Dynamic Aspects of Teenage Friendships and Educational Attainment

We study peer effects in education. We first develop a network model that predicts a relationship between own education and peers’ education as measured by direct links in the social network. We then test this relationship using the four waves of the AddHealth data, looking at the impact of school friends nominated in the first wave in 1994-1995 on own educational outcome reported in the fourth wave in 2007-2008. We find that there are strong and persistent peer effects in education since a standard deviation increase in peers’ education attainment translates into roughly a 10 percent increase of a standard deviation in the individual’s education attainment (roughly 3.5 more months of education). We also find that peer effects are in fact significant only for adolescents who were friends in grades 10-12 but not for those who were friends in grades 7-9. This might indicate that social norms are important in educational choice since the individual’s choice of college seems to be influenced by that of friends in the two last years of high school.Social networks; education; peer effects; identification strategy

Following the evolution of glassy states under external perturbations: compression and shear-strain

We consider the adiabatic evolution of glassy states under external perturbations. Although the formalism we use is very general, we focus here on infinite-dimensional hard spheres where an exact analysis is possible. We consider perturbations of the boundary, i.e. compression or (volume preserving) shear-strain, and we compute the response of glassy states to such perturbations: pressure and shear-stress. We find that both quantities overshoot before the glass state becomes unstable at a spinodal point where it melts into a liquid (or yields). We also estimate the yield stress of the glass. Finally, we study the stability of the glass basins towards breaking into sub-basins, corresponding to a Gardner transition. We find that close to the dynamical transition, glasses undergo a Gardner transition after an infinitesimal perturbation.Comment: 4 pages (3 figures) + 24 pages (5 pages) of appendice