Seminarium Teorii Względności i Grawitacji

The system is defined as the domain of dependence of a topological disc with fixed boundary metric. We identify the reduced phase space as an infinite dimensional space of "boundary gravitons". To quantize we apply Isham’s group-theoretic scheme, with respect to a BMS_3 group acting on the phase space. We find that the twist of the diamond boundary loop is quantized in integer or half-integer multiples of the ratio of the Planck length to the boundary length.