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This work addresses a specific technical question of relevance to canonical quantization of gravity using the so-called new variables and loop-based techniques of Ashtekar, Rovelli, and Smolin. In particular, certain `superselection laws'…

General Relativity and Quantum Cosmology · Physics 2009-10-30 Donald Marolf , José Mourão , Thomas Thiemann

The operator algebraic framework plays an important role in mathematical physics. Many different operator algebras exist for example for a theory of quantum mechanics. In Loop Quantum Gravity only two algebras have been introduced until…

General Relativity and Quantum Cosmology · Physics 2011-08-24 Diana Kaminski

In this article we review the foundations and the present status of loop quantum gravity. It is short and relatively non-technical, the emphasis is on the ideas, and the flavor of the techniques. In particular, we describe the kinematical…

General Relativity and Quantum Cosmology · Physics 2011-02-02 Hanno Sahlmann

Spherically symmetric models of loop quantum gravity have been studied recently by different methods that aim to deal with structure functions in the usual constraint algebra of gravitational systems. As noticed by Gambini and Pullin, a…

General Relativity and Quantum Cosmology · Physics 2015-09-09 Martin Bojowald , Suddhasattwa Brahma , Juan D. Reyes

The Hamiltonian formulation of the lowest-order projectable Horava gravity, namely the so-called $\lambda$-$R$ gravity, is studied. Since a preferred foliation has been chosen in projectable Horava gravity, there is no local Hamiltonian…

General Relativity and Quantum Cosmology · Physics 2021-01-01 Xiangdong Zhang , Jinsong Yang , Yongge Ma

In this review, the fundamental structure of loop quantum gravity is presented pedagogically. Our main aim is to help non-experts to understand the motivations, basic structures, as well as general results. It may also be beneficial to…

General Relativity and Quantum Cosmology · Physics 2011-05-16 Muxin Han , Weiming Huang , Yongge Ma

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

There is a precise sense in which the requirement of background independence suffices to uniquely select the kinematics of loop quantum gravity (LQG). Specifically, the fundamental kinematic algebra of LQG admits a unique diffeomorphism…

General Relativity and Quantum Cosmology · Physics 2010-03-12 Abhay Ashtekar

The holonomy-flux algebra $\A$ of loop quantum gravity is known to admit a natural representation that is uniquely singled out by the requirement of covariance under spatial diffeomorphisms. In the cosmological context, the requirement of…

General Relativity and Quantum Cosmology · Physics 2015-06-11 Abhay Ashtekar , Miguel Campiglia

In this paper, an attempt is made to represent 5+1 dimensional gravity (via ADM formalism) in terms of the loop constructions introduced by the author in a companion paper. The "momenta" and "velocity" from the earlier paper, which were…

General Relativity and Quantum Cosmology · Physics 2013-05-28 Madhavan Venkatesh

We consider a k=0 Friedman-Robertson-Walker (FRW) model within loop quantum cosmology (LQC) and explore the issue of its semiclassical limit. The model is exactly solvable and allows us to construct analytical (Gaussian) coherent-state…

General Relativity and Quantum Cosmology · Physics 2012-10-08 Alejandro Corichi , Edison Montoya

As modified gravity theories, the 4-dimensional metric $f(R)$ theories are cast into connection dynamical formalism with real $su(2)$-connections as configuration variables. This formalism enables us to extend the non-perturbative loop…

General Relativity and Quantum Cosmology · Physics 2015-05-28 Xiangdong Zhang , Yongge Ma

We propose a quantum symmetry reduction of loop quantum gravity to Bianchi I spacetimes. To this end, we choose the diagonal metric gauge for the spatial diffeomorphism constraint at the classical level, leading to an…

General Relativity and Quantum Cosmology · Physics 2015-04-16 Norbert Bodendorfer

This work introduces a new space $\T'_*$ of `vertex-smooth' states for use in the loop approach to quantum gravity. Such states provide a natural domain for Euclidean Hamiltonian constraint operators of the type introduced by Thiemann (and…

General Relativity and Quantum Cosmology · Physics 2015-06-25 Jerzy Lewandowski , Donald Marolf

The continuum limit of loop quantum gravity is still an open problem. Indeed, no proper dynamics in known to start with and we still lack the mathematical tools to study its would-be continuum limit. In the present PhD dissertation, we will…

General Relativity and Quantum Cosmology · Physics 2017-06-01 Christoph Charles

The kinematics of loop gravity can be given a manifestly Lorentz-covariant formulation: the conventional SU(2)-spin-network Hilbert space can be mapped to a space K of SL(2,C) functions, where Lorentz covariance is manifest. K can be…

General Relativity and Quantum Cosmology · Physics 2011-05-25 Carlo Rovelli , Simone Speziale

Quantum holonomy theory is a candidate for a non-perturbative theory of quantum gravity coupled to fermions. The theory is based on the QHD(M) algebra, which essentially encodes how matter degrees of freedom are moved on a three-dimensional…

General Relativity and Quantum Cosmology · Physics 2016-10-19 Johannes Aastrup , Jesper M. Grimstrup

In this work, we study the classical and quantum properties of the unique commutative Lorentz-covariant connection for loop quantum gravity. This connection has been found after solving the second-class constraints inherited from the…

General Relativity and Quantum Cosmology · Physics 2011-08-12 Marc Geiller , Marc Lachieze-Rey , Karim Noui

In the framework of loop quantum cosmology anomaly free quantizations of the Hamiltonian constraint for Bianchi class A, locally rotationally symmetric and isotropic models are given. Basic ideas of the construction in (non-symmetric) loop…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Martin Bojowald

Important characteristics of the loop approach to quantum gravity are a specific choice of the algebra A of observables and of a representation of A on a measure space over the space of generalized connections. This representation is…

General Relativity and Quantum Cosmology · Physics 2011-01-27 Hanno Sahlmann