Electromagnetic field at Finite Temperature: A first order approach
  In this work we study the electromagnetic field at Finite Temperature via the massless DKP formalism. The constraint analysis is performed and the partition function for the theory is constructed and computed. When it is specialized to the spin 1 sector we obtain the well-known result for the thermodynamic equilibrium of the electromagnetic field. 
R. Casana, B. M. Pimentel and J. S. Valverde