On Viability of Inflation in Nonminimal Kinetic Coupling Theory

Abstract

Abstract: We consider the initial conditions for inflation in the nonminimal kinetic coupling theory. If inflation is driven solely by the kinetic term with no potential, the resulting number of e-folds depends only on the initial velocity of the scalar field, φ. We write down the expression for the number of e-folds explicitly, and show that for physically reasonable values of the coupling constant, we can get 60 e-folds only for an exponentially big initial φ. When the scalar field potential is taken into account, a double inflation scenario arises, where the first inflation is kinetic term driven, while the second one is potential term driven. In this case, we need not a very large φ to start with for 60 e-folds, on the other hand, some initial conditions lead to a physically inadmissible eternal inflation. We show numerically that in the measure used in the present paper only a smaller part of initial conditions leads to eternal inflation for reasonable values of the coupling constant.