The basic idea of multi-phase model is using different phases to describe the corresponding components in the galaxy. Such as in our current model, high temperature (> 10^4 K), low density (< 0.1 / cm^3) hot/warm diffuse gas are modeled using the standard SPH method. 

The cold components (cold clouds) are described with the "sticky" particle scheme, in which particles are N-body like and can collide and coagulate. Besides these, stars and dark matters are described as N-body particles. These components can interact with each other. Stars are born in cold clouds, as is suggested by observations. Their feedback will heat the surrounding cold and hot gas, and metal enrich them. Cold clouds and hot gas can exchange mass, momentum and energy by condensation and evaporation.

By dealing these processes carefully, we can get more reasonable result compared with the popular simple single phase model.

People involved: Liu Lei, Rainer Spurzem, Peter Berczik; Gerhard Hensler, Mykola Petrov, Hsi-Yu Schive.