Perturbative Approach to Symmetric Mass Generation

The Landau paradigm has been a powerful framework for understanding phase transitions involving spontaneous symmetry breaking. In contrast, phase transitions between two symmetric phases, where neither phase breaks any symmetry, remain less explored. One intriguing class of such transitions involves "symmetric mass generation" (SMG), where interactions drive a transition from a gapless symmetric phase to a gapped symmetric phase. In this Letter, we develop a controlled perturbative approach to study a class of such transitions, based on an ε expansion around the critical dimension where the SMG-inducing interaction becomes marginal. Applying this method to two distinct models, we identify a single-parameter-tuned transition in each case, which we conjecture captures the universal critical behavior of the SMG transition in these models. We compute universal quantities associated with these transitions.