Accidentally light scalars from large representations

TL;DR

This paper explores models with large scalar representations where certain scalars become unexpectedly light due to loop effects, with potential applications in cosmology and particle physics.

Contribution

It introduces minimal models with large group representations exhibiting accidentally light scalars, highlighting their origin and potential implications.

Findings

Scalar masses can be loop-suppressed compared to naive expectations.

Minimal models with SU(2) five-plet and SU(3) ten-plet are constructed.

Flat directions are lifted by radiative corrections, leading to light scalars.

Abstract

In models with spontaneous symmetry breaking by scalar fields in large group representations, we observe that some of the scalar masses can be loop-suppressed with respect to the naive expectation from symmetry selection rules. We present minimal models -- the $\rm{SU(2)}$ five-plet and $\rm{SU(3)}$ ten-plet -- with such accidentally light scalars, featuring compact tree-level flat directions lifted by radiative corrections. We sketch some potential applications, from stable relics and slow roll in cosmology, to hierarchy and fine-tuning problems in particle physics.