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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

This paper deals with several technical issues of non-perturbative four-dimensional Lorentzian canonical quantum gravity in the continuum that arose in connection with the recently constructed Wheeler-DeWitt quantum constraint operator. 1)…

General Relativity and Quantum Cosmology · Physics 2009-10-30 Thomas Thiemann

In this paper we construct the Hamiltonian constraint operator of loop quantum cosmology using holonomies defined for arbitrary irreducible SU(2) representations labeled by spin J. We show that modifications to the effective semi-classical…

General Relativity and Quantum Cosmology · Physics 2009-11-11 Kevin Vandersloot

An alternative expression for the length operator in loop quantum gravity is presented. The operator is background independent, symmetric, positive semidefinite, and well defined on the kinematical Hilbert space. The expression for the…

General Relativity and Quantum Cosmology · Physics 2010-06-15 Yongge Ma , Chopin Soo , Jinsong Yang

The loop quantum gravity technique is applied to the free bosonic string. A Hilbert space similar to loop space in loop quantum gravity as well as representations of diffeomorphism and hamiltonian constraints on it are constructed. The…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Artem Starodubtsev

A new alternative volume operator is constructed for loop quantum gravity by using the so-called cotriad operators as building blocks. It is shown that the new volume operator shares the same qualitative properties with the standard volume…

General Relativity and Quantum Cosmology · Physics 2016-08-04 Jinsong Yang , Yongge Ma

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

In this second paper on loop quantization of Gowdy model, we introduce the kinematical Hilbert space on which appropriate holonomies and fluxes are well represented. The quantization of the volume operator and the Gauss constraint is…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Kinjal Banerjee , Ghanashyam Date

In loop quantum cosmology, one has to make a choice of SU(2) irreducible representation in which to compute holonomies and regularize the curvature of the connection. The systematic choice made in the literature is to work in the…

General Relativity and Quantum Cosmology · Physics 2017-04-26 Jibril Ben Achour , Suddhasattwa Brahma , Marc Geiller

In this thesis we consider the problem of dynamics in canonical loop quantum gravity, primarily in the context of deparametrized models, in which a scalar field is taken as a physical time variable for the dynamics of the gravitational…

General Relativity and Quantum Cosmology · Physics 2021-01-01 Ilkka Mäkinen

We present quantum holonomy theory, which is a non-perturbative theory of quantum gravity coupled to fermionic degrees of freedom. The theory is based on a C*-algebra that involves holonomy-diffeomorphisms on a 3-dimensional manifold and…

General Relativity and Quantum Cosmology · Physics 2016-11-03 Johannes Aastrup , Jesper M. Grimstrup

The system of gravity coupled to the non-rotational dust field is studied at both classical and quantum levels. The scalar constraint of the system can be written in the form of a true physical Hamiltonian with respect to the dust time. In…

General Relativity and Quantum Cosmology · Physics 2023-11-15 Xiangdong Zhang , Yongge Ma

We show that Vassiliev invariants of knots, appropriately generalized to the spin network context, are loop differentiable in spite of being diffeomorphism invariant. This opens the possibility of defining rigorously the constraints of…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Rodolfo Gambini , Jorge Griego , Jorge Pullin

Although the physical Hamiltonian operator can be constructed in the deparameterized model of loop quantum gravity coupled to a scalar field, its property is still unknown. This open issue is attacked in this paper by considering an…

General Relativity and Quantum Cosmology · Physics 2019-12-17 Cong Zhang , Jerzy Lewandowski , Yongge Ma

We present a quantization of the Hamiltonian and diffeomorphism constraint of canonical quantum gravity in the spin network representation. The novelty consists in considering a space of wavefunctions based on the Vassiliev knot invariants.…

General Relativity and Quantum Cosmology · Physics 2014-11-17 C. Di Bartolo , R. Gambini , J. Griego , J. Pullin

A finite dimensional system with a quadratic Hamiltonian constraint is Dirac quantized in holomorphic, antiholomorphic and mixed representations. A unique inner product is found by imposing Hermitian conjugacy relations on an operator…

General Relativity and Quantum Cosmology · Physics 2010-11-01 Jorma Louko

A covariant spin-foam formulation of quantum gravity has been recently developed, characterized by a kinematics which appears to match well the one of canonical loop quantum gravity. In particular, the geometrical observable giving the area…

General Relativity and Quantum Cosmology · Physics 2014-11-20 You Ding , Carlo Rovelli

Recently, a generally covariant reformulation of 2 dimensional flat spacetime free scalar field theory known as Parameterised Field Theory was quantized using Loop Quantum Gravity (LQG) type `polymer' representations. Physical states were…

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

An alternative quantization of the gravitational Hamiltonian constraint of the $k=-1$ Friedmann-Robertson-Walker model is proposed by treating the Euclidean term and the Lorentzian term independently, mimicking the treatment of full loop…

General Relativity and Quantum Cosmology · Physics 2023-02-23 Jinsong Yang , Cong Zhang , Xiangdong Zhang

We introduce a master constraint operator on the kinematical Hilbert space of loop quantum gravity representing a set of gauge conditions which classically fix the densitized triad to be diagonal. We argue that the master constraint…

General Relativity and Quantum Cosmology · Physics 2024-05-01 Ilkka Mäkinen