We propose a new systematic approach that allows one to derive the spin foam (state sum) model of a theory starting from the corresponding classical action functional. It can be applied to any theoryâ€¦ (More)

We study the no gravity limit GN â†’ 0 of the Ponzano-Regge amplitudes with massive particles and show that we recover in this limit Feynman graph amplitudes (with Hadamard propagator) expressed as anâ€¦ (More)

We show that the â‹†-product for U(su2), group Fourier transform and effective action arising in [1] in an effective theory for the integer spin Ponzano-Regge quantum gravity model are compatible withâ€¦ (More)

We show how spin networks can be described and evaluated as Feynman integrals over an internal space. This description can, in particular, be applied to the so-called simple SO(D) spin networks thatâ€¦ (More)

In this note we study the correspondence between the " Relativistic Spin Foam " model introduced by Barrett, Crane and Baez and the so(4) Pleban-ski action. We argue that the so(4) Plebanski model isâ€¦ (More)

We show that the effective dynamics of matter fields coupled to 3D quantum gravity is described after integration over the gravitational degrees of freedom by a braided noncommutative quantum fieldâ€¦ (More)

We provide a complete solution of closed strings propagating in NappiWitten space. Based on the analysis of geodesics we construct the coherent wavefunctions which approximate as closely as possibleâ€¦ (More)

We discuss the issue of parity violation in quantum gravity. In particular, we study the coupling of fermionic degrees of freedom in the presence of torsion and the physical meaning of the Immirziâ€¦ (More)

A â€˜2-groupâ€™ is a category equipped with a multiplication satisfying laws like those of a group. Just as groups have representations on vector spaces, 2-groups have representations on â€˜2-vectorâ€¦ (More)