Two photon decay of $\pi^0$ and $\eta$ at finite temperature and density
  A comparative study of the anomalous decays $\pi^0, \eta \to\gamma\gamma$, at finite temperature and at finite density, is performed in the framework of the three--flavor Nambu--Jona-Lasinio. The similarities and differences between both scenarios are discussed. In both cases the lifetimes of these mesons decrease significantly at the critical point, although this might not be sufficient to observe enhancement of these decays in heavy-ion collisions. 
Pedro Costa, M. C. Ruivo, Yu. L. Kalinovsky