Strings as perturbations of evolving spin networks
Abstract
One step in the construction of a background independent formulation of string theory is detailed, in which it is shown how perturbative strings may arise as small fluctuations around histories in a formulation of nonperturbative dynamics of spin networks due to Markopoulou. In this formulation the dynamics of spin network states and their generalizations is described in terms of histories which have discrete analogues of the causal structure and many fingered time of Lorentzian spacetimes. Perturbations of these histories turn out to be described in terms of spin systems defined on 2dimensional timelike surfaces embedded in the discrete spacetime. When the history has a classical limit which is Minkowski spacetime, the action of the perturbation theory is given to leading order by the spacetime area of the surface, as in bosonic string theory. This map between a nonperturbative formulation of quantum gravity and a 1+1 dimensional theory generalizes to a large class of theories in which the group SU(2)_is extended to any quantum group or supergroup. It is argued that a necessary condition for the nonperturbative theory to have a good classical limit is that the resulting 1+1 dimensional theory defines a consistent and stable perturbative string theory.
 Publication:

Nuclear Physics B Proceedings Supplements
 Pub Date:
 June 2000
 DOI:
 10.1016/S09205632(00)007581
 arXiv:
 arXiv:hepth/9801022
 Bibcode:
 2000NuPhS..88..103S
 Keywords:

 High Energy Physics  Theory;
 General Relativity and Quantum Cosmology
 EPrint:
 Latex, 18 pages, no figures