Field-induced axion decay $a \to e^+ e^-$ in plasma
  The axion decay $a \to e^+ e^-$ is investigated in the presence of a plasma and an external magnetic field. The results demonstrate a strong catalyzing influence of medium. The axion lifetime in the magnetic field of order $10^{15}$ G and at the temperature of order 10 MeV is reduced to $10^4$ s. 
N.V. Mikheev, A.Ya. Parkhomenko and L.A. Vassilevskaya