Gliding Down the QCD Transition Line, from Nf=2 till the Onset of Conformality

We review the hot QCD transition with varying number of flavours, from two till the onset of the conformal window. We discuss the universality class for N-f = 2, along the critical line for two massless light flavours, and a third flavour whose mass serves as an interpolator between N-f = 2 and N-f = 3. We identify a possible scaling window for the 3D O(4) universality class transition, and its crossover to a mean field behaviour. We follow the transition from N-f = 3 to larger N-f, when it remains of first order, with an increasing coupling strength; we summarise its known properties, including possible cosmological applications as a model for a strong electroweak transition. The first order transition, and its accompanying second order endpoint, finally morphs into the essential singularity at the onset of the conformal window, following the singular behaviour predicted by the functional renormalisation group.

Automated summary

The study focuses on the hot QCD transition with varying number of flavours, exploring different universality classes and the transition from scaling window to mean field behavior. It summarizes the properties of the transition process, including first order transitions, cosmological applications, and the essential singularity at the onset of the conformal window predicted by the functional renormalisation group.