The Lightest of Black Holes
  In this paper we consider general relativity in the large $N$ limit, where $N$ stands for the number of particles in the model. Studying the resummed graviton propagator, we propose to interpret its complex poles as black hole precursors. Our main result is the calculation of the mass and width of the lightest of black holes. We show that the values of the masses of black hole precursors depend on the number of fields in the theory. Their masses can be lowered down to the TeV region by increasing the number of fields in a hidden sector that only interacts gravitationally with the standard model. 
Xavier Calmet
hep-th gr-qc