Relation between polymer and Fock excitations

To bridge the gap between background-independent, non-perturbative quantum gravity and low-energy physics described by perturbative field theory in Minkowski spacetime, Minkowskian Fock states are located, analysed and used in the background-independent framework. This approach to the analysis of semiclassical issues is motivated by the recent results of Varadarajan (Varadarajan M and Zapata J A 2000 Class. Quantum Grav. 17 4085-109). As in that work, we use the simpler U(l) example to illustrate our constructions but, in contrast to that work, we formulate the theory in such a way that it can be extended to full general relativity.