Kinetic Inflation in Stringy and Other Cosmologies

TL;DR

This paper investigates kinetic inflation driven by a dynamical Planck mass in string cosmology, highlighting challenges in achieving successful inflation and suggesting directions for improvement.

Contribution

It analyzes the limitations of simple kinetic inflation models in string cosmology and proposes potential directions for developing successful models.

Findings

Kinetic inflation alone cannot satisfy inflationary conditions in the Einstein frame.

In the Jordan frame, graceful exit and flatness problems are identified.

Simple formulations of kinetic inflation are insufficient for successful inflation.

Abstract

An inflationary epoch driven by the kinetic energy density in a dynamical Planck mass is studied. In the conformally related Einstein frame it is easiest to see the demands of successful inflation cannot be satisfied by kinetic inflation alone. Viewed in the original Jordan-Brans-Dicke frame, the obstacle is manifest as a kind of graceful exit problem and/or a kind of flatness problem. These arguments indicate the weakness of only the simplest formulation. {}From them can be gleaned directions toward successful kinetic inflation.