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New spinfoam vertex for quantum gravity
- E. Livine, Simone Speziale
- Physics
- 4 May 2007
We introduce a new spinfoam vertex to be used in models of 4d quantum gravity based on SU(2) and SO(4) BF theory plus constraints. It can be seen as the conventional vertex of SU(2) BF theory, the…
Polyhedra in loop quantum gravity
- Eugenio Bianchi, P. Donà, Simone Speziale
- Physics
- 17 September 2010
Interwiners are the building blocks of spin-network states. The space of intertwiners is the quantization of a classical symplectic manifold introduced by Kapovich and Millson. Here we show that a…
Twisted geometries: A geometric parametrisation of SU(2) phase space
- L. Freidel, Simone Speziale
- Mathematics
- 15 January 2010
A cornerstone of the loop quantum gravity program is the fact that the phase space of general relativity on a fixed graph can be described by a product of SU(2) cotangent bundles per edge. In this…
Area?angle variables for general relativity
- B. Dittrich, Simone Speziale
- Mathematics, Physics
- 6 February 2008
We introduce a modified Regge calculus for general relativity on a triangulated four-dimensional Riemannian manifold where the fundamental variables are areas and a certain class of angles. These…
Consistently Solving the Simplicity Constraints for Spinfoam Quantum Gravity
- E. Livine, Simone Speziale
- Physics
- 14 August 2007
We give an independent derivation of the Engle-Pereira-Rovelli spinfoam model for quantum gravity which recently appeared in [arXiv:0705.2388]. Using the coherent state techniques introduced earlier…
Self-energy and vertex radiative corrections in LQG
- C. Perini, C. Rovelli, Simone Speziale
- Physics
- 9 October 2008
SU(2) graph invariants, Regge actions and polytopes
- P. Donà, M. Fanizza, Giorgio Sarno, Simone Speziale
- Mathematics
- 5 August 2017
We revisit the the large spin asymptotics of 15j symbols in terms of cosines of the 4d Euclidean Regge action, as derived by Barrett and collaborators using a saddle point approximation. We bring it…
Twistors to twisted geometries
- L. Freidel, Simone Speziale
- Mathematics
- 1 June 2010
In a previous paper we showed that the phase space of loop quantum gravity on a fixed graph can be parametrized in terms of twisted geometries, quantities describing the intrinsic and extrinsic…
Reconcile Planck scale discreteness and the Lorentz-Fitzgerald contraction
- C. Rovelli, Simone Speziale
- Physics
- 25 May 2002
A Planck-scale minimal observable length appears in many approaches to quantum gravity. It is sometimes argued that this minimal length might conflict with Lorentz invariance, because a boosted…
Numerical study of the Lorentzian Engle-Pereira-Rovelli-Livine spin foam amplitude
- P. Donà, M. Fanizza, Giorgio Sarno, Simone Speziale
- MathematicsPhysical Review D
- 29 March 2019
The Lorentzian EPRL spin foam amplitude for loop quantum gravity is a multi-dimensional non-compact integral of highly oscillating functions. Using a method based on the decomposition of…
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