Quark condensation in quantum chromodynamics

Abstract

Working within a limited Fock-space approximation (LFSA), we argue that if the running coupling constant of quantum chromodynamics (QCD) exceeds a critical value of order 1 the vacuum becomes a condensate of quark-antiquark pairs. To evaluate the critical coupling constant we use a Mellin-transform technique which is first illustrated with a Schr\"odinger equation problem. We then apply it to scalar and spinor QED, as well as to QCD, using the LFSA.