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This introductory review is addressed to beginning researchers. Some of the distinguishing features of loop quantum gravity are illustrated through loop quantum cosmology of FRW models. In particular, these examples illustrate: i) how…

General Relativity and Quantum Cosmology · Physics 2010-11-11 Abhay Ashtekar

A new framework of loop quantization that assimilates conformal and scale invariance is constructed and is found to be applicable to a large class of physically important theories of gravity and gravity-matter systems. They include general…

General Relativity and Quantum Cosmology · Physics 2019-01-02 Charles H. -T. Wang , Daniel P. F. Rodrigues

The question of a possibility of opening a wormhole due to the deformation of the equation of state of the matter caused by quantum gravity effects is considered. As a wormhole environment, the previously considered model of a galaxy with…

General Physics · Physics 2021-02-23 Igor Nikitin

We investigate a possible unified theory of all interactions which is based only on fundamental spinor fields. The vielbein and metric arise as composite objects. The effective quantum gravitational theory can lead to a modification of…

High Energy Physics - Theory · Physics 2009-11-10 C. Wetterich

Loop quantum gravity in its Hamiltonian form relies on a connection formulation of the gravitational phase space with three key properties: 1.) a compact gauge group, 2.) real variables, and 3.) canonical Poisson brackets. In conjunction,…

General Relativity and Quantum Cosmology · Physics 2024-12-09 Norbert Bodendorfer , Konstantin Eder , Xiangdong Zhang

A possible astrophysical object to be found in General Relativity is the wormhole. This special solution describes a topological bridge connecting points in two distinguished universes or two different points in the same universe. Despite…

General Relativity and Quantum Cosmology · Physics 2023-06-21 Moreshwar Tayde , Joao R. L. Santos , Julia N. Araujo , P. K. Sahoo

We apply duality rotations and complex transformations to the Schwarzschild metric to obtain wormhole geometries with two asymptotically flat regions connected by a throat. In the simplest case these are the well-known wormholes supported…

High Energy Physics - Theory · Physics 2016-08-03 Gary W. Gibbons , Mikhail S. Volkov

Noncommutative geometry, an offshoot of string theory, replaces point-like particles by smeared objects. These local effects have led to wormhole solutions in a semiclassical setting, but it has also been claimed that the noncommutative…

General Relativity and Quantum Cosmology · Physics 2024-12-24 Peter K. F. Kuhfittig

Vacuum spherically symmetric loop quantum gravity in the midi-superspace approximation using inhomogeneous horizon-penetrating slices has been studied for a decade, and it has been noted that the singularity is eliminated. It is replaced by…

General Relativity and Quantum Cosmology · Physics 2024-02-20 Rodolfo Gambini , Javier Olmedo , Jorge Pullin

The canonical ``loop'' formulation of quantum gravity is a mathematically well defined, background independent, non perturbative standard quantization of Einstein's theory of General Relativity. Some among the most meaningful results of the…

General Relativity and Quantum Cosmology · Physics 2012-06-12 R. De Pietri

Effective topological field theories describe the properties of Dirac fermions in the low-energy regime. In this work, we introduce a new emergent gravity model by considering Dirac fermions invariant under local de Sitter transformations…

General Relativity and Quantum Cosmology · Physics 2016-01-19 Giandomenico Palumbo

We continue our investigation of an improved quantization scheme for spherically symmetric loop quantum gravity. We find that in the region where the black hole singularity appears in the classical theory, the quantum theory contains…

General Relativity and Quantum Cosmology · Physics 2021-06-16 Rodolfo Gambini , Javier Olmedo , Jorge Pullin

We discuss some arguments in favour of the proposal that the quantum correlations contained in the pure state-vector evolving according to Schoedinger equation can be eliminated by the action of multiply connected wormholes during…

Quantum Physics · Physics 2011-04-15 Pedro F. Gonzalez-Diaz

Four-dimensional gravity admits many equivalent formulations - metric, Einstein-Cartan, teleparallel, McDowell-Mansouri, among others - each offering distinct advantages, particularly, in view of quantization. We propose a new formulation…

General Relativity and Quantum Cosmology · Physics 2026-03-13 Maïté Dupuis , Florian Girelli , Oleksandra Hrytseniak , Wolfgang Wieland

Much attention has been recently devoted to modified theories of gravity in the attempt to efficiently describe both early inflation and late-time acceleration of our universe without referring to the cosmological constant or other ad hoc…

General Relativity and Quantum Cosmology · Physics 2015-06-16 R. Di Criscienzo , R. Myrzakulov , L. Sebastiani

In this work we show the existence of traversable wormhole and time-machine solutions in a modified theory of gravity where matter and curvature are nonminimally coupled. Those solutions present a nontrivial redshift function and exist even…

High Energy Physics - Theory · Physics 2013-10-24 Orfeu Bertolami , Ricardo Zambujal Ferreira

In a recent paper [1], it was introduced a new class of gravitational theories with two local degrees of freedom. The existence of these theories apparently challenges the distinctive role of general relativity as the unique non-linear…

General Relativity and Quantum Cosmology · Physics 2018-10-30 Raúl Carballo-Rubio , Francesco Di Filippo , Stefano Liberati

Static and spherically symmetric wormhole solutions can be reconstructed in the framework of curvature based Extended Theories of Gravity. In particular, extensions of the General Relativity, in metric and curvature formalism give rise to…

General Relativity and Quantum Cosmology · Physics 2021-02-23 Vittorio De Falco , Emmanuele Battista , Salvatore Capozziello , Mariafelicia De Laurentis

Group field theories represent a 2nd quantized reformulation of the loop quantum gravity state space and a completion of the spin foam formalism. States of the canonical theory, in the traditional continuum setting, have support on graphs…

General Relativity and Quantum Cosmology · Physics 2015-02-17 Daniele Oriti , James P. Ryan , Johannes Thürigen

We propose a simple model of entanglement generated by geometry, studying non-relativistic massive L\'evy-Leblond fermions in the $1+2$ geometry of a Bronnikov-Ellis wormhole. The model is equivalent to that of relativistic massless Dirac…

General Relativity and Quantum Cosmology · Physics 2018-06-28 M. Cariglia , G. W. Gibbons