The accidental flatness constraint does not mean a wrong classical limit

Article Astronomy & Astrophysics

A high-performance code for EPRL spin foam amplitudes

Francesco Gozzini

Summary: The sl2cfoam-next software library is a high-performance tool for computing Lorentzian EPRL spin foam amplitudes. It significantly improves single-core performance and supports parallelization on multiple CPUs and GPUs. The library has been used to verify Lorentzian single-vertex asymptotics and confirm the presence of the "flatness problem" in spin foam models.

CLASSICAL AND QUANTUM GRAVITY (2021)

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Article Astronomy & Astrophysics

Discrete gravity dynamics from effective spin foams

Seth K. Asante et al.

Summary: This study presents the first computation of spin foam dynamics that acts as a test of the quantum equations of motion of gravity. The results reveal a rich semiclassical regime, but emphasize the need to understand the interplay between various parameters. Additionally, the subtle nature of the semiclassical regime is shown to be a generic feature of path integral quantization of systems with second class constraints.

CLASSICAL AND QUANTUM GRAVITY (2021)

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Article Astronomy & Astrophysics

Addendum to 'EPRL/FK asymptotics and the flatness problem'

J. Engle et al.

Summary: This study shows that removing an approximation used in prior work leads to an improved calculation, resulting in an alternative derivation of the accidental curvature constraint of Hellmann and Kaminski in the studied case. The result is extended to almost all non-degenerate Regge-like boundary data and a wide class of face amplitudes, resolving a tension in the literature.

CLASSICAL AND QUANTUM GRAVITY (2021)

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Article Astronomy & Astrophysics