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Quantum gravity is known to be mostly a kind of metaphysical speculation. In this brief essay, we try to argue that, although still extremely difficult to reach, observational signatures can in fact be expected. The early universe is an…

General Relativity and Quantum Cosmology · Physics 2012-06-07 Aurelien Barrau , Julien Grain

We consider observational consequences of the entanglement between our universe and a hypothetical twin anti-universe in the third quantization scheme of the canonical quantum gravity. Based on our previous investigations we select some…

General Relativity and Quantum Cosmology · Physics 2022-11-08 Samuel Barroso Bellido , Mariusz P. Dabrowski

In this article we review the foundations and the present status of loop quantum gravity. It is short and relatively non-technical, the emphasis is on the ideas, and the flavor of the techniques. In particular, we describe the kinematical…

General Relativity and Quantum Cosmology · Physics 2011-02-02 Hanno Sahlmann

We investigate the potential of using cosmic voids as a probe to constrain cosmological parameters through the gravitational lensing effect of the cosmic microwave background (CMB) and make predictions for the next generation surveys. By…

Cosmology and Nongalactic Astrophysics · Physics 2016-02-19 Teeraparb Chantavat , Utane Sawangwit , P. M. Sutter , Benjamin D. Wandelt

Observations of the Cosmic Microwave Background (CMB) are discussed, with particular emphasis on current ground-based experiments and on future satellite, balloon and interferometer experiments. Observational techniques and the effects of…

Astrophysics · Physics 2009-10-31 A. N. Lasenby , A. W. Jones , Y. Dabrowski

We explore the extension of quantum cosmology outside the homogeneous approximation, using the formalism of loop quantum gravity. We introduce a model where some of the inhomogeneous degrees of freedom are present, providing a tool for…

General Relativity and Quantum Cosmology · Physics 2008-12-18 Carlo Rovelli , Francesca Vidotto

A novel primordial spectrum with a dynamical scale of quantum gravity origin is proposed to explain the sharp fall off of the angular power spectra at low multipoles in the COBE and WMAP observations. The spectrum is derived from quantum…

Astrophysics · Physics 2009-11-10 Ken-ji Hamada , Tetsuyuki Yukawa

General Relativity is an extremely successful theory, at least for weak gravitational fields, however, it breaks down at very high energies, such as in correspondence of the initial singularity. Quantum Gravity is expected to provide more…

General Relativity and Quantum Cosmology · Physics 2023-04-20 Ana Rita Ribeiro , Daniele Vernieri , Francisco S. N. Lobo

The goal of this article is to provide an overview of the current state of the art in loop quantum cosmology for three sets of audiences: young researchers interested in entering this area; the quantum gravity community in general; and,…

General Relativity and Quantum Cosmology · Physics 2011-09-23 Abhay Ashtekar , Parampreet Singh

The appearance of the big bounce (BB) in the evolution of the universe is analyzed in the setting of loop quantum cosmology (LQC). Making use of an idea of a minimum length turns classical Big Bang into BB. We argue why the spectrum of the…

General Relativity and Quantum Cosmology · Physics 2015-03-13 Piotr Dzierzak , Jacek Jezierski , Przemyslaw Malkiewicz , Wlodzimierz Piechocki

Following the recent measurement of the acoustic peak by the BOOMERanG and MAXIMA experiments in the CMB anisotropy angular power spectrum, many analyses have found that the geometry of the Universe is very close to flat, but slightly…

Astrophysics · Physics 2009-10-31 Alessandro Melchiorri , Louise M. Griffiths

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

We study the effects of modifications of gravity after Big Bang Nucleosynthesis (BBN) which would manifest themselves mainly before recombination. We consider their effects on the Cosmic Microwave Background (CMB) radiation and on the…

Cosmology and Nongalactic Astrophysics · Physics 2014-06-18 Philippe Brax , Carsten van de Bruck , Sebastien Clesse , Anne-Christine Davis , Gregory Sculthorpe

This study investigates quantum gravity effects within the framework of an effective loop quantum gravity (LQG) black hole model parameterized by $\zeta$, utilizing precision measurements from solar system experiments and astrophysical…

General Relativity and Quantum Cosmology · Physics 2025-07-28 Wen-Juan Ai , Ruo-Ting Chen , Li-Gang Zhu , Jian-Pin Wu

There have been vigorous research attempts to test various modified gravity theories by usingphysics of the cosmic microwave background (CMB). Meanwhile, symmetry breaking such as Higgsmechanism is one of the most important phenomena in…

General Relativity and Quantum Cosmology · Physics 2020-07-01 Jiwon Park , Tae Hoon Lee

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 Cosmic Microwave Background (CMB) radiation lensing is a promising tool to study the physics of early universe. In this work we probe the imprints of deviations from isotropy and scale invariance of primordial curvature perturbation…

Cosmology and Nongalactic Astrophysics · Physics 2016-06-01 Farbod Hassani , Shant Baghram , Hassan Firouzjahi

The Cosmic Microwave Background (CMB) provides a precious window on fundamental physics at very high energy scales, possibly including quantum gravity, GUTs and supersymmetry. The CMB has already enabled defect-based rivals to inflation to…

Astrophysics · Physics 2009-09-11 John Ellis

Loop Quantum Gravity is a formalism for describing the quantum mechanics of the gravitational field based on the canonical quantization of General Relativity. The most important result of LQG is that geometric quantities such as area and…

General Relativity and Quantum Cosmology · Physics 2019-10-25 W. F. Chagas-Filho

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