Nested-open-quantum-systems approach to photonic Bose-Einstein condensation

The photonic Bose-Einstein condensate is a recently observed collective ground state of coupled light-matter system. We describe this quantum based on macroscopic electrodynamics in dispersing and absorbing environments. To model the photon-dye dynamics, we derive master equation using nested-open-quantum-systems approach yielding all parameters essential to condensation process. This allows us photon condensates arbitrary shapes because geometry-dependent decay constants can be expressed terms Green's tensor. In particular, obtain cavity mode absorption emission rates dye molecules.