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In Loop Quantum Gravity mathematically rigorous models of full quantum gravity were proposed. In this paper we study a cosmological sector of one of the models describing quantum gravity with positive cosmological constant coupled to…

General Relativity and Quantum Cosmology · Physics 2022-11-09 Marcin Kisielowski

Loop quantum gravity introduces strong non-perturbative modifications to the dynamical equations in the semi-classical regime, which are responsible for various novel effects, including resolution of the classical singularity in a Friedman…

High Energy Physics - Theory · Physics 2007-05-23 Martin Bojowald , Roy Maartens , Parampreet Singh

Loop quantum cosmology homogeneous models with a massless scalar field show that the big-bang singularity can be replaced by a big quantum bounce. To gain further insight on the nature of this bounce, we study the semi-discrete loop quantum…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Pablo Laguna

Aspects of the full theory of loop quantum gravity can be studied in a simpler context by reducing to symmetric models like cosmological ones. This leads to several applications where loop effects play a significant role when one is…

General Relativity and Quantum Cosmology · Physics 2014-11-17 Martin Bojowald

The macroscopic effects of the quantum conformal anomaly are evaluated in a simplified two-dimensional model of gravitational collapse. The effective action and stress tensor of the anomaly can be expressed in a local quadratic form by the…

General Relativity and Quantum Cosmology · Physics 2023-09-08 Emil Mottola , Mani Chandra , Gian Mario Manca , Evgeny Sorkin

A gravitationally collapsed object can bounce-out from its horizon via a tunnelling process that violates the classical equations in a finite region. Since tunnelling is a non-perturbative phenomenon, it cannot be described in terms of…

General Relativity and Quantum Cosmology · Physics 2016-10-26 Marios Christodoulou , Carlo Rovelli , Simone Speziale , Ilya Vilensky

A set of diverse but mutually consistent results obtained in different settings has spawned a new view of loop quantum gravity and its physical implications, based on the interplay of operator calculations and effective theory: Quantum…

General Relativity and Quantum Cosmology · Physics 2012-12-27 Martin Bojowald

The structure of the Cauchy Horizon singularity of a black hole formed in a generic collapse is studied by means of a renormalization group equation for quantum gravity. It is shown that during the early evolution of the Cauchy Horizon the…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Alfio Bonanno , Martin Reuter

This study explores the gravitational collapse of a massless scalar field within Quadratic Gravity treated as a dimension-four operator Effective Field Theory extension to General Relativity. The additional degrees of freedom associated…

General Relativity and Quantum Cosmology · Physics 2025-05-08 Ramiro Cayuso

Critical gravitational collapse offers a unique window into regimes of arbitrarily high curvature, culminating in a naked singularity arising from smooth initial data -- thus providing a dynamical counterexample to weak cosmic censorship.…

General Relativity and Quantum Cosmology · Physics 2026-05-18 Marija Tomašević , Chih-Hung Wu

Several examples are known where quantum gravity effects resolve the classical big bang singularity by a bounce. The most detailed analysis has probably occurred for loop quantum cosmology of isotropic models sourced by a free, massless…

General Relativity and Quantum Cosmology · Physics 2008-12-18 Martin Bojowald

We study how the presence of an area gap, different than zero, affects the gravitational collapse of a dust ball. The implementation of such discreteness is achieved through the framework of polymer quantization, a scheme inspired by loop…

General Relativity and Quantum Cosmology · Physics 2025-05-13 L. Boldorini , G. Montani

It is well known that a closed universe with a minimally coupled massive scalar field always collapses to a singularity unless the initial conditions are extremely fine tuned. We show that the corrections to the equations of motion for the…

General Relativity and Quantum Cosmology · Physics 2009-11-10 Parampreet Singh , Alexey Toporensky

In recent years, Loop Quantum Gravity has emerged as a solid candidate for a nonperturbative quantum theory of General Relativity. It is a background independent theory based on a description of the gravitational field in terms of…

General Relativity and Quantum Cosmology · Physics 2009-10-16 Guillermo A. Mena Marugan

We present a new formalism for numerically treating the semiclassical gravitational collapse of a scalar quantum field in the radially symmetric case. Our formalism is time reversal invariant and the evolution of the scalar fields is…

General Relativity and Quantum Cosmology · Physics 2021-12-01 Jana N. Guenther , Christian Hoelbling , Lukas Varnhorst

Loop quantum cosmology predicts that quantum gravity effects resolve the big-bang singularity and replace it by a cosmic bounce. Furthermore, loop quantum cosmology can also modify the form of primordial cosmological perturbations, for…

General Relativity and Quantum Cosmology · Physics 2017-06-28 Edward Wilson-Ewing

In an attempt to re-establish space-time as an essential frame for formulating quantum gravity - rather than an "emergent" one -, we find that exact invariance under scale transformations is an essential new ingredient for such a theory.…

General Relativity and Quantum Cosmology · Physics 2009-09-21 Gerard 't Hooft

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

General relativity successfully describes space-times at scales that we can observe and probe today, but it cannot be complete as a consequence of singularity theorems. For a long time there have been indications that quantum gravity will…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Martin Bojowald

Black Holes have always played a central role in investigations of quantum gravity. This includes both conceptual issues such as the role of classical singularities and information loss, and technical ones to probe the consistency of…

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