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Loop quantum gravity is a mature theory. To proceed to explicit calculations in cosmology, it is necessary to make assumptions and simplifications based on the symmetries of the cosmological setting. Symmetry reduction is especially…

General Relativity and Quantum Cosmology · Physics 2016-08-03 Aurélien Barrau , Boris Bolliet

Loop quantum cosmology is an application of recent developments for a non-perturbative and background independent quantization of gravity to a cosmological setting. Characteristic properties of the quantization such as discreteness of…

Astrophysics · Physics 2009-11-13 Martin Bojowald

A manifestly Lorentz-covariant formulation of Loop Quantum Gravity (LQG) is given in terms of finite-dimensional representations of the Lorentz group. The formulation accounts for discrete symmetries, such as parity and time-reversal, and…

General Relativity and Quantum Cosmology · Physics 2021-12-08 Francesco Cianfrani

We study perturbative noncommutative quantum gravity by expanding the gravitational field about a fixed classical background. A calculation of the one loop gravitational self-energy graph reveals that only the non-planar graviton loops are…

High Energy Physics - Theory · Physics 2009-10-31 J. W. Moffat

We propose a new representation for gauge theories and quantum gravity. It can be viewed as a generalization of the loop representation. We make use of a recently introduced extension of the group of loops into a Lie Group. This extension…

General Relativity and Quantum Cosmology · Physics 2009-10-22 C. Di Bartolo , R. Gambini , J. Griego , J. Pullin

We adopt the point of view that (Riemannian) classical and (loop-based) quantum descriptions of geometry are macro- and micro-descriptions in the usual statistical mechanical sense. This gives rise to the notion of geometrical entropy,…

General Relativity and Quantum Cosmology · Physics 2009-10-28 Kirill V. Krasnov

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

Vielbeins are necessary when coupling General Relativity (GR) to fermionic matter. This enhances the gauge group of GR to include local Lorentz transformations. In view of a reduced phase space formulation of quantum gravity, in this work…

General Relativity and Quantum Cosmology · Physics 2023-05-12 Thomas Thiemann

..."but we do not have quantum gravity." This phrase is often used when analysis of a physical problem enters the regime in which quantum gravity effects should be taken into account. In fact, there are several models of the gravitational…

General Relativity and Quantum Cosmology · Physics 2010-12-23 Marcin Domagala , Kristina Giesel , Wojciech Kaminski , Jerzy Lewandowski

The kinematical setting of spherically symmetric quantum geometry, derived from the full theory of loop quantum gravity, is developed. This extends previous studies of homogeneous models to inhomogeneous ones where interesting field theory…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Martin Bojowald

The vacuum is the lowest energy state of a field in a certain region of space. This definition implies that no particles can be present in the vacuum state. In classical physics, the only features of vacuum are those of its geometry. For…

Quantum Physics · Physics 2015-12-15 G. S. Paraoanu

We introduce squeezed vacua in loop quantum gravity, a new overcomplete basis of states that contain prescribable correlations between geometric operators. We study the behavior of long-range correlations and discuss the relevance of these…

General Relativity and Quantum Cosmology · Physics 2016-05-19 Eugenio Bianchi , Jonathan Guglielmon , Lucas Hackl , Nelson Yokomizo

The nature and properties of the vacuum as well as the meaning and localization properties of one or many particle states have attracted a fair amount of attention and stirred up sometimes heated debate in relativistic quantum field theory…

Mathematical Physics · Physics 2007-05-23 S. De Bievre

We suggest that in a recently proposed framework for quantum gravity, where Vassiliev invariants span the the space of states, the latter is dramatically reduced if one has a non-vanishing cosmological constant. This naturally suggests that…

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

We study the noncommutative geometrical structures of quantum entangled states. We show that the space of a pure entangled state is a noncommutative space. In particular we show that by rewritten the conifold or the Segre variety we can get…

Quantum Physics · Physics 2015-05-19 Hoshang Heydari

Covariant generalizations of well-known wave equations predict the existence of inertial-gravitational effects for a variety of quantum systems that range from Bose-Einstein condensates to particles in accelerators. Additional effects arise…

General Relativity and Quantum Cosmology · Physics 2007-05-23 G. Papini

Quantum tunneling introduces a fundamental difference between classical and quantum mechanics. Whenever the classical ground state is non-unique (degenerate), quantum mechanics restore uniqueness thanks to tunneling. A condensate in a…

Quantum Physics · Physics 2012-09-10 Qiang Du , Martine Le Berre , Yves Pomeau

In the last decade, progress on quantization of homogeneous cosmological spacetimes using techniques of loop quantum gravity has led to insights on various fundamental questions and has opened new avenues to explore Planck scale physics.…

General Relativity and Quantum Cosmology · Physics 2016-12-06 Ivan Agullo , Parampreet Singh

Loop Quantum Gravity defines the quantum states of space geometry as spin networks and describes their evolution in time. We reformulate spin networks in terms of harmonic oscillators and show how the holographic degrees of freedom of the…

General Relativity and Quantum Cosmology · Physics 2009-11-11 Florian Girelli , Etera R. Livine

Standard quantum mechanics and gravity are used to estimate the mass and size of idealized gravitating systems where position states of matter and geometry become indeterminate. It is proposed that well-known inconsistencies of standard…

General Relativity and Quantum Cosmology · Physics 2014-12-05 Craig J. Hogan