Bounce beyond Horndeski with GR asymptotics and $\gamma$-crossing

Abstract

It is known that beyond Horndeski theory admits healthy bouncing cosmological solutions. However, the constructions proposed so far do not reduce to General Relativity (GR) in either infinite past or infinite future or both. The obstacle is so called $\gamma$-crossing, which off hand appears pathological. By working in the unitary gauge, we confirm the recent observation by Ijjas [arXiv:1710.05990] that $\gamma$-crossing is, in fact, healthy. On this basis we construct a spatially flat, stable bouncing Universe solution whose asymptotic past and future are described by GR with conventional massless scalar field.