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In the path integral formulation of the reduced phase space Loop Quantum Gravity (LQG), we propose a new approach to allow the spatial cubic lattice (graph) to change dynamically in the physical time evolution. The equations of motion of…

General Relativity and Quantum Cosmology · Physics 2021-07-14 Muxin Han , Hongguang Liu

A new routine is proposed to relate Loop Quant Cosmology (LQC) to Loop Quantum Gravity (LQG) from the perspective of effective dynamics. We derive the big-bang singularity resolution and big bounce from the first principle of full canonical…

General Relativity and Quantum Cosmology · Physics 2020-02-12 Muxin Han , Hongguang Liu

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

We present a systematic study of the cosmological dynamics resulting from an effective Hamiltonian, recently derived in loop quantum gravity using Thiemann's regularization and earlier obtained in loop quantum cosmology (LQC) by keeping the…

General Relativity and Quantum Cosmology · Physics 2018-04-25 Bao-Fei Li , Parampreet Singh , Anzhong Wang

Loop quantum gravity and cosmology are reviewed with an emphasis on evaluating the dynamics, rather than constructing it. The three crucial parts of such an analysis are (i) deriving effective equations, (ii) controlling the theory's…

General Relativity and Quantum Cosmology · Physics 2011-01-31 Martin Bojowald

In loop quantum gravity (LQG), states of the gravitational field are represented by labeled graphs called spin networks. Their dynamics can be described by a Hamiltonian constraint, { which acts on the spin network states modifying both…

General Relativity and Quantum Cosmology · Physics 2025-11-27 Thiago L. M. Guedes , Guillermo A. Mena Marugán , Francesca Vidotto , Markus Müller

The concept of effective dynamics has proven successful in LQC, a loop-inspired quantization of cosmological spacetimes. We apply the same idea of its derivation in LQC to the full theory, by computing the expectation value of the scalar…

General Relativity and Quantum Cosmology · Physics 2018-09-17 Andrea Dapor , Klaus Liegener

We show how Loop Quantum Cosmology can be derived as an effective semiclassical description of Loop Quantum Gravity. Using the tools of QRLG, a gauge fixed version of LQG, we take the coherent states of the fundamental microscopic theory…

General Relativity and Quantum Cosmology · Physics 2014-10-20 Emanuele Alesci , Francesco Cianfrani

Loop quantum gravity is a mature theory. To proceed to explicit calculations in cosmology, it is necessary to make assumptions and simplifications based on the symmetries of the cosmological setting. Symmetry reduction is especially…

General Relativity and Quantum Cosmology · Physics 2016-08-03 Aurélien Barrau , Boris Bolliet

This papers offers a critical discussion on the procedure by which Loop Quantum Cosmology (LQC) is constructed from the full Loop Quantum Gravity (LQG) theory. Revising recent issues in preserving SU(2) symmetry when quantizing the…

General Relativity and Quantum Cosmology · Physics 2015-06-03 Francesco Cianfrani , Giovanni Montani

The implementation of the dynamics in loop quantum gravity (LQG) is still an open problem. Here, we discuss a tentative dynamics for the simplest class of graphs in LQG: Two vertices linked with an arbitrary number of edges. We find an…

General Relativity and Quantum Cosmology · Physics 2015-05-30 Enrique F. Borja , Jacobo Diaz-Polo , Laurent Freidel , Iñaki Garay , Etera R. Livine

We explore how to extract effective dynamics from loop quantum gravity and spinfoams truncated to a finite fixed graph, with the hope of modeling symmetry-reduced gravitational systems. We particularize our study to the 2-vertex graph with…

General Relativity and Quantum Cosmology · Physics 2013-07-09 Etera R. Livine , Mercedes Martín-Benito

In loop quantum cosmology, non-perturbative quantum gravity effects lead to the resolution of the big bang singularity by a quantum bounce without introducing any new degrees of freedom. Though fundamentally discrete, the theory admits a…

General Relativity and Quantum Cosmology · Physics 2010-05-12 Gonzalo J. Olmo , Parampreet Singh

In the lattice approach to Loop Quantum Gravity on a fixed graph computations tend to be involved and are rarely analytically manageable. But, when interested in the expectation values of coherent states on the lattice which are sharply…

General Relativity and Quantum Cosmology · Physics 2021-11-01 Klaus Liegener , Łukasz Rudnicki

As a canonical and generally covariant gauge theory, loop quantum gravity requires special techniques to derive effective actions or equations. If the proper constructions are taken into account, the theory, in spite of considerable…

General Relativity and Quantum Cosmology · Physics 2013-08-02 Martin Bojowald

We review aspects of loop quantum gravity in a pedagogical manner, with the aim of enabling a precise but critical assessment of its achievements so far. We emphasise that the off-shell (`strong') closure of the constraint algebra is a…

High Energy Physics - Theory · Physics 2009-11-11 Hermann Nicolai , Kasper Peeters , Marija Zamaklar

This article presents an "in-a-nutshell" yet self-contained introductory review on loop quantum gravity (LQG) -- a background-independent, nonperturbative approach to a consistent quantum theory of gravity. Instead of rigorous and…

General Relativity and Quantum Cosmology · Physics 2014-12-30 Dah-Wei Chiou

This is a (relatively) non -- technical summary of the status of the quantum dynamics in Loop Quantum Gravity (LQG). We explain in detail the historical evolution of the subject and why the results obtained so far are non -- trivial. The…

High Energy Physics - Theory · Physics 2008-11-26 Thomas Thiemann

This chapter focuses on the status of the implementation of the dynamics in the canonical version of Loop Quantum Gravity (LQG). Concretely this means to provide a mathematical meaning of the quantum Einstein equations, sometimes called…

General Relativity and Quantum Cosmology · Physics 2023-04-03 Thomas Thiemann , Kristina Giesel

An one-parameter regularization freedom of the Hamiltonian constraint for loop quantum gravity is analyzed. The corresponding spatially flat, homogenous and isotropic model includes the two well-known models of loop quantum cosmology as…

General Relativity and Quantum Cosmology · Physics 2021-11-12 Xiangdong Zhang , Gaoping Long , Yongge Ma
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