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A discussion is given of recent developments in canonical gravity that assimilates the conformal analysis of gravitational degrees of freedom. The work is motivated by the problem of time in quantum gravity and is carried out at the metric…

General Relativity and Quantum Cosmology · Physics 2014-11-17 Charles H. -T. Wang

For more than 80 years theoretical physicists have been trying to develop a theory of quantum gravity which would successfully combine the tenets of Einstein's theory of general relativity (GR) together with those of quantum field theory.…

General Relativity and Quantum Cosmology · Physics 2019-03-20 Andreas G. A. Pithis

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

We apply the full theory of Loop Quantum Gravity (LQG) to cosmology and present a top-down derivation of gauge-invariant cosmological perturbation theory from quantum gravity. The derivation employs the reduced phase space formulation of…

General Relativity and Quantum Cosmology · Physics 2021-01-20 Muxin Han , Haida Li , Hongguang Liu

We experience some challenges in general gravitational theory owing to Einstein to explain late time acceleration of universe. To address this issue, geometric components of gravity have been modified in quite a few occasions to have a more…

General Relativity and Quantum Cosmology · Physics 2024-10-04 Santanu Das , Nilanjana Mahata , Priyanka Ray

Loop quantum gravity corrections, in the presence of inhomogeneities, can lead to a deformed constraint algebra. Such a deformation implies that the effective theory is no longer generally covariant. As a consequence, the geometrical…

General Relativity and Quantum Cosmology · Physics 2015-06-17 Rakesh Tibrewala

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

This work investigates alternative theories of gravity, the solutions to their field equations and the constraints that can be imposed upon them from observation and experiment. Specifically, we consider the cosmologies and spherically…

General Relativity and Quantum Cosmology · Physics 2007-05-23 T. Clifton

The quantum-reduced loop-gravity technique has been introduced for dealing with cosmological models. We show that it can be applied rather generically: anytime the spatial metric can be gauge-fixed to a diagonal form. The technique selects…

General Relativity and Quantum Cosmology · Physics 2013-11-13 Emanuele Alesci , Francesco Cianfrani , Carlo Rovelli

We present a covariant model of a spherically symmetric black hole with corrections motivated by loop quantum gravity. The effective modifications, parametrized by a positive constant $\lambda$, are implemented through a canonical…

General Relativity and Quantum Cosmology · Physics 2022-10-07 Asier Alonso-Bardaji , David Brizuela , Raül Vera

We prove that the Einstein equations can be solved in a very general form for arbitrary spacetime dimensions and various types of vacuum and non-vacuum cases following a geometric method of anholonomic frame deformations for constructing…

General Relativity and Quantum Cosmology · Physics 2014-11-20 Sergiu I. Vacaru

The fundamental field equations in modified gravity (including general relativity; massive and bimetric theories; Ho\vrava-Lifshits, HL; Einstein--Finsler gravity extensions etc) posses an important decoupling property with respect to…

General Physics · Physics 2014-10-30 Sergiu I. Vacaru

In this article we consider nonholonomic deformations of disk solutions in general relativity to generic off-diagonal metrics defining knew classes of exact solutions in 4D and 5D gravity. These solutions possess Lie algebroid symmetries…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Sergiu I. Vacaru

We propose a new approach to the quasitopological theory of gravity based on a modified classical double--copy construction. Focusing on static, spherically symmetric configurations, we show that all vacuum solutions of $D$--dimensional…

General Relativity and Quantum Cosmology · Physics 2026-01-08 Valeri P. Frolov

We summarize our work on spherically symmetric midi-superspaces in loop quantum gravity. Our approach is based on using inhomogeneous slicings that may penetrate the horizon in case there is one and on a redefinition of the constraints so…

General Relativity and Quantum Cosmology · Physics 2025-05-14 Rodolfo Gambini , Javier Olmedo , Jorge Pullin

A fully consistent linear perturbation theory for cosmology is derived in the presence of quantum corrections as they are suggested by properties of inverse volume operators in loop quantum gravity. The underlying constraints present a…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Martin Bojowald , Golam Mortuza Hossain , Mikhail Kagan , S. Shankaranarayanan

Considering as usual that the underlying geometry of our universe is well described by the spatially flat Friedmann-Lemaitre-Robertson-Walker line element, we review how the background of holonomy corrected Loop Quantum Cosmology (LQC)…

General Relativity and Quantum Cosmology · Physics 2019-05-01 Jaume de Haro , Llibert Aresté Saló , Supriya Pan

In this letter, we investigate cosmology within the framework of modified $f(Q, L_m)$ gravity using the non-linear model $f(Q, L_m) = -Q + \alpha L_m^n + \beta$, where $\alpha$, $\beta$, and $n$ are free parameters. The modified Friedmann…

Cosmology and Nongalactic Astrophysics · Physics 2025-05-02 Y. Myrzakulov , Alnadhief H. A. Alfedeel , M. Koussour , S. Muminov , E. I. Hassan , J. Rayimbaev

In a wide range of quantum gravity theories, quasiclassical geometries, which are solutions to the Einstein field equations approximately, are described by "coherent states." Here we propose a Hamiltonian formalism for gravitational…

General Relativity and Quantum Cosmology · Physics 2025-12-01 Sijia Wang , Achintya Sajeendran , Dong-han Yeom , Robert B. Mann , Joshua Foo

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