Results 21 to 30 of about 45,346 (288)
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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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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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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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 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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Causality in spin foam models [PDF]
Physical Review D, 2000 We compute Teitelboim's causal propagator in the context of canonical loop quantum gravity. For the Lorentzian signature, we find that the resultant power series can be expressed as a sum over branched, colored two-surfaces with an intrinsic causal structure. This leads us to define a general structure which we call a ``causal spin foam''.
Sameer Gupta
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How-to Compute EPRL Spin Foam Amplitudes
Universe, 2022 Spin foam theory is a concrete framework for quantum gravity where numerical calculations of transition amplitudes are possible. Recently, the field became very active, but the entry barrier is steep, mainly because of its unusual language and notions ...
Pietro Donà, Pietropaolo Frisoni
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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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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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