Phase-space method without large-Nscaling for the laser and optical bistability

In the following we present a new set of phase-space equations, based on Haken's laser model, for dealing with atom-cavity situations such as the laser or optical bistability. The most important feature of these equations is that they do not require a scaling in terms of the number of atoms to obtain results, and hence can be used in few-atom situations outside the applicability of other equations. There is a mathematical emphasis in the paper as we develop our equations, but we also use the equations to determine the leading noise terms for the one-atom laser as well as outlining their possible usage in other problems.