On the strong coupling problem in cosmologies with “strong gravity in the past”

Abstract

In this paper, we examine the potential strong coupling problem at early times in a bouncing cosmological model with “strong gravity in the past” (Jordan frame), which is conformally related to inflation (Einstein frame). From naive-dimensional analysis in the Jordan frame, one would conclude that the quantum strong coupling energy scale can be lower than the classical energy scale. However, from the Einstein frame prospective, this should not be the case. We illustrate this point by calculation in the Jordan frame which shows cancellations of the dangerous contributions in the tree level amplitude.