Self-organized evolution in socio-economic environments

We propose a general scenario to analyze social and economic changes in modern environments. We illustrate the ideas with a model that incorporating the main trends is simple enough to extract analytical results and, at the same time, sufficiently complex to display a rich dynamic behavior. Our study shows that there exists a macroscopic observable that is maximized in a regime where the system is critical, in the sense that the distribution of events follow power-laws. Computer simulations show that, in addition, the system always self-organizes to achieve the optimal performance in the stationary state.Comment: 4 pages RevTeX; needs epsf.sty and rotate.sty; submitted to Phys Rev Let

Theoretical studies of Si and GaAs surfaces and initial steps in the oxidation

Using ab initio quantum chemical methods (generalized valence bond), we examine (i) the electronic states of Si (111) and GaAs (110) surface, (ii) the relaxation of the Si (111) surface, (iii) the reconstruction of the GaAs surface, (iv) the initial steps in the chemisorption of O_2 on Si (111), and (v) the bonding of O atom to Ga and As centers