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Deforming the algebra of constraint is a well-known approach to effective loop quantum cosmology. More generally, it is a consistent way to modify gravity from the Hamiltonian perspective. In this framework, the Hamiltonian (scalar)…

General Relativity and Quantum Cosmology · Physics 2026-02-16 Jamy-Jayme Thézier , Aurélien Barrau , Killian Martineau , Maxime De Sousa

Loop quantum cosmology (LQC) provides promising resolutions to the trans-Planckian issue and initial singularity arising in the inflationary models of general relativity. In general, due to different quantization approaches, LQC involves…

General Relativity and Quantum Cosmology · Physics 2015-12-10 Tao Zhu , Anzhong Wang , Gerald Cleaver , Klaus Kirsten , Qin Sheng , Qiang Wu

This Chapter provides an up to date, pedagogical review of some of the most relevant advances in loop quantum cosmology. We review the quantization of homogeneous cosmological models, their singularity resolution and the formulation of…

General Relativity and Quantum Cosmology · Physics 2015-06-15 Ivan Agullo , Alejandro Corichi

Loop quantum gravity introduces two characteristic modifications in the classical constraints of general relativity: the holonomy and inverse-triad corrections. In this paper, a systematic construction of anomaly-free effective constraints…

General Relativity and Quantum Cosmology · Physics 2022-08-12 Asier Alonso-Bardaji , David Brizuela

A consistent implementation of quantum gravity is expected to change the familiar notions of space, time and the propagation of matter in drastic ways. This will have consequences on very small scales, but also gives rise to correction…

General Relativity and Quantum Cosmology · Physics 2009-08-26 Martin Bojowald , Golam Mortuza Hossain , Mikhail Kagan , S. Shankaranarayanan

We study spherical charged black holes in the presence of a cosmological constant with corrections motivated by the theory of loop quantum gravity. The effective theory is constructed at the Hamiltonian level by introducing certain…

General Relativity and Quantum Cosmology · Physics 2023-04-12 Asier Alonso-Bardaji , David Brizuela , Raül Vera

Euclidean gravity provides an interesting test system for an analysis of cosmological perturbations in an effective Hamiltonian constraint with holonomy modifications from loop quantum gravity. This paper presents a discussion of scalar…

General Relativity and Quantum Cosmology · Physics 2018-11-21 Jian-Pin Wu , Martin Bojowald , Yongge Ma

We study the tensor modes of linear metric perturbations within an effective framework of loop quantum cosmology. After a review of inverse-volume and holonomy corrections in the background equations of motion, we solve the linearized…

General Relativity and Quantum Cosmology · Physics 2012-07-24 Gianluca Calcagni , Golam Mortuza Hossain

We derive the dynamics of (isotropic) scalar perturbations from the mean-field hydrodynamics of full Lorentzian quantum gravity, as described by a two-sector (timelike and spacelike) Barrett-Crane group field theory (GFT) model. The rich…

General Relativity and Quantum Cosmology · Physics 2024-04-02 Alexander F. Jercher , Luca Marchetti , Andreas G. A. Pithis

With a well-motivated extension of higher order holonomy corrections, the quantum theory of loop quantum cosmology (LQC) for the $k=0$ Friedmann-Robertson-Walker model (with a free massless scalar) is rigorously formulated. The analytical…

General Relativity and Quantum Cosmology · Physics 2009-08-18 Dah-Wei Chiou , Li-Fang Li

Quantum effects are expected to modify the cosmological dynamics of the early universe while maintaining some (potentially discrete) notion of space-time structure. In one approach, loop quantum cosmology, current models are shown here to…

General Relativity and Quantum Cosmology · Physics 2026-04-29 Martin Bojowald , Manuel Diaz , Erick I. Duque

The cosmological tensor perturbation equation with generalized holonomy corrections is derived in the framework of effective loop quantum gravity. This results in a generalized dispersion relation for gravitational waves, encompassing…

General Relativity and Quantum Cosmology · Physics 2024-08-13 Shulan Li , Jian-Pin Wu

We study the dynamics of gauge-invariant scalar perturbations in cosmological scenarios with a modified Friedmann equation, such as quantum gravity bouncing cosmologies. We work within a separate universe approximation which captures…

General Relativity and Quantum Cosmology · Physics 2023-03-02 Steffen Gielen , Lisa Mickel

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 cosmological primordial power spectrum is known to be one of the most promising observable to probe quantum gravity effects. In this article, we investigate how the tensor power spectrum is modified by Loop Quantum Gravity corrections.…

General Relativity and Quantum Cosmology · Physics 2010-04-06 J. Grain , T. Cailleteau , A. Barrau , A. Gorecki

Canonical quantum gravity provides insights into the quantum dynamics as well as quantum geometry of space-time by its implications for constraints. Loop quantum gravity in particular requires specific corrections due to its quantization…

General Relativity and Quantum Cosmology · Physics 2015-05-14 Martin Bojowald

Cosmological perturbation equations are derived systematically in a canonical scheme based on Ashtekar variables. A comparison with the covariant derivation and various subtleties in the calculation and choice of gauges are pointed out.…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Martin Bojowald , Hector H. Hernández , Mikhail Kagan , Parampreet Singh , Aureliano Skirzewski

Emergent modified gravity provides a covariant, effective framework for obtaining spherically symmetric black hole solutions in models of loop quantum gravity with scale-dependent holonomy modifications. Exact solutions for vacuum black…

General Relativity and Quantum Cosmology · Physics 2024-07-18 Idrus Husin Belfaqih , Martin Bojowald , Suddhasattwa Brahma , Erick I. Duque

Scalar cosmological perturbations in loop quantum cosmology (LQC) is revisited in a covariant manner, using self dual Ashtekar variables. For real-valued Ashtekar-Barbero variables, this `deformed algebra' approach has been shown to…

General Relativity and Quantum Cosmology · Physics 2016-10-25 Jibril Ben Achour , Suddhasattwa Brahma , Julien Grain , Antonino Marciano

Gauge invariance of scalar perturbations is studied together with the associated equations of motion. Extending methods developed in the framework of hamiltonian General Relativity, the Hamilton-Jacobi equation is investigated into the…

General Relativity and Quantum Cosmology · Physics 2012-11-01 Thomas Cailleteau , Aurelien Barrau