Initial conditions for inflation and the energy scale of SUSY-breaking from the (nearly) gaussian sky

TL;DR

The paper explores how initial conditions for small-field inflation can naturally arise in multi-field models with non-linear angular friction, and relates the SUSY-breaking scale to observable non-Gaussian fluctuations, constraining it to around 10^{13} GeV.

Contribution

It introduces a mechanism for natural initial conditions in small-field inflation via non-linear angular friction and links SUSY-breaking scale to non-Gaussianity, providing tight observational constraints.

Findings

Non-linear angular friction enables inflation from arbitrary initial conditions.

A relation between SUSY-breaking scale and non-Gaussianity is established.

Current Planck data constrains SUSY-breaking scale to 3-7 x 10^{13} GeV.

Abstract

We show how general initial conditions for small field inflation can be obtained in multi-field models. This is provided by non-linear angular friction terms in the inflaton that provide a phase of non-slow-roll inflation before the slow-roll inflation phase. This in turn provides a natural mechanism to star small-field slow-roll at nearly zero velocity for arbitrary initial conditions. We also show that there is a relation between the scale of SUSY breaking sqrt (f) and the amount of non-gaussian fluctuations generated by the inflaton. In particular, we show that in the local non-gaussian shape there exists the relation sqrt (f) = 10^{13} GeV sqrt (f_NL). With current observational limits from Planck, and adopting the minimum amount of non-gaussian fluctuations allowed by single-field inflation, this provides a very tight constraint for the SUSY breaking energy scale sqrt (f) = 3-7 x 10^{13} GeV at 95% confidence. Further limits, or detection, from next year's Planck polarisation data will further tighten this constraint by a factor of two. We highlight that the key to our approach is to identify the inflaton with the scalar component of the goldstino superfield. This superfield is universal and implements the dynamics of SUSY breaking as well as superconformal breaking.