COLLECTIVE EXCITATIONS IN SUPERCONDUCTORS AND SEMICONDUCTORS IN THE PRESENCE OF A CONDENSED PHASE

We first study the spectrum of the excitonic polaritons in semiconductors in the presence of a condensed phase. With the help of the Hubbard-Stratonovich transformation we propose an exact mapping of the extended Hubbard model onto an excitonic-polariton model describing the light propagation in semiconductors. This approach allows us to derive exact formulas for spin-spin and charge-charge correlation functions for spin-triplet superconductivity.