Bounce in GR and higher-order derivative operators
  Recent progress seems to suggest that one must modify General Relativity (GR)
to stably violate the null energy condition and avoid the cosmological
singularity. However, with the higher-order derivative operators of scalar
field (a subclass of the degenerate higher-order scalar-tensor theory), we show
that at energies well below the Planck scale, fully stable nonsingular
cosmologies can actually be implemented within GR.
