Fri - 02/21/25

There is no new related paper today

There is no new related paper today

  1. [] - Title: Zooming into the horizon region of black hole-type objects - Jesse Daas, Cristobal Laporte, Frank Saueressig, Tim van Dijk

Thu - 02/20/25

**Title:

      Late-time cosmic acceleration from quantum gravity**  - **Authors:** Daniele Oriti, Xiankai Pang  - **Subjects:** 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/](https://arxiv.org/abs/)  - **Abstract**  We deepen the analysis of the cosmological acceleration produced by quantum gravity dynamics in the formalism of group field theory condensate cosmology, treated at the coarse-grained level via a phenomenological model, in the language of hydrodynamics on minisuperspace. Specifically, we conduct a detailed analysis of the late-time evolution, which shows a phantom-like phase followed by an asymptotic De Sitter expansion. We argue that the model indicates a recent occurrence of the phantom crossing and we extract a more precise expression for the effective cosmological constant, linking its value to other parameters in the model and to the scale of the quantum bounce in the early universe evolution. Additionally, we show how the phantom phase produced by our quantum gravity dynamics increases the inferred value of the current Hubble parameter based on observed data, indicating a possible quantum gravity mechanism for alleviating the Hubble tension. Our results represent a concrete example of how quantum gravity can provide an explanation for large-scale cosmological puzzles, in an emergent spacetime scenario.

There is no new related paper today

Wed - 02/19/25

**Title:

      Charged quantum Oppenheimer-Snyder model**  - **Authors:** S. Habib Mazharimousavi  - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc)  - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/)  - **Abstract**  In the framework of loop quantum cosmology, particularly within the quantum Oppenheimer-Snyder model, the semiclassical Ashtekar-Pawlowski-Singh (APS) metric is associated with a static, spherically symmetric black hole that incorporates quantum effects derived from the APS metric. This quantum-corrected black hole can be interpreted as a modified Schwarzschild black hole, where the Schwarzschild metric function is adjusted by an additional term proportional to $\frac{M^{2}}{r^{4}}$, with $r$ denoting the radial coordinate and $M,$ the black hole mass. In this study, we show that such a quantum-mechanically modified black hole can arise in the context of nonlinear electrodynamics with either electric or magnetic charge. This charged, quantum-corrected solution is then matched to a dust ball of constant mass $M_{APS}$, governed by the APS metric, at a timelike thin-shell possessing nonzero mass $m$ and electric charge $Q$ or magnetic charge $P$. Analytically, it is demonstrated that the thin-shell oscillates around an equilibrium radius $r=R_{eq}$, which is expressed in terms of $% M_{APS}$, $m$, and $Q$ or $P$.

There is no new related paper today

Tue - 02/18/25

**Title:

      Lessons from gauge fixing and polymerization of loop quantum black holes with a cosmological constant**  - **Authors:** Geeth Ongole, Parampreet Singh, Anzhong Wang  - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph)  - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/)  - **Abstract**  Loop quantization of Schwarzschild black holes with a cosmological constant for polymerization parameters which are constant is studied in the effective spacetime description. We show that for the positive cosmological constant there can be an appearance of large quantum effects at small spacetime curvatures. These effects can manifest as an additional black hole horizon. While the central singularity is resolved in all the cases, these limitations demonstrate incompatibility of the Kantowski-Sachs gauge and schemes with fixed polymerization parameters in the presence of a positive cosmological constant. In contrast, the case of a negative cosmological constant is free of such problematic features. Noted limitations are similar to those in the $\mu_o$ scheme for the loop quantization of cosmological models.

There is no new related paper today

  1. [] - Title: Simpler Embeddings of Causal Sets into Minkowski Spacetime - Steven Johnston

Mon - 02/17/25

**Title:

      The Statistical Mechanics of Hawking Radiation**  - **Authors:** Noah M. MacKay  - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph)  - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/)  - **Abstract**  Hawking radiation and black hole thermodynamics are well understood in the frameworks of quantum field theory and general relativity, with contemporary extensions in string theory, AdS/CFT, and loop quantum gravity. However, an open question remains: \textit{Can Hawking radiation be consistently described using statistical mechanics?} This challenge arises due to the ambiguous quantum nature of Hawking particles and constraints from information conservation. This study develops a heuristic statistical model, treating Hawking particles as timelike with an effective mass and obeying any statistical distribution. The flow of information is modeled as a transfer of microstates from the event horizon to the radiation background within a closed ensemble. From this, we obtain the Hawking particle mass $m_H=\hbar/(2\pi r_S)$ and the system energy of the black hole as its thermal energy: $E=\hbar/(8\pi GM)$. Beyond preserving conventional insights, reinforcing the statistical nature of black hole evaporation, this approach introduces novel perspectives: modeling the black hole as a structured energy well containing microstates, quantifying the evaporation rate of individual microstates, and determining the total number of microstates from the horizon surface area. This study leaves the door open for a stochastic mechanical analysis, which is introduced in the Discussion section.

There is no new related paper today

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