In relativistic theories particle number is not conserved (although both lepton and baryon number are). Therefore when discussing the thermodynamics of a quantum field theory one uses the grand canonical formalism: the entropy S is maximised, keeping fixed the ensemble averages E and N of energy and lepton or baryon number. To implement these constraints two Lagrange multipliers are introduced, beta =1/kT and mu the chemical potential.
|Number of pages
|Journal of Physics G: Nuclear and Particle Physics
|Published - Mar 1989