Thermal pion masses in the second phase: $|\mu_{I}| >m_{\pi}$
  Density and thermal corrections to the mass of the pions are studied in the framework of the SU(2) low energy effective chiral lagrangian, in terms of the isospin chemical potential $\mu_\tin{I}$. We concentrate the discussion in the region where the isospin chemical potential (absolute value) becomes bigger than the pion mass at zero temperature and density, i.e. in the phase where the condensed $\pi^-$ phase appears (for negative chemical potential). We are able to calculate the thermal and density evolution of masses in the limits where $|\mu_{I}|\gg m$ and where $|\mu_{I}| \gtrsim m$. We also identified the phase transition curve. 
M. Loewe and C. Villavicencio