Stability of SU (Nc) QCD3 from the μ -expansion

QCD with gauge group SU(Nc) flows to an interacting conformal fixed point in three spacetime dimensions when the number of four-component Dirac fermions Nf Nc. We study the perturbative stability of this fixed point via the ϵ-expansion about four dimensions. We find that when the number of fermions is lowered to Nfcrit≈112Nc+(6+4Nc)ϵ, a certain four-fermion operator becomes relevant and the theory flows to a new infrared fixed point that may be either massless or massive. F-theorem or entanglement monotonicity considerations complement our ϵ-expansion calculation.