The Effective Field Theory of nonsingular cosmology
  In this paper, we explore the nonsingular cosmology within the framework of
the Effective Field Theory(EFT) of cosmological perturbations. Due to the
recently proved no-go theorem, any nonsingular cosmological models based on the
cubic Galileon suffer from pathologies. We show how the EFT could help us
clarify the origin of the no-go theorem, and offer us solutions to break the
no-go. Particularly, we point out that the gradient instability can be removed
by using some spatial derivative operators in EFT. Based on the EFT
description, we obtain a realistic healthy nonsingular cosmological model, and
show the perturbation spectrum can be consistent with the observations.
