Title: Nucleation of pion domain wall in QCD matter
Date: Jun 12, 2025
Time: 14:15 - 15:15
Speaker: Dr. Kentaro Nishimura
Affiliation: Niigata University
Abstract: The Chiral Soliton Lattice (CSL) is a periodic structure of parallel domain walls spaced at equal intervals. It becomes energetically favorable in the presence of a background magnetic field and a finite chemical potential due to a topological term arising from the chiral anomaly. We investigate the formation of the CSL from the vacuum, modeling it as a layer of domain-wall disks encircled by vortex or string loops within a Nambu–Goto-type effective theory. We demonstrate that domain walls can nucleate via quantum tunneling when the magnetic field is sufficiently strong. We evaluate the nucleation rate and determine the critical magnetic field strength beyond which this rate is no longer exponentially suppressed.

Although the CSL state is energetically more favorable than the vacuum and the nucleation rate increases with a stronger magnetic field, the rate cannot grow large enough to overcome exponential suppression without encountering a tachyonic instability in the charged pion fluctuations.