Scaling dimensions in QED3 from the ε-expansion

We study the fixed point that controls the IR dynamics of QED in d = 4 − 2ε dimensions. We derive the scaling dimensions of four-fermion and bilinear operators beyond leading order in the ε-expansion. For the four-fermion operators, this requires the computation of a two-loop mixing that was not known before. We then extrapolate these scaling dimensions to d = 3 to estimate their value at the IR fixed point of QED3 as function of the number of fermions Nf. The next-to-leading order result for the four-fermion operators corrects significantly the leading one. Our best estimate at this order indicates that they do not cross marginality for any value of Nf , which would imply that they cannot trigger a departure from the conformal phase. For the scaling dimensions of bilinear operators, we observe better convergence as we increase the order. In particular, the ε-expansion provides a convincing estimate for the dimension of the flavor-singlet scalar in the full range of Nf.