Perturbative Confinement in Thermal Yang-Mills Theories Induced by Imaginary Angular Velocity

We perturbatively compute the Polyakov loop potential at high temperature with finite imaginary angular velocity. This imaginary rotation does not violate the causality, and the thermodynamic limit is well defined. We analytically show that the imaginary angular velocity induces the perturbatively confined phase and serves as a new probe to confinement physics. We discuss a possible phase diagram that exhibits adiabatic continuity from the perturbative confinement to the confined phase at low temperature. We also mention subtlety in the analytical continuation from imaginary to real angular velocity by imposing a causality bound.

Massless mode and positivity violation in hot QCD

We calculate the quark self-energy at one-loop level at high temperature, taking into account contributions from both the (chromo)electric scale gT and the (chromo)magnetic scale g^{2}T. While reproducing standard massive excitations due to the electric scale, we uncover a novel massless excitation ascribable to the magnetic scale. The residue of this massless excitation is nonpositive at all temperatures, which consequently gives rise to positivity violation in the quark spectral functions. This demonstrates the profound impact of confinement effects on thermal quark collective excitations, which manifest genuine long-range correlations in the system.