeomorphisms in both cases, but this subset is a subalgebra only for the weak integrable submodel.Comment: Latex file, 22 pages. Two (insignificant) errors in Eqs. 104-106 correcte

Significado léxico y significado textual de la unidad lexemática "dar"

Este artículo presenta un estudio de la unidad verbal “dar” desde una perspectiva lexemático-sintáctica, ya que ésta permite observar las correferencias entre los rasgos léxico-semánticos y sintácticos. En este análisis hemos comprobado que la producción idealizada no siempre coincide con el comportamiento actualizado del habla de Sevilla y de los textos periodísticos. La mayoría de las veces, el significado del verbo depende del entorno sintáctico y del valor semántico de los significados con los que se construye. This article shows an analysis of the verbal-unit “dar” from a lexematic-syntactic perspective, because it allows to observe the correference between the characteristics semantics and the syntactics ones. In this analysis we have verified that the idealizaed production does not always coincide with the actual behaviour of Seville speech and of the journalistic texts. Most of times, the meaning of the verb depends on syntactic environment and semantic value of the nominal group that is built with