Archived weekly pre-prints 25-02-17
Fri - 02/14/25
Loop quantum gravity related papers
**Title:
The shadow and accretion disk images of the rotation loop quantum black bounce** - **Authors:** Ke-Jian He, Huan Ye, Xiao-Xiong Zeng, Li-Fang Li, Peng Xu - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc) - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/) - **Abstract** In this paper, we study the shadow and observational image of the Kerr-like Loop Quantum Gravity (LQG) inspired black bounce with the help of the celestial light source and the thin disk source by employing the backward ray-tracing method. The results indicate that both the LQG parameter alpha and the rotation parameter a contribute to a reduction in the shadow size; however, the influence of a is predominant, while the effect of alpha circular orbit. One can find that the correlation parameter (a, alpha), along with the observer's inclination angle, affect the image's asymmetry and the distortion of the inner shadow. As the inclination increases, the direct and lensed images diverge, creating a structure resembling a hat. Meanwhile, we also investigate the redshift distribution of the direct lensed images of the accretion disk under different parameters and observation angle. The results show that the distribution of redshift and observed intensity is obviously related to the behavior of accretion flow. These results may provide a potential approach to limit black hole parameters, detect quantum gravity effects, and distinguish the LQG black hole from other black hole models.
Spin foam related papers
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Other related papers
- [] - Title: Regular black holes in Lovelock with degenerated ground state - Milko Estrada, Bastian Astudillo, Rodrigo Aros
Thu - 02/13/25
Loop quantum gravity related papers
**Title:
The one-loop effective action from the coherent state path integral of loop quantum gravity** - **Authors:** Renata Ferrero, Muxin Han, Hongguang Liu - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th) - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/) - **Abstract** We adopt a novel approach to combine path integral methods with Loop Quantum Gravity (LQG). Our approach builds upon the recently developed coherent state path integral formulation of LQG to compute the one-loop effective action. We compare this methodology with the conventional Quantum Field Theory (QFT) prescription for path integrals and extend the formalism to account for the dependence on boundary (coherent) states. This work aims to explore two aspects: to compare our results with the divergences observed in one-loop calculations of Einstein gravity testing UV-finiteness and to initiate an exploration of the IR effective properties of LQG. We compute the effective action around flat spacetime obtaining analytical and numerical results in the long and short wavelength approximations, respectively. Due to the one-loop dynamics of the LQG area, we find a divergence-free effective action. We study the propagator and the dynamical modes and derive the quantum equation of motion at one loop. We ensure consistency with the semiclassical approximation in the long wavelength limit and, beyond this approximation, analyze numerical scaling as the lattice size increases.
Spin foam related papers
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- [] - Title: Quantum Spacetime Leaps: Higher Dimensional Energetic Causal Sets - Vasco Gil Gomes
Wed - 02/12/25
Loop quantum gravity related papers
**Title:
Stochastic Clocks in ADM-Based Canonical Gravity** - **Authors:** Pradosh Keshav MV - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc) - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/) - **Abstract** The problem of time in canonical quantum gravity remains one of the most significant challenges, primarily due to the ``frozen'' formalism emerging from the Wheeler--DeWitt equation. Within the ADM formalism, we introduce a novel approach in which a scalar field is treated as a stochastic clock. By imposing a divergence-free condition on the scalar momentum, we integrate out quantum gravitational fluctuations and derive an effective noise term via the Hubbard--Stratonovich transformation. This noise drives dynamic adjustments in spacetime foliations, enabling a Schrödinger-like evolution that preserves diffeomorphism invariance and, upon noise averaging, maintains unitary evolution. Interestingly, by introducing stochastic variations in the foliations, the quantum indeterminacy of the clock recasts time as a diffusive process emerging from quantum fluctuations -- where correlations between matter and geometry replace an absolute time parameter. This is considerably a potential pathway for understanding quantum time evolution while maintaining background independence in canonical quantum gravity.
Spin foam related papers
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- [] - Title: Transition from Regular Black Holes to Wormholes in Covariant Effective Quantum Gravity: Scattering, Quasinormal Modes, and Hawking Radiation - R. A. Konoplya, O. S. Stashko
Tue - 02/11/25
Loop quantum gravity related papers
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Spin foam related papers
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- [] - Title: An Airy Tale at Large $N$ - Nikolay Bobev, Pieter-Jan De Smet, Junho Hong, Valentin Reys, Xuao Zhang
Mon - 02/10/25
Loop quantum gravity related papers
**Title:
Black Hole Evaporation in Loop Quantum Gravity** - **Authors:** Abhay Ashtekar - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph); Quantum Physics (quant-ph) - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/) - **Abstract** The conference \emph{Black Holes Inside and Out} marked the 50th anniversary of Hawking's seminal paper on black hole radiance. It was clear already from Hawking's analysis that a proper quantum gravity theory would be essential for a more complete understanding of the evaporation process. This task was undertaken in Loop Quantum Gravity (LQG) two decades ago and by now the literature on the subject is quite rich. The goal of this contribution is to summarize a mainstream perspective that has emerged. The intended audience is the broader gravitational physics community, rather than quantum gravity experts. Therefore, the emphasis is on conceptual issues, especially on the key features that distinguish the LQG approach, and on concrete results that underlie the paradigm that has emerged. This is \emph{not} meant to be an exhaustive review. Rather, it is a broad-brush stroke portrait of the present status. Further details can be found in the references listed.
Spin foam related papers
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