Fri - 10/17/25

**Title:

      Quantum Damping of Cosmological Shear: A New Prediction from Loop Quantum Cosmologies**  - **Authors:** Wen-Cong Gan, Leila L. Graef, Rudnei O. Ramos, Gustavo S. Vicente, Anzhong Wang  - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)  - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/)  - **Abstract**  We analyze the dynamics of the Bianchi I universe in modified loop quantum cosmology (Model I, or mLQC-I), uncovering a robust mechanism for isotropization. As in the standard LQC, the classical singularities are resolved by quantum bounce. Remarkably, mLQC-I exhibits a distinctive feature: following the bounce, the shear is dynamically suppressed and decays rapidly to zero within the deep quantum regime. This occurs independently of the collapsing matter fields, leading to a natural quantum isotropization. Consequently, the three spatial directions expand rapidly to macroscopic scales, producing a homogeneous and isotropic universe directly from the quantum epoch without fine-tuning. Our findings demonstrate that mLQC-I not only resolves singularities but also provides a more effective pathway for suppressing anisotropies than other models, thereby reinforcing its viability as a description of the early universe.

There is no new related paper today

Thu - 10/16/25

**Title:

      Primordial magnetogenesis in loop quantum cosmology**  - **Authors:** Ganga R. Nair, V. Sreenath  - **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**  Primordial magnetic fields (PMFs) are magnetic fields generated during the early universe. These fields are thought to be the seeds of extragalactic magnetic fields. The origin of PMFs is not well known. Further, if they are indeed sources of extragalactic fields, then there is a possibility that observations of extragalactic magnetic fields could provide insights into the primordial physics. With this motivation, we study the generation of the primordial magnetic field in the context of loop quantum cosmology (LQC). In LQC, inflation is preceded by a quantum bounce. In this work, we consider an electromagnetic field coupled to the background as a test field and study its evolution through the bounce and through the subsequent inflationary phase. We investigate the power spectra generated in LQC and show that it is scale-dependent. We study the power spectra with different initial conditions, discuss equivalent forms of coupling functions, investigate backreaction, and compute the amount of primordial magnetic field which can be measured today. We conclude the article with a summary and discussion of the results.

There is no new related paper today

  1. [] - Title: Singularity avoidance in black hole interiors by quantum gravity effects - Takeshi Chiba, Hiroki Matsui, Keiju Murata

Wed - 10/15/25

**Title:

      Information paradox and island of covariant black holes in LQG**  - **Authors:** Yongbin Du, Jia-Rui Sun, Xiangdong Zhang  - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc)  - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/)  - **Abstract**  We study information paradox of four dimensional covariant black holes inspired by loop quantum gravity (LQG) with two well motivated solutions. We first prepare the spacetime in the Hartle-Hawking state, compute the radiation entropy and recover a linear growth at late time. When considering the mass loss and incorporating greybody factors, we show that for Solution~1 the LQG parameter $\zeta$ leaves temperature and Planckian factor of the spectrum unchanged but enhances the near-horizon barrier, leading to a faster evaporation rate as $M$ decreases. This behavior contrasts sharply with Solution~2, which has slow evaporation rate at small $M$ and admits a non-singular continuation suggestive of a remnant or a black-to-white-hole transition. We then apply the island prescription on the eternal background and find that quantum extremal surfaces exist in solution 1 geometries; $\zeta$ primarily shifts the island boundary and suppresses the late time entropy growth, preserving unitarity. Our results highlight that covariance-respecting LQG black hole do not exhibit a universal late time behavior.

**Title:

      Hessian in the spinfoam models with cosmological constant**  - **Authors:** Wojciech Kamiński, Qiaoyin Pan  - **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**  In this paper, we introduce a general method to prove the non-degeneracy of the Hessian in the spinfoam vertex amplitude for quantum gravity and apply it to the spinfoam models with a cosmological constant ($\Lambda$-SF models). By reformulating the problem in terms of the transverse intersection of some submanifolds in the phase space of flat ${\rm SL}(2,\mathbb{C})$ connections, we demonstrate that the Hessian is non-degenerate for critical points corresponding to non-degenerate, geometric 4-simplices in de Sitter or anti-de Sitter space. Non-degeneracy of the Hessian is an important necessary condition for the stationary phase method to be applicable. With a non-degenerate Hessian, this method not only confirms the connection of the $\Lambda$-SF model to semiclassical gravity, but also shows that there are no dominant contributions from exceptional configurations as in the Barrett-Crane model. Given its general nature, we expect our criterion to be applicable to other spinfoam models under mild adjustments.

Tue - 10/14/25

There is no new related paper today

There is no new related paper today

  1. [] - Title: Yukawa interactions in Quantum Gravity - Gustavo P. de Brito, Manuel Reichert, Marc Schiffer

Mon - 10/13/25

There is no new related paper today

There is no new related paper today

  1. [] - Title: Yukawa interactions in Quantum Gravity - Gustavo P. de Brito, Manuel Reichert, Marc Schiffer

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