Archived weekly pre-prints 23-03-20

Authors: Rodolfo Gambini, Jorge Pullin
Subjects: General Relativity and Quantum Cosmology (gr-qc)
Arxiv link: https://arxiv.org/abs/2303.09392
Abstract The inclusion of matter fields in spherically symmetric loop quantum gravity has proved problematic at the level of implementing the constraint algebra including the Hamiltonian constraint. Here we consider the system with the introduction of a clock. Using the Abelianizaton technique we introduced in previous papers in the case of gravity coupled to matter, the system can be gauge fixed and rewritten in terms of a restricted set of dynamical variables that satisfy simple Poisson bracket relations. This creates a true Hamiltonian and therefore one bypasses the issue of the constraint algebra. We show how loop quantum gravity techniques may be applied for the vacuum case and show that the Hamiltonian system reproduces previous results for the physical space of states and the observables of a Schwarzchild black hole.

There is no new related paper today

There is no new related paper today

[2303.08399] - Odd-parity perturbations of the wormhole-like geometries and quasi-normal modes in Einstein-Æther theory - Chao Zhang, Anzhong Wang, Tao Zhu
[2303.08802] - Review of the No-Boundary Wave Function - Jean-Luc Lehners

Authors: Guillem Domènech, Misao Sasaki
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
Arxiv link: https://arxiv.org/abs/2303.07661
Abstract The end state of Hawking evaporation of a black hole is uncertain. Some candidate quantum gravity theories, such as loop quantum gravity and asymptotic safe gravity, hint towards Planck sized remnants. If so, the Universe might be filled with remnants of tiny primordial black holes, which formed with mass $M<10^9\,{\rm g}$. A unique scenario is the case of $M\sim 5\times10^5\,{\rm g}$, where tiny primordial black holes reheat the universe by Hawking evaporation and their remnants dominate the dark matter. Here, we point out that this scenario leads to a cosmological gravitational wave signal at frequencies $\sim 100{\rm Hz}$. Finding such a particular gravitational wave signature with, e.g. the Einstein Telescope, would suggest black hole remnants as dark matter.

Authors: Johanna N. Borissova, Bianca Dittrich
Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
Arxiv link: https://arxiv.org/abs/2303.07367
Abstract Lorentzian quantum gravity is believed to cure the pathologies encountered in Euclidean quantum gravity, such as the conformal factor problem. We show that this is the case for the Lorentzian Regge path integral expanded around a flat background. We illustrate how a subset of local changes of the triangulation, so-called Pachner moves, allow to isolate the indefinite nature of the gravitational action at the discrete level. The latter can be accounted for by oppositely chosen deformed contours of integration. Moreover, we construct a discretization-invariant local path integral measure for 3D Lorentzian Regge calculus and point out obstructions in defining such a measure in 4D. We see the work presented here as a first step towards establishing the existence of the non-perturbative Lorentzian path integral for Regge calculus and related frameworks such as spin foams. An extensive appendix provides an overview of Lorentzian Regge calculus, using the recently introduced concept of the complexified Regge action, and derives useful geometric formulae and identities needed in the main text.

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[2303.06563] - Angular spectrum of quantum fluctuations in causal structure - Craig Hogan, Ohkyung Kwon, Nathaniel Selub
[2303.06633] - The case of Quantum Gravity with Spontaneous Collapse of the Wave Function - Lajos Diósi
[2303.07198] - Generalized Uncertainty Principle from the Regularized Self-Energy - Kimet Jusufi, Ahmed Farag Ali

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