Extended knots and the space of states of quantum gravity

TL;DR

This paper introduces extended loops as a new approach to analyze quantum gravity states, providing analytic tools for knot invariants and Hamiltonian evaluation, advancing the understanding of the space of quantum gravity states.

Contribution

It develops a systematic method to construct analytic diffeomorphism invariants using extended loops, overcoming previous analytic and knot invariant limitations.

Findings

Extended knots relate to ordinary knots formally.

Analytic expressions for knot invariants can be generated systematically.

Hamiltonian evaluation over extended loops is feasible and thorough.

Abstract

In the loop representation the quantum constraints of gravity can be solved. This fact allowed significant progress in the understanding of the space of states of the theory. The analysis of the constraints over loop dependent wavefunctions has been traditionally based upon geometric (in contrast to analytic) properties of the loops. The reason for this preferred way is twofold: for one hand the inherent difficulties associated with the analytic loop calculus, and on the other our limited knowledge about the analytic properties of knots invariants. Extended loops provide a way to overcome the difficulties at both levels. For one hand, a systematic method to construct analytic expressions of diffeomorphism invariants (the extended knots) in terms of the Chern-Simons propagators can be developed. Extended knots are simply related to ordinary knots (at least formally). The analytic expressions of knot invariants could be produced then in a generic way. On the other hand, the evaluation of the Hamiltonian over extended loop wavefunctions can be thoroughly accomplished in the extended loop framework. These two ingredients promote extended loops as a potential resort for answering important questions about quantum gravity.