F. Markopoulou et L. Smolin, QUANTUM GEOMETRY WITH INTRINSIC LOCAL CAUSALITY - ART. NO. 084032, Physical review. D. Particles and fields, 5808(8), 1998, pp. 4032
The space of states and operators for a large class of background inde
pendent theories of quantum spacetime dynamics is defined. The SU(2) s
pin networks of quantum general relativity are replaced by labelled co
mpact two-dimensional surfaces. The space of states of the theory is t
he direct sum of the spaces of invariant tensors of a quantum group G(
q) over all compact (finite genus) oriented 2-surfaces. The dynamics i
s background independent and locally causal. The dynamics constructs h
istories with discrete features of spacetime geometry such as causal s
tructure and multifingered time. For SU(2) the theory satisfies the Be
kenstein bound and the holographic hypothesis is recast in this formal
ism. [S0556-2821(98)04320-3].