Fermionic Fixed-Point Structure of Asymptotically Safe QED with a Pauli Term

Abstract

We test the physical viability of a recent proposal for an asymptotically safe modification of quantum electrodynamics (QED), whose ultraviolet physics is dominated by a non-perturbative Pauli spin-field coupling. We focus in particular on its compatibility with the absence of dynamical generation of fermion mass in QED. Studying the renormalization group flow of chiral four-fermion operators and their fixed points, we discover a distinct class of behavior compared to the standard picture of fixed-point annihilation at large gauge couplings and the ensuing formation of chiral condensates. Instead, transcritical bifurcations, where the fixed points merely exchange infrared stability, are observed. Provided that non-chiral operators remain irrelevant, our theory accommodates a universality class of light fermions for $N_{\text{f}} > 1$ irreducible Dirac flavors. On the contrary, in the special case of $N_{\text{f}} = 1$ flavor, this comes only at the expense of introducing one additional relevant parameter.