コロキウムのお知らせ

In this talk, I will discuss QCD vacuum in strong magnetic fields. As a first step towards understanding the effects of magnetic fields on QCD vacuum properties, we analytically derive the Euler-Heisenberg action for QCD + QED at zero and finite temperatures. From the action, at zero temperature, we found that the chromo-magnetic field prefers to be parallel to the external magnetic field, and thus the QCD vacuum with strong magnetic fields is spatially anisotropic [1]. This result is consistent with recent lattice data. Furthermore, the chromo-magnetic condensate increases with an increasing magnetic field [1], which supports the "gluonic magnetic catalysis" as observed in current lattice data.

Next, I will discuss the effective potential with strong magnetic fields at finite temperatures [2]. In particular, we focus on the influence of the magnetic field on the center symmetry in QCD. The pure Yang-Mills theory has the center symmetry (being spontaneously broken at high temperature), but dynamical quarks explicitly break it. I will show how the magnetic fields affect the explicit symmetry breaking, by using the effective potential for the Polyakov loop.

References:
[1] S. Ozaki, Phys. Rev. D89, 054022 (2014)
[2] S. Ozaki, T. Arai, K. Hattori and K. Itakura, Phys. Rev. D92, 016002 (2015)