Magnetic Moment of Leptons

We show that the magnetic moment of leptons is significantly modified in thermal background as compared to the corresponding vacuum value. We compare the magnetic moment of all different leptons near nucleosynthesis. It is shown that the significance of thermal corrections depends on the temperature of the universe and the respective lepton mass. In the early universe, particle mass was growing quadratically with temperature which affects the corresponding value of magnetic moment. Intrinsic magnetic moment is inversely proportional to mass whereas thermal corrections to the neutrino dipole moment is proportional to neutrino mass for the Dirac type neutrino in the minimal standard model. Therefore the effect of temperature is not the same for charged leptons and neutrinos.