Speaker
Description
We explore the QCD vacuum structure, using a novel semiclassical method on $\mathbb{R}^2×T^2$ with ‘t Hooft and baryon magnetic fluxes. In this setup, it is conjectured that no phase transition occurs when the size of $T^2$ is varied (adiabatic continuity). If this holds true, the analysis at small $T^2$ can predict qualitative features of the QCD vacuum structure on $\mathbb{R}^4$.
At small $T^2$, through semiclassical analysis, we derive a 2D effective theory, where the confining vacuum is described as a dilute gas of center vortices. This 2D effective theory yields a plausible $\theta$-dependence of the QCD vacuum. Moreover, the resulting 2D effective theory is analogous to the chiral Lagrangian with a periodicity-extended $\eta'$ meson. This periodicity extension arises from incorporating the gluonic multi-branch structure into the $\eta'$ degrees of freedom, and it improves the consistency of global aspects of the chiral Lagrangian.