Speaker: Ashoke Sen Title: Wall Crossing from Boltzmann Black Hole Halos Abstract: By representing the potentially unstable bound states as multi-centered black hole solutions in N=2 supergravity, we provide explicit formula for the change in the (refined) index across a wall of marginal stability. The main physical insight behind our results is that the Bose-Fermi statistics of individual black holes participating in the bound state can be traded for Maxwell-Boltzmann statistics, provided the integer valued index is replaced by an effective rational valued index.