Monodromy Inflation in SUSY QCD

TL;DR

The paper addresses how to realize large-field inflation via monodromy in a controllable 4D field theory by embedding monodromy in SUSY QCD with a large number of colors and coupling to supergravity. It shows that anomaly-mediated dynamics yield a natural-inflation–type potential with an effective decay constant $f = N\phi$ and a scale $\Lambda^4 \sim 6 W_{np} m_{3/2}$, permitting transplanckian field excursions for the angular mode while stabilizing the radial direction with soft SUSY breaking. Achieving the observationally favored spectral index and tensor-to-scalar ratio requires $f \gtrsim 10 M_{pl}$ and careful hierarchies among scales, though percent-level tunings and potential tunneling constraints arise. As a tractable field-theoretic realization of monodromy inflation, the model provides a playground to study quantum gravity corrections, EFT consistency, and tunneling effects in large-field inflation.

Abstract

The discovery of a large tensor-to-scalar ratio by the BICEP2 experiment points to large field excursions during inflation. One framework that predicts large $r$ is monodromy inflation. While discussed mainly in the context of string theory, the phenomenon can be illustrated and studied in the well-understood framework of SUSY QCD with a large number of colors. We discuss the requirements for viable inflation as well as various difficulties for model building, including tunneling, tuning, and the species problem.

Figures (1)

• Figure 1: Schematic plot of the potential for the phases of the gaugino bilinear and the $\bar{Q}Q$ modulus in $N=4,~N_f=1$ SQCD. The dashed line is the domain of the effective theory at low energies, and it passes through multiple vacua (blue). For fixed $\bar{Q}Q$, there are $N-1=3$ branches of gaugino vacua.