Evolution of the quantized field coupled to a thermal bath: a phase space approach

We present an alternative method for describing the evolution of a mode of the quantized electromagnetic field in contact with a finite temperature thermal bath. We use the expansion of the field density operator in terms of coherent states and the related Glauber-Sudarshan \(P\)-function in phase space. The method allows us to obtain analytical expressions of the system's time-evolved \(P\)-function without needing to solve the corresponding master equation.