A first analysis regarding matter-dynamical diffeomorphism coupling

A first attempt at adding matter degrees of freedom to the two-dimensional 'vacuum' gravity model presented in Aldaya and Jaramillo (2000 Class. Quantum Grav. 17 1649) is analysed in this paper. Just as in the previous pure gravity case, quantum diffeomorphism operators (constructed from a Virasoro algebra) possess a dynamical content; their gauge nature is recovered only after the classical limit. Emphasis is placed on the new physical modes modelled on an SU(1, 1)-Kac-Moody algebra. The non-trivial coupling to 'gravity' is a consequence of the natural semi-direct structure of the entire extended algebra. A representation associated with the discrete series of the rigid SU(1, 1) algebra is revisited in the light of previously neglected crucial global features which imply the appearance of an SU(1, 1)-Kac-Moody fusion rule, determining the rather entangled quantum structure of the physical system. In the classical limit, an action which explicitly couples gravity and matter modes governs the dynamics.