Renormalization of symmetry restricted spin foam models with curvature in the asymptotic regime

Bähr, Benjamin; Rabuffo, Giovanni; Steinhaus, Sebastian

doi:10.1103/physrevd.98.106026

Cited by 37 publications

(40 citation statements)

References 80 publications

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“…How they run is a difficult question, which will eventually have to be answered by a derivation of effective equations from full loop quantum gravity, based on the form and dynamical behavior of discrete states. (Only limited information is currently available on this question in loop quantum gravity, for instance from studies of renormalization in this setting [52,53,54,55,56,57].) Even though the construction of such a complete effective theory remains out of reach, the sketch given here demonstrates that a dependence of physical parameters on the infrared scale is only a problem of pure minisuperspace models in which the infrared scale is unknown.…”

Section: A Good Run Of Loop Quantum Cosmologymentioning

confidence: 98%

Critical Evaluation of Common Claims in Loop Quantum Cosmology

Bojowald

2020

Universe

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A large number of models have been analyzed in loop quantum cosmology, using mainly minisuperspace constructions and perturbations. At the same time, general physics principles from effective field theory and covariance have often been ignored. A consistent introduction of these ingredients requires substantial modifications of existing scenarios. As a consequence, none of the broader claims made mainly by the Ashtekar school -such as the genericness of bounces with astonishingly semiclassical dynamics, robustness with respect to quantization ambiguities, the realization of covariance, and the relevance of certain technical results for potential observations -hold up to scrutiny. Several useful lessons for a sustainable version of quantum cosmology can be drawn from this outcome. * e-mail address: bojowald@gravity.psu.edu 1 All quotations from [1] given in this paper refer to the second preprint version.

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Section: A Good Run Of Loop Quantum Cosmologymentioning

confidence: 98%

Critical Evaluation of Common Claims in Loop Quantum Cosmology

Bojowald

2020

Universe

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“…This might allow one to identify relevant and irrelevant geometric variables, which would also be useful for coarse graining other theories, e.g. spin foam models [87][88][89][90][91][92].…”

Section: Discussionmentioning

confidence: 99%

Holographic description of boundary gravitons in (3+1) dimensions

Asante

Dittrich

Haggard

2019

J. High Energ. Phys.

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Gravity is uniquely situated in between classical topological field theories and standard local field theories. This can be seen in the the quasi-local nature of gravitational observables, but is nowhere more apparent than in gravity's holographic formulation. Holography holds promise for simplifying computations in quantum gravity. While holographic descriptions of three-dimensional spacetimes and of spacetimes with a negative cosmological constant are well-developed, a complete boundary description of zero curvature, four-dimensional spacetime is not currently available. Building on previous work in three-dimensions, we provide a new route to four-dimensional holography and its boundary gravitons. Using Regge calculus linearized around a flat Euclidean background with the topology of a solid hyper-torus, we obtain the effective action for a dual boundary theory which describes the dynamics of the boundary gravitons. Remarkably, in the continuum limit and at large radii this boundary theory is local and closely analogous to the corresponding result in threedimensions. The boundary effective action has a degenerate kinetic term that leads to singularities in the one-loop partition function that are independent of the discretization. These results establish a rich boundary dynamics for four-dimensional flat holography. * Electronic address: sasanteATperimeterinstitute.ca † Electronic address: bdittrichATperimeterinstitute.ca ‡ Electronic address: haggardATbard.edu

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“…The global phase of the amplitude depends on the conventions used and on the particular chosen boundary configuration. With the particular choices we made we obtain (21) that is also the expression involved in the well known Biedenharn-Elliott identity (33).…”

Section: Appendices a Derivation Of ∆ 3 Spinfoam Amplitudementioning

confidence: 99%

Searching for classical geometries in spin foam amplitudes: a numerical method

Donà

Gozzini

Sarno

2020

Class. Quantum Grav.

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We develop a numerical method to investigate the semiclassical limit of spin foam amplitudes with many vertices. We test it using the Ponzano-Regge model, a spin foam model for three-dimensional euclidean gravity, and a transition amplitude with three vertices. We study the summation over bulk spins, and we identify the stationary phase points that dominate it and that correspond to classical geometries. We complement with the numerical analysis of a four vertex transition amplitude and with a modification of the model that includes local curvature. We discuss the generalization of our results to the four-dimensional EPRL spin foam model, and we provide suggestions for new computations.

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Renormalization of symmetry restricted spin foam models with curvature in the asymptotic regime

Cited by 37 publications

References 80 publications

Critical Evaluation of Common Claims in Loop Quantum Cosmology

Critical Evaluation of Common Claims in Loop Quantum Cosmology

Holographic description of boundary gravitons in (3+1) dimensions

Searching for classical geometries in spin foam amplitudes: a numerical method

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