Fermion bilinear operator critical exponents at $O(1/N^2)$ in the QED-Gross-Neveu universality class

Abstract

We use the critical point large $N$ formalism to calculate the critical exponents corresponding to the fermion mass operator and flavour non-singlet fermion bilinear operator in the universality class of Quantum Electrodynamics (QED) coupled to the Gross-Neveu model for an $SU(N)$ flavour symmetry in $d$-dimensions. The $\epsilon$ expansion of the exponents in $d$ $=$ $4$ $-$ $2\epsilon$ dimensions are in agreement with recent three and four loop perturbative evaluations of both renormalization group functions of these operators. Estimates of the value of the non-singlet operator exponent in three dimensions are provided.