The bath spectral function provides a constraint in the choice of the coefficients C i . When this function has the form J ( ω ω ) = η η ω ω , the corresponding classical kind of dissipation can be shown to be Ohmic. A more generic form is J ( ω ω ) ∝ ∝ ω ω s . In this case, if s > 1 the dissipation is called "super-ohmic", while if s < 1 is sub-ohmic. An example of a super-ohmic bath is the electro-magnetic field under certain circumstances.