  We report the existence, and study mobility and interactions of gap polariton
solitons in a microcavity with a periodic potential, where the light field is
strongly coupled to excitons. Gap solitons are formed due to the interplay
between the repulsive exciton-exciton interaction and cavity dispersion. The
analysis is carried out in an analytical form, using the coupled-mode (CM)
approximation, and also by means of numerical methods.
