Tracing Primordial Black Holes in Nonsingular Bouncing Cosmology
  We in this paper investigate the formation and evolution of primordial black holes (PBHs) in nonsingular bouncing cosmologies. We discuss the formation of PBH in the contracting phase and calculate the PBH abundance as a function of the sound speed and Hubble parameter. Afterwards, by taking into account the subsequent PBH evolution during the bouncing phase, we derive the density of PBHs and their Hawking radiation. Our analysis shows that nonsingular bounce models can be constrained from the backreaction of PBHs. 
Jie-Wen Chen, Junyu Liu, Hao-Lan Xu, Yi-Fu Cai
gr-qc astro-ph.CO hep-th