Nonsingular bouncing cosmologies in light of BICEP2
  We confront various nonsingular bouncing cosmologies with the recently released BICEP2 data and investigate the observational constraints on their parameter space. In particular, within the context of the effective field approach, we analyze the constraints on the matter bounce curvaton scenario with a light scalar field, and the new matter bounce cosmology model in which the universe successively experiences a period of matter contraction and an ekpyrotic phase. Additionally, we consider three nonsingular bouncing cosmologies obtained in the framework of modified gravity theories, namely the Ho\v{r}ava-Lifshitz bounce model, the $f(T)$ bounce model, and loop quantum cosmology. 
Yi-Fu Cai, Jerome Quintin, Emmanuel N. Saridakis, Edward Wilson-Ewing
astro-ph.CO gr-qc hep-th