Symmetric Mass Generation with four SU(2) doublet fermions

TL;DR

This paper investigates a lattice SU(2) gauge theory with four fermions, revealing a new symmetric mass generation phase at strong coupling and evidence of a continuous phase transition, suggesting a potential continuum limit.

Contribution

It introduces a novel symmetric mass generation phase in SU(2) gauge theory with four fermions and provides evidence for a continuous phase transition at this boundary.

Findings

Identification of a confining SMG phase at strong coupling

Evidence for a continuous phase transition between phases

RG flow analysis indicating a quadratic vanishing beta function

Abstract

We study a single exactly massless staggered fermion in the fundamental representation of an $SU(2)$ gauge group. We utilize an nHYP-smeared fermion action supplemented with additional heavy Pauli-Villars fields which serve to decrease lattice artifacts. The phase diagram exhibits a clear two-phase structure with a conformal phase at weak coupling and a novel new phase, the Symmetric Mass Generation (SMG) phase, appearing at strong coupling. The SMG phase is confining with all states gapped and chiral symmetry unbroken. Our finite size scaling analysis provides strong evidence that the phase transition between these two phases is continuous, which would allow for the existence of a continuum SMG phase. Furthermore, the RG flows are consistent with a $\beta$-function that vanishes quadratically at the new fixed point suggesting that the $N_f=4$ flavor SU(2) gauge theory lies at the opening of the conformal window.