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Loop Quantum Gravity (LQG) is one of the leading approaches to unify quantum physics and General Relativity (GR). The Hilbert space of LQG is spanned by spin-networks which describe the local geometry of quantum space-time. Simulation of…

General Relativity and Quantum Cosmology · Physics 2021-12-21 Swapnil Nitin Shah

Building on prior work, a generally covariant reformulation of free scalar field theory on the flat Lorentzian cylinder is quantized using Loop Quantum Gravity (LQG) type `polymer' representations. This quantization of the {\em continuum}…

General Relativity and Quantum Cosmology · Physics 2015-01-30 Alok Laddha , Madhavan Varadarajan

We present and analyze a gauge-invariant quantum theory of the Friedmann-Robertson-Walker universe with dust. We construct the reduced phase space spanned by gauge-invariant quantities by using the so-called relational formalism at the…

General Relativity and Quantum Cosmology · Physics 2009-11-10 Fumitoshi Amemiya , Tatsuhiko Koike

We reconsider the Rovelli-Smolin model of gravity coupled to the Klein-Gordon time field with an eye towards capturing the degrees of freedom of the scalar field lost in the framework in which time is deparametrized by the scalar field.…

General Relativity and Quantum Cosmology · Physics 2016-02-03 Jerzy Lewandowski , Hanno Sahlmann

This article sheds new light on the problem of cosmological reduction in Loop Quantum Gravity. We critically analyze Quantum Reduced Loop Gravity -- an attempt to extract the cosmological sector of the full theory. We reconsider the…

General Relativity and Quantum Cosmology · Physics 2021-01-12 Jakub Bilski , Antonino Marciano

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

In [1] we initiated an approach towards quantizing the Hamiltonian constraint in Loop Quantum Gravity (LQG) by requiring that it generates an anomaly-free representation of constraint algebra off-shell. We investigated this issue in the…

General Relativity and Quantum Cosmology · Physics 2014-11-13 Adam Henderson , Alok Laddha , casey Tomlin

Introducing a new method, we demonstrate how the action of reduced operators can be derived without resorting to a recoupling theory and how they exactly reproduce the results obtained in the standard approach of Quantum Reduced Loop…

General Relativity and Quantum Cosmology · Physics 2020-07-07 Jakub Bilski , Antonino Marciano

We analyze the phase space of gravity non-minimally coupled to a scalar field in a generic local Lorentz frame. We reduce the set of constraints to a first-class one by fixing a specific hypersurfaces in the phase space. The main issue of…

General Relativity and Quantum Cosmology · Physics 2013-05-29 F. Cianfrani , G. Montani

We analyze the issue of anomaly-free representations of the constraint algebra in Loop Quantum Gravity (LQG) in the context of a diffeomorphism-invariant gauge theory in three spacetime dimensions. We construct a Hamiltonian constraint…

General Relativity and Quantum Cosmology · Physics 2015-06-04 Adam Henderson , Alok Laddha , Casey Tomlin

Loop Quantum Gravity is a formalism for describing the quantum mechanics of the gravitational field based on the canonical quantization of General Relativity. The most important result of LQG is that geometric quantities such as area and…

General Relativity and Quantum Cosmology · Physics 2019-10-25 W. F. Chagas-Filho

Within the framework of Quantum Reduced Loop Gravity we quantize the Hamiltonian for a gauge vector field. The regularization can be performed using tools analogous to the ones adopted in full Loop Quantum Gravity, while the matrix elements…

General Relativity and Quantum Cosmology · Physics 2017-06-07 Jakub Bilski , Emanuele Alesci , Francesco Cianfrani , Pietro Donà , Antonino Marciano

It is well known that the quantum double structure plays an important role in three dimensional quantum gravity coupled to matter field. In this paper, we show how this algebraic structure emerges in the context of three dimensional…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Karim Noui

We present a new perspective on early cosmology based on Loop Quantum Gravity. We use projected spinnetworks, coherent states and spinfoam techniques, to implement a quantum reduction of the full Kinematical Hilbert space of LQG, suitable…

General Relativity and Quantum Cosmology · Physics 2013-03-05 Emanuele Alesci

In this PhD thesis, we introduced a new strategy to investigate the kinematical and physical predictions of self dual Loop Quantum Gravity (LQG) and by-passed the old problem of implementing quantum mechanically the so called reality…

General Relativity and Quantum Cosmology · Physics 2015-11-24 Jibril Ben Achour

We present a pedagogical introduction to the notions underlying the connection formulation of General Relativity - Loop Quantum Gravity (LQG) - with an emphasis on the physical aspects of the framework. We begin by reviewing General…

General Relativity and Quantum Cosmology · Physics 2017-01-10 Sundance Bilson-Thompson , Deepak Vaid

In order to test the canonical quantization programme for general relativity we introduce a reduced model for a real sector of complexified Ashtekar gravity which captures important properties of the full theory. While it does not…

General Relativity and Quantum Cosmology · Physics 2010-04-06 T. Thiemann

The existing approaches to quantization of gravity aim at giving quantum description of 3-geometry following to the ideas of the Wheeler -- DeWitt geometrodynamics. In this description the role of gauge gravitational degrees of freedom is…

General Relativity and Quantum Cosmology · Physics 2012-05-31 T. P. Shestakova

We present a systematic approach to the kinematics of quantum-reduced loop gravity, a model originally proposed by Alesci and Cianfrani as an attempt to probe the physical implications of loop quantum gravity. We implement the quantum…

General Relativity and Quantum Cosmology · Physics 2024-12-03 Ilkka Mäkinen

This is a brief overview of the current status of symmetry reduced models in Loop Quantum Gravity (LQG), focussing on the very early universe. Over the last 3 years or so the subject has matured sufficiently to make direct contact with…

General Relativity and Quantum Cosmology · Physics 2017-06-21 Abhay Ashtekar