Axion stabilization in modular cosmology

Abstract

The SL(2,ℤ) invariant α-attractor models proposed in [1] have plateau potentials with respect to the inflaton and axion fields. The potential in the axion direction is almost exactly flat during inflation, hence the axion field remains nearly massless. In this paper, we develop a generalized class of such models, where the SL(2,ℤ) symmetry is preserved, but the axion acquires a large mass and becomes strongly stabilized during inflation, which eliminates isocurvature perturbations in this scenario. Inflation in such two-field models occurs as in the single-field α-attractors and leads to the same cosmological predictions.