Anomalous low-temperature thermodynamics of QCD in strong magnetic fields

Understand

The thermodynamics of quantum chromodynamics at low temperatures and in sufficiently strong magnetic fields is governed by neutral pions.

• We analyze the interacting system of neutral pions and photons at zero baryon chemical potential using effective field theory.
• As a consequence of the axial anomaly and the external magnetic field, the pions and photons mix with one another.
• The resulting spectrum contains one usual, relativistic photon state, and two nonrelativistic modes, one of which is gapless and the other gapped.