Landscape, the Scale of SUSY Breaking, and Inflation

TL;DR

The paper investigates constraints on the inflation scale in KKLT models of string cosmology, showing that simple models limit the Hubble constant to the gravitino mass, but more complex racetrack models can circumvent this restriction.

Contribution

It demonstrates that the standard KKLT model constrains the inflation scale by the gravitino mass, while racetrack superpotential models can allow high-scale inflation with low gravitino mass.

Findings

Simple KKLT models limit Hubble to gravitino mass

Racetrack models can achieve high-scale inflation with low gravitino mass

Implications for SUSY breaking scale and inflation model building

Abstract

We argue that in the simplest version of the KKLT model, the maximal value of the Hubble constant during inflation cannot exceed the present value of the gravitino mass, H< m_{3/2}. This may have important implications for string cosmology and for the scale of the SUSY breaking in this model. If one wants to have inflation on high energy scale, one must develop phenomenological models with an extremely large gravitino mass. On the other hand, if one insists that the gravitino mass should be O(1 TeV), one will need to develop models with a very low scale of inflation. We show, however, that one can avoid these restrictions in a more general class of KKLT models based on the racetrack superpotential with more than one exponent. In this case one can combine a small gravitino mass and low scale of SUSY breaking with the high energy scale of inflation.