Chiral symmetry breaking in three-dimensional quantum electrodynamics as fixed point annihilation

Spontaneous chiral symmetry breaking in three-dimensional ($d=3$) quantum electrodynamics is understood as annihilation of an infrared-stable fixed point that describes the large-N conformal phase by another unstable fixed point at a critical number of fermions N=Nc. We discuss the root of universality of Nc in this picture, together with some features of the phase boundary in the $(d,N)$ plane. In particular, it is shown that as d→4, Nc→0 with a constant slope, our best estimate of which suggests that Nc=2.89 in $d=3$.