Fermi's golden rule for $N$-body systems in a black-body radiation
  We review the calculation of Fermi's golden rule for a system of $N$-body dipoles, magnetic or electric, weakly interacting with a blackbody radiation. By using the magnetic or electric field-field correlation function evaluated in the 1960s for the black body radiation, we deduce a general formula for the transition rates and study its limiting, fully coherent or fully incoherent, regimes. 
Massimo Ostilli and Carlo Presilla
quant-ph cond-mat.stat-mech math-ph math.MP physics.atom-ph