Fri - 05/16/25

There is no new related paper today

There is no new related paper today

  1. [] - Title: Regular black holes from Oppenheimer-Snyder collapse - Pablo Bueno, Pablo A. Cano, Robie A. Hennigar, Ángel J. Murcia, Aitor Vicente-Cano

Thu - 05/15/25

**Title:

      Entropy in Loop Quantum Cosmology**  - **Authors:** Alejandro Corichi, Omar Gallegos  - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph)  - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/)  - **Abstract**  The Generalized First Law (GFL) and the Generalized Second Law (GSL) of thermodynamics are searched for effective and alternative cosmic models using the entropy as a function of the apparent area, transforming the effective cosmological model into the standard form in cosmology. The general conditions of the GSL validity are analyzed for the entropy as a general function and for logarithmic corrections to the usual Black Hole entropy. In particular, we study the GFL and the regions where the GSL is valid for an effective Loop Quantum Cosmology model with spatially flat curvature taking every possible value of the logarithmic correction factor. In addition, we explore the possibility of having negative temperature, where the validity conditions for an alternative generalized second law (AGSL) are studied.

There is no new related paper today

Wed - 05/14/25

**Title:

      Cosmological scalar perturbations for a metric reconstructed from group field theory**  - **Authors:** Steffen Gielen, Lisa Mickel  - **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**  While homogeneous cosmologies have long been studied in the group field theory (GFT) approach to quantum gravity, including a quantum description of cosmological perturbations is highly non-trivial. Here we apply a recent proposal for reconstructing an effective spacetime metric in GFT to the case of a metric with small inhomogeneities over a homogeneous background. We detail the procedure and give general expressions for cosmological scalar perturbations defined in terms of the GFT energy-momentum tensor. These include all the scalar components of standard perturbation theory and hence can be used to define gauge-invariant quantities. We compute these perturbations explicitly for a particular Fock coherent state. While it was previously shown that such a state can be interpreted as an approximately flat homogeneous cosmology at late times, here we find that inhomogeneities do not follow the dynamics of general relativity in the semiclassical regime. More specifically, restricting ourselves to a specific coherent state in a simple (free) GFT, we study two types of perturbative GFT modes, squeezed and oscillating modes. For squeezed modes we find perturbation equations with Euclidean signature and a late-time limit that differs from general relativistic perturbation equations. Oscillating modes satisfy different dynamical equations that also differ from those of general relativity, but show a Lorentzian signature. Our analysis should be understood as a first step in understanding cosmological perturbations within the effective GFT metric.

There is no new related paper today

Tue - 05/13/25

There is no new related paper today

There is no new related paper today

  1. [] - Title: Machine learning automorphic forms for black holes - Vishnu Jejjala, Suresh Nampuri, Dumisani Nxumalo, Pratik Roy, Abinash Swain

Mon - 05/12/25

There is no new related paper today

There is no new related paper today

  1. [] - Title: Machine learning automorphic forms for black holes - Vishnu Jejjala, Suresh Nampuri, Dumisani Nxumalo, Pratik Roy, Abinash Swain

New papers last week