Speaker
Description
In large-$N$ gauge theories, evidence has emerged recently that between confined and deconfined phases a partially-deconfined phase can appear, in which only a subset of colours deconfine. The existence of such a phase has implications for the map between degrees of freedom under gauge/gravity duality and black hole phase diagrams, where a counterpart to the partially-deconfined saddle should be present. We investigate properties of partial deconfinement on the field theory side, first considering the partially-deconfined saddle of large-$N$ pure Yang-Mills theory. Here, the colour degrees of freedom split into confined and deconfined sectors. We argue with the use of numerical simulations that a linear confinement potential is generated in the confined sector, implying the formation of flux tubes, whereas the potential is screened in the deconfined sector and behaves instead according to the perimeter law. Furthermore, we find that the onset of partial deconfinement coincides with the breaking of chiral symmetry breaking, providing an order parameter for the partially-deconfined phase. We conjecture that partial deconfinement is accompanied by a unique signature of global symmetry breaking that can serve as an order parameter. As another, cleaner example of this, we show that CP symmetry breaking coincides precisely with the emergence of the partially-deconfined phase in supersymmetry-broken $\mathcal{N} = 1$ super-Yang-Mills with a theta-angle $\theta = \pi$, for both large finite $N$ and the formal large-$N$ limit. Finally, we discuss consequences of these findings for holography, the QCD crossover, and the internal phase structure of neutron stars.
