Speaker
Description
The nature of QCD matter at intermediate temperature and baryon density—beyond the dilute hadronic phase but before the onset of weakly coupled quark matter—is still not well understood. Various theoretical scenarios have been proposed for this regime, including quarkyonic matter and the spaghetti of quarks with glueballs (SQGB), yet systematic theoretical control is difficult: perturbative and effective-theory methods lose reliability at intermediate coupling, and the sign problem blocks lattice Monte Carlo at finite baryon density. In this talk, I review recent theoretical developments on the phase structure and symmetry realization in this regime. As a concrete first-principles example, I discuss two-color, single-flavor QCD in (1+1) dimensions, studied via uniform matrix product states, which are free of the sign problem. This setup reveals chiral symmetry realization patterns, a gapless Tomonaga–Luttinger liquid phase, and an equation of state approaching free-quark behavior at high density, shedding light on the quarkyonic and SQGB scenarios for the broader QCD phase diagram.