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We study the role of composite operators in the Asymptotic Safety program for quantum gravity. By including in the effective average action an explicit dependence on new sources we are able to keep track of operators which do not belong to…

General Relativity and Quantum Cosmology · Physics 2017-03-21 Carlo Pagani , Martin Reuter

We analyze the spectral properties of the volume operator of Ashtekar and Lewandowski in Loop Quantum Gravity, which is the quantum analogue of the classical volume expression for regions in three dimensional Riemannian space. Our analysis…

General Relativity and Quantum Cosmology · Physics 2010-11-22 Johannes Brunnemann , David Rideout

The properties of the Volume operator in Loop Quantum Gravity, as constructed by Ashtekar and Lewandowski, are analyzed for the first time at generic vertices of valence greater than four. The present analysis benefits from the general…

General Relativity and Quantum Cosmology · Physics 2010-11-26 Johannes Brunnemann , David Rideout

We review quantum chaos on graphs. We construct a unitary operator which represents the quantum evolution on the graph and study its spectral and wavefunction statistics. This operator is the analogue of the classical evolution operator on…

Chaotic Dynamics · Physics 2007-05-23 Tsampikos Kottos

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

We construct in this article a new realization of quantum geometry, which is obtained by quantizing the recently-introduced flux formulation of loop quantum gravity. In this framework, the vacuum is peaked on flat connections, and states…

General Relativity and Quantum Cosmology · Physics 2021-06-18 Benjamin Bahr , Bianca Dittrich , Marc Geiller

The Hilbert space of loop quantum gravity is usually described in terms of cylindrical functionals of the gauge connection, the electric fluxes acting as non-commuting derivation operators. It has long been believed that this…

High Energy Physics - Theory · Physics 2015-05-18 Aristide Baratin , Bianca Dittrich , Daniele Oriti , Johannes Tambornino

The aim of this article is to provide a rigorous-but-simple steps to prove the hermiticity of the volume operator of Rovelli-Smolin and Ashtekar-Lewandowski using the angular momentum approach, as well as pointing out some subleties which…

General Relativity and Quantum Cosmology · Physics 2021-03-30 S. Ariwahjoedi , I. Husin , I. Sebastian , F. P. Zen

I describe a possible perspective on the current state of loop quantum gravity, at the light of the developments of the last years. I point out that a theory is now available, having a well-defined background-independent kinematics and a…

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

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

The anomalous dimensions of the Planck mass and the cosmological constant are calculated in a renormalizable quantum conformal gravity with a single dimensionless coupling, which is formulated using dimensional regularization on the basis…

High Energy Physics - Theory · Physics 2016-04-11 Ken-ji Hamada , Mikoto Matsuda

We study further the r\^ole of the boundary operator $\O_B$ for macroscopic loop length in the stable definition of 2D quantum gravity provided by the $[{\tilde P},Q]=Q$ formulation. The KdV flows are supplemented by an additional flow with…

High Energy Physics - Theory · Physics 2009-10-22 Clifford V. Johnson , Tim R. Morris , Peter L. White

The equivalence principle, being one of the building blocks of general relativity, seems to be also crucial for analysis of quantum effects in gravity. In this paper we consider the question if the equivalence principle has to hold for…

Quantum Physics · Physics 2023-12-06 Marcin Nowakowski

The velocity circulation, a measure of the rotation of a fluid within a closed path, is a fundamental observable in classical and quantum flows. It is indeed a Lagrangian invariant in inviscid classical fluids. In quantum flows, circulation…

Fluid Dynamics · Physics 2021-03-17 Nicolás P. Müller , Juan Ignacio Polanco , Giorgio Krstulovic

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

We use the mathematical framework of loop quantum gravity (LQG) to study the quantization of three dimensional (Riemannian) gravity with positive cosmological constant (Lambda>0). We show that the usual regularization techniques (successful…

General Relativity and Quantum Cosmology · Physics 2014-11-20 Alejandro Perez , Daniele Pranzetti

Quantum polyhedra constructed from angular momentum operators are the building blocks of space in its quantum description as advocated by Loop Quantum Gravity. Here we extend previous results on the semiclassical properties of quantum…

General Relativity and Quantum Cosmology · Physics 2014-12-31 John Schliemann

We show that the non-Abelian nature of geometric fluxes---the corner-stone in the definition of quantum geometry in the framework of loop quantum gravity (LQG)---follows directly form the continuum canonical commutations relations of…

General Relativity and Quantum Cosmology · Physics 2020-02-03 Alberto S. Cattaneo , Alejandro Perez

We construct the smeared diffeomorphism constraint operator at finite triangulation from the basic holonomy- flux operators of Loop Quantum Gravity, evaluate its continuum limit on the Lewandowski- Marolf habitat and show that the action of…

General Relativity and Quantum Cosmology · Physics 2015-05-28 Alok Laddha , Madhavan Varadarajan

Loop quantum gravity corrections, in the presence of inhomogeneities, can lead to a deformed constraint algebra. Such a deformation implies that the effective theory is no longer generally covariant. As a consequence, the geometrical…

General Relativity and Quantum Cosmology · Physics 2015-06-17 Rakesh Tibrewala