Dynamics of localized structures in vector waves

Dynamical properties of topological defects in a twodimensional complex vector field are considered. These objects naturally arise in the study of polarized transverse light waves. Dynamics is modeled by a Vector Complex Ginzburg-Landau Equation with parameter values appropriate for linearly polarized laser emission. Creation and annihilation processes, and selforganization of defects in lattice structures, are described. We find "glassy" configurations dominated by vectorial defects and a melting process associated to topological-charge unbinding.Comment: 4 pages, 5 figures included in the text. To appear in Phys. Rev. Lett. (2000). Related material at http://www.imedea.uib.es/Nonlinear and http://www.imedea.uib.es/Photonics . In this new version, Fig. 3 has been replaced by a better on

Migration, Ethnicity and Economic Integration

This chapter deals with the economic and ethnic diversity caused by international labor migration, and their economic integration possibilities. It brings together three strands of literature dealing with the neoclassical economic assimilation, ethnic identities and attitudes towards immigrants and the natives, and provides an analysis in understanding their interactions. The issue of how immigrants fare in the host country especially in terms of their labor force participation and remuneration has been the core of research in the labor migration literature. If immigrants fare as well as the natives, then they are economically assimilated. While some immigrant groups do, most do not, especially in Europe. Of equal importance is how immigrants identify with the culture of their home and receiving countries, and if natives and immigrants have the right attitudes about each other. Ethnic identities and attitudes seem to be less affected by the economic environment but have implications for economic performance