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In canonical quantum gravity, when space is a compact manifold with boundary there is a Hamiltonian given by an integral over the boundary. Here we compute the action of this `boundary Hamiltonian' on observables corresponding to open…

General Relativity and Quantum Cosmology · Physics 2009-10-28 John Baez , Javier P. Muniain , Dardo Piriz

The principle of local covariance which was recently introduced admits a generally covariant formulation of quantum field theory. It allows a discussion of structural properties of quantum field theory as well as the perturbative…

High Energy Physics - Theory · Physics 2007-05-23 Klaus Fredenhagen

Canonical quantum gravity provides insights into the quantum dynamics as well as quantum geometry of space-time by its implications for constraints. Loop quantum gravity in particular requires specific corrections due to its quantization…

General Relativity and Quantum Cosmology · Physics 2015-05-14 Martin Bojowald

The first part of this work deals with the development of a natural differential calculus on non-commutative manifolds. The second part extends the covariance and equivalence principle as well studies its kinematical consequences such as…

General Physics · Physics 2008-04-21 Johan Noldus

We study two-dimensional classically integrable field theory with independent boundary condition on each end, and obtain three possible generating functions for integrals of motion when this model is an ultralocal one. Classically…

High Energy Physics - Theory · Physics 2008-11-26 Yi-Xin Chen , Xu-Dong Luo , Ke Wu

An algebraic formulation of general relativity is proposed. The formulation is applicable to quantum gravity and noncommutative space. To investigate quantum gravity we develop the canonical formalism of operator geometry, after…

High Energy Physics - Theory · Physics 2007-05-23 Masaru Siino

The coupling between internal degrees of freedom of quantum systems and their overall motion in an external gravitational field plays a central role in multiple extensions of Einstein's equivalence principle to quantum physics. While…

General Relativity and Quantum Cosmology · Physics 2026-03-04 Thomas B. Mieling

We study the boundary terms of the spectral action of the noncommutative space, defined by the spectral triple dictated by the physical spectrum of the standard model, unifying gravity with all other fundamental interactions. We prove that…

High Energy Physics - Theory · Physics 2008-11-26 Ali H. Chamseddine , Alain Connes

In this paper, we will make an attempt to clarify the relation between three-dimensional euclidean loop quantum gravity with vanishing cosmological constant and quantum field theory in the continuum. We will argue, in particular, that in…

General Relativity and Quantum Cosmology · Physics 2018-10-22 Wolfgang Wieland

The past few years have seen a revived interest in quantum geometrical characterizations of band structures due to the rapid development of topological insulators and semi-metals. Although the metric tensor has been connected to many…

Mesoscale and Nanoscale Physics · Physics 2023-03-07 Adrien Bouhon , Abigail Timmel , Robert-Jan Slager

We argue that a consistent coupling of a quantum theory to gravity requires an extension of ordinary `first order' Riemannian geometry to second order Riemannian geometry, which incorporates both a line element and an area element. This…

High Energy Physics - Theory · Physics 2025-04-11 Folkert Kuipers

In the one-loop approximation for Euclidean quantum gravity, the boundary conditions which are completely invariant under gauge transformations of metric perturbations involve both normal and tangential derivatives of the metric…

General Relativity and Quantum Cosmology · Physics 2022-04-13 Giampiero Esposito

On the path towards quantum gravity, we find friction between temporal relations in quantum mechanics (QM) (where they are fixed and field-independent), and in general relativity (where they are field-dependent and dynamic). This paper aims…

General Relativity and Quantum Cosmology · Physics 2017-11-28 Henrique Gomes

We review applications of noncommutative geometry in canonical quantum gravity. First, we show that the framework of loop quantum gravity includes natural noncommutative structures which have, hitherto, not been explored. Next, we present…

General Relativity and Quantum Cosmology · Physics 2012-03-29 Johannes Aastrup , Jesper M. Grimstrup

The infinite dimensional generalization of the quantum mechanics of extended objects, namely, the quantum field theory of extended objects is employed to address the hitherto nonrenormalizable gravitational interaction following which the…

High Energy Physics - Theory · Physics 2009-09-25 Ramchander R. Sastry

Quantum gravity was born as that branch of modern theoretical physics that tries to unify its guiding principles, i.e., quantum mechanics and general relativity. Nowadays it is providing new insight into the unification of all fundamental…

High Energy Physics - Theory · Physics 2011-08-17 Giampiero Esposito

A crucial problem in quantum cosmology is a careful analysis of the one-loop semiclassical approximation for the wave function of the universe, after an appropriate choice of mixed boundary conditions. The results for Euclidean quantum…

High Energy Physics - Theory · Physics 2007-05-23 Giampiero Esposito , Alexander Yu. Kamenshchik

The present paper is the companion of [1] in which we proposed a scheme that tries to derive the Quantum Field Theory (QFT) on Curved Spacetimes (CST) limit from background independent Quantum General Relativity (QGR). The constructions of…

General Relativity and Quantum Cosmology · Physics 2014-11-17 Hanno Sahlmann , Thomas Thiemann

Following the same steps made for a scalar field in a parallel publication, we propose a class of perturbative theories of quantum gravity based on fractional operators, where the kinetic operator of the graviton is either made of…

General Relativity and Quantum Cosmology · Physics 2021-08-16 Gianluca Calcagni

The space of states and operators for a large class of background independent theories of quantum spacetime dynamics is defined. The SU(2) spin networks of quantum general relativity are replaced by labelled compact two-dimensional…

General Relativity and Quantum Cosmology · Physics 2016-08-25 Fotini Markopoulou , Lee Smolin