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We propose a new derivation from the full Loop Quantum Gravity (LQG) to the Loop Quantum Cosmology (LQC) improved $\bar{\mu}$-scheme effective dynamics, based on the reduced phase space formulation of LQG and a proposal of effective…

General Relativity and Quantum Cosmology · Physics 2020-09-30 Muxin Han , Hongguang Liu

In the context of the geometrical interpretation of the spin network states of Loop Quantum Gravity, we look at the holonomies of the Ashtekar-Barbero connection on loops embedded in space-like hyperboloids. We use this simple setting to…

General Relativity and Quantum Cosmology · Physics 2015-12-23 Christoph Charles , Etera R. Livine

The scheme of using the Chern-Simons action to regularize the gravitational Hamiltonian constraint is extended to including the Lorentzian term in the $k=0$ cosmological model. The Euclidean term and the Lorenzian term are thus regularized…

General Relativity and Quantum Cosmology · Physics 2020-10-12 Jinsong Yang , Cong Zhang , Yongge Ma

We explore the weak-field phenomenology of a compact star spacetime modified by quantum gravitational corrections derived from the effective field theoretical (EFT) approach by Calmet et al. [1]. These corrections, encoded in non-local…

General Relativity and Quantum Cosmology · Physics 2026-02-10 Reggie C. Pantig , Ali Ovgun , Gaetano Lambiase

The first-order loop quantum gravity correction of the simplest, classical general-relativistic Friedmann Hamiltonian constraint, emerging from a holomorphic spinfoam cosmological model peaked on homogeneous, isotropic geometries, is…

General Relativity and Quantum Cosmology · Physics 2015-07-02 Christian Röken

Effective models of quantum black holes inspired by Loop Quantum Gravity (LQG) have had success in resolving the classical singularity with polymerisation procedures and by imposing the LQG area gap as a minimum area. The singularity is…

General Relativity and Quantum Cosmology · Physics 2023-06-19 F. C. Sobrinho , H. A. Borges , I. P. R. Baranov , S. Carneiro

We propose a new $\bar{\mu}$-scheme Hamiltonian effective dynamics in the spherical symmetric sector of Loop Quantum Gravity (LQG). The effective dynamics is generally covariant as derived from a covariant Lagrangian. The Lagrangian belongs…

General Relativity and Quantum Cosmology · Physics 2022-12-12 Muxin Han , Hongguang Liu

We study the dynamics of the scalar modes of linear perturbations around a flat, homogeneous and isotropic background in loop quantum cosmology. The equations of motion include quantum geometry effects and hold at all curvature scales so…

General Relativity and Quantum Cosmology · Physics 2015-05-30 Edward Wilson-Ewing

We develop the quantization of unimodular gravity in the Plebanski and Ashtekar formulations and show that the quantum effective action defined by a formal path integral is unimodular. This means that the effective quantum geometry does not…

High Energy Physics - Theory · Physics 2013-05-29 Lee Smolin

Canonical methods can be used to construct effective actions from deformed covariance algebras, as implied by quantum-geometry corrections of loop quantum gravity. To this end, classical constructions are extended systematically to…

General Relativity and Quantum Cosmology · Physics 2013-05-30 Martin Bojowald , George M. Paily

Based on a recent purely geometric construction of observables for the spatial diffeomorphism constraint, we propose two distinct quantum reductions to spherical symmetry within full 3+1-dimensional loop quantum gravity. The construction of…

General Relativity and Quantum Cosmology · Physics 2015-05-28 Norbert Bodendorfer , Jerzy Lewandowski , Jedrzej Świeżewski

The Janis-Newman-Winicour metric is a solution of Einstein's gravity minimally coupled to a real massless scalar field. The $\gamma$-metric is instead a vacuum solution of Einstein's gravity. These spacetimes have no horizon and possess a…

General Relativity and Quantum Cosmology · Physics 2018-03-08 Hrishikesh Chakrabarty , Carlos A. Benavides-Gallego , Cosimo Bambi , Leonardo Modesto

The Hamiltoinian analysis of the vector-tensor theory of gravity is performed. The resulting geometrical dynamics is reformulated into the connection dynamics, with the real SU(2)-connection serving as one of the configuration variables.…

General Relativity and Quantum Cosmology · Physics 2026-02-24 Shengzhi Li , Yongge Ma

The issue of consistency is crucial in quantum gravity. It has recently been intensively addressed for effective symmetry-reduced models. In this article, we exhaustively study the anomaly freedom of effective loop quantum cosmology with…

General Relativity and Quantum Cosmology · Physics 2024-09-11 Maxime De Sousa , Aurélien Barrau , Killian Martineau

The effective dynamics of the Janis-Newman-Winicour spacetime inspired by loop quantum gravity is studied. Two different schemes are considered to regularize the Hamiltonian constraint for the quantum dynamics. In the $\mu_0$ scheme in…

General Relativity and Quantum Cosmology · Physics 2026-05-05 Faqiang Yuan , Shengzhi Li , Zhen Li , Yongge Ma

In canonical gravity, covariance is implemented by brackets of hypersurface-deformation generators forming a Lie algebroid. Lie algebroid morphisms therefore allow one to relate different versions of the brackets that correspond to the same…

General Relativity and Quantum Cosmology · Physics 2016-11-15 Martin Bojowald , Suddhasattwa Brahma , Umut Buyukcam , Fabio D'Ambrosio

Since there are quantization ambiguities in constructing the Hamiltonian constraint operator in isotropic loop quantum cosmology, it is crucial to check whether the key features of loop quantum cosmology are robust against the ambiguities.…

General Relativity and Quantum Cosmology · Physics 2010-04-14 Jinsong Yang , You Ding , Yongge Ma

We consider the modified Einstein equations obtained in the framework of effective spherically symmetric polymer models inspired by Loop Quantum Gravity. When one takes into account the anomaly free point-wise holonomy quantum corrections,…

General Relativity and Quantum Cosmology · Physics 2019-02-01 Jibril Ben Achour , Frédéric Lamy , Hongguang Liu , Karim Noui

We study the quantization of spherically symmetric vacuum spacetimes within loop quantum gravity. In particular, we give additional details about our previous work in which we showed that one could complete the quantization the model and…

General Relativity and Quantum Cosmology · Physics 2016-12-20 Rodolfo Gambini , Javier Olmedo , Jorge Pullin

Within loop quantum gravity we construct a coarse-grained approximation for the Einstein-Maxwell theory that yields effective Maxwell equations in flat spacetime comprising Planck scale corrections. The corresponding Hamiltonian is defined…

High Energy Physics - Theory · Physics 2009-11-07 Jorge Alfaro , Hugo A. Morales-Técotl , Luis F. Urrutia