Results 21 to 30 of about 47,027 (304)
Spin Foam Models of Riemannian Quantum Gravity [PDF]
Classical and Quantum Gravity, 2002 Using numerical calculations, we compare three versions of the Barrett-Crane model of 4-dimensional Riemannian quantum gravity. In the version with face and edge amplitudes as described by De Pietri, Freidel, Krasnov, and Rovelli, we show the partition ...
Alekseev A +34 more
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SPIN FOAMS AS FEYNMAN DIAGRAMS
2001: A Relativistic Spacetime Odyssey, 2003 It has been recently shown that a certain non-topological spin foam model can be obtained from the Feynman expansion of a field theory over a group. The field theory defines a natural ``sum over triangulations'', which removes the cut off on the number of degrees of freedom and restores full covariance.
Michael Reisenberger, Carlo Rovelli
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Coarse graining in spin foam models [PDF]
Classical and Quantum Gravity, 2003 We formulate the problem of finding the low-energy limit of spin foam models as a coarse-graining problem in the sense of statistical physics. This suggests that renormalization group methods may be used to find that limit. However, since spin foams are models of spacetime at Planck scale, novel issues arise: these microscopic models are sums over ...
Fotini Markopoulou
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Spin foams with timelike surfaces [PDF]
Classical and Quantum Gravity, 2010 22 pages, no figures; v2: remarks on operator formalism added in discussion; correction: the spin 1/2 irrep of the discrete series does not appear in the Plancherel ...
Florian Conrady
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The Feynman propagator for spin foam quantum gravity [PDF]
Physical Review Letters, 2004 We link the notion causality with the orientation of the 2-complex on which spin foam models are based. We show that all current spin foam models are orientation-independent, pointing out the mathematical structure behind this independence.
C. Rovelli +12 more
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Spin foam models of matter coupled to gravity [PDF]
Classical and Quantum Gravity, 2002 We construct a class of spin foam models describing matter coupled to gravity, such that the gravitational sector is described by the unitary irreducible representations of the appropriate symmetry group, while the matter sector is described by the finite-dimensional irreducible representations of that group.
Aleksandar Miković
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SPIN FOAM MODELS OF QUANTUM GRAVITY [PDF]
Mathematical, Theoretical and Phenomenological Challenges Beyond the Standard Model, 2005 We give a short review of the spin foam models of quantum gravity, with an emphasis on the Barret-Crane model. After explaining the shortcomings of the Barret-Crane model, we briefly discuss two new approaches, one based on the 3d spin foam state sum invariants for the embedded spin networks, and the other based on representing the string scattering ...
Aleksandar Miković
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Spin foams without spins [PDF]
Classical and Quantum Gravity, 2016 21 pages, 2 ...
Hnybida, J.T., Hnybida, J.T.
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Energies, 2021 The effects of doping manganese ions into a cerium oxide lattice for a thermochemical two-step water-splitting cycle to produce oxygen and hydrogen and new synthesis methods were experimentally investigated.
Hyun-Seok Cho +4 more
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International Journal of Modern Physics D, 2012 The central object of this paper is a holonomy formulation for spin foams. Within this new representation, we analyze three general requirements: locality, composition law and cylindrical consistency. In particular, cylindrical consistency is shown to fix the arbitrary normalization of the vertex amplitude in the case of Euclidean signature.
Claudio Perini, Elena Magliaro
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