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Emergent modified gravity presents a new set of generally covariant gravitational theories in which the space-time metric is not directly given by one of the fundamental fields. A metric compatible with the modified dynamics of gravity is…

General Relativity and Quantum Cosmology · Physics 2024-04-09 Martin Bojowald , Erick I. Duque

We study the role of the Barbero-Immirzi parameter $\gamma$ and the choice of connection in the construction of (a symmetry-reduced version of) loop quantum gravity. We start with the four-dimensional Lorentzian Holst action that we reduce…

General Relativity and Quantum Cosmology · Physics 2015-05-19 Jibril Ben Achour , Marc Geiller , Karim Noui , Chao Yu

We give a survey of our joint ongoing work with Ali Chamseddine, Slava Mukhanov and Walter van Suijlekom. We show how a problem purely motivated by "how geometry emerges from the quantum formalism" gives rise to a slightly noncommutative…

High Energy Physics - Theory · Physics 2017-03-14 Alain Connes

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

We consider non minimal coupling between matters and gravity in modified theories of gravity. In contrary to the current common sense, we report that quantum mechanics can effectively emerge when the space-time geometry is sufficiently…

General Relativity and Quantum Cosmology · Physics 2008-11-27 Qasem Exirifard

Polymer quantum mechanics has been studied as a simplified picture that reflects some of the key properties of Loop Quantum Gravity; however, while the fate of relativistic symmetries in Loop Quantum Gravity is still not established, it is…

General Relativity and Quantum Cosmology · Physics 2017-12-06 Giovanni Amelino-Camelia , Michele Arzano , Malú Maira Da Silva , Daniel H. Orozco-Borunda

In this chapter we take up the quantum Riemannian geometry of a spatial slice of spacetime. While researchers are still facing the challenge of observing quantum gravity, there is a geometrical core to loop quantum gravity that does much to…

General Relativity and Quantum Cosmology · Physics 2023-02-07 Hal M. Haggard , Jerzy Lewandowski , Hanno Sahlmann

Quantum systems are viewed as emergent systems from the fundamental degrees of freedom. The laws and rules of quantum mechanics are understood as an effective description, valid for the emergent systems and specially useful to handle…

Mathematical Physics · Physics 2025-11-26 Ricardo Gallego Torromé

Starting from an action for discretized gravity we derive a canonical formalism that exactly reproduces the dynamics and (broken) symmetries of the covariant formalism. For linearized Regge calculus on a flat background -- which exhibits…

General Relativity and Quantum Cosmology · Physics 2011-08-11 Bianca Dittrich , Philipp A Hoehn

Emergence of classicality from quantum mechanics, a hotly debated topic, has had no satisfactory resolution so far. Various approaches including decoherence and gravitational interactions have been suggested. In the present work, the…

Quantum Physics · Physics 2023-02-08 Sourav Kesharee Sahoo , Radhika Vathsan , Tabish Qureshi

In order to study 3d loop quantum gravity coupled to matter, we consider a simplified model of abelian quantum gravity, the so-called U(1)^3 model. Abelian gravity coupled to a scalar field shares a lot of commonalities with parameterized…

General Relativity and Quantum Cosmology · Physics 2019-05-01 Christoph Charles

Assuming that Quantum Mechanics is universal and that it can be applied over all scales, then the Universe is allowed to be in a quantum superposition of states, where each of them can correspond to a different space-time geometry. How can…

General Relativity and Quantum Cosmology · Physics 2024-02-27 José Luis Gaona-Reyes , Lucía Menéndez-Pidal , Mir Faizal , Matteo Carlesso

Fully covariant wave equations predict the existence of a class of inertial-gravitational effects that can be tested experimentally. In these equations inertia and gravity appear as external classical fields, but, by conforming to general…

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

The Barbero-Immirzi parameter is a one parameter quantization ambiguity underpinning the loop approach to quantum gravity that bears tantalizing similarities to the theta parameter of gauge theories such as Yang-Mills and QCD. Despite the…

High Energy Physics - Theory · Physics 2011-01-17 Simone Mercuri , Andrew Randono

In loop quantum gravity, states of the gravitational field turn out to be excitations over a vacuum state that is sharply peaked on a degenerate spatial geometry. While this vacuum is singled out as fundamental due to its invariance…

General Relativity and Quantum Cosmology · Physics 2012-05-15 Tim Koslowski , Hanno Sahlmann

Certain versions of mimetic gravity have recently been claimed to present potential covariant theories of canonically modified spherically symmetric gravity, motivated by ingredients from loop quantum gravity. If such an equivalence were to…

General Relativity and Quantum Cosmology · Physics 2024-04-22 Martin Bojowald , Erick I. Duque

In this work, we have studied classical and quantum systems in interaction by means of geometric reduction procedure. The main target is the description in these terms of fundamental interactions. We have shown that, to describe in a…

Mathematical Physics · Physics 2017-03-22 M. Laudato

Quantum groups and non-commutative spaces have been repeatedly utilized in approaches to quantum gravity. They provide a mathematically elegant cut-off, often interpreted as related to the Planck-scale quantum uncertainty in position. We…

General Relativity and Quantum Cosmology · Physics 2011-08-09 Eugenio Bianchi , Carlo Rovelli

We consider a classical spinning particle in the frame of the relativistic physics by means of a covariant Hamiltonian and of a generalization of Poisson brackets which take into account the gauge fields. We obtain different equations of…

High Energy Physics - Theory · Physics 2007-05-23 A. Berard , J. Lages , H. Mohrbach

A detailed study is made of the noncommutative geometry of $R^3_q$, the quantum space covariant under the quantum group $SO_q(3)$. For each of its two $SO_q(3)$-covariant differential calculi we find its metric, the corresponding frame and…

Quantum Algebra · Mathematics 2012-09-28 Gaetano Fiore , John Madore