Cosmological constraints on primordial black holes produced in the   near-critical gravitational collapse
  The mass function of primordial black holes created through the near-critical gravitational collapse is calculated in a manner fairly independent of the statistical distribution of underlying density fluctuation, assuming that it has a sharp peak on a specific scale. Comparing it with various cosmological constraints on their mass spectrum, some newly excluded range is found in the volume fraction of the region collapsing into black holes as a function of the horizon mass. 
Jun'ichi Yokoyama (Stanford U. and Yukawa Institute, Kyoto U.)