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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

We review a few topics in Planck-scale physics, with emphasis on possible manifestations in relatively low energy. The selected topics include quantum fluctuations of spacetime, their cumulative effects, uncertainties in energy-momentum…

General Relativity and Quantum Cosmology · Physics 2014-11-17 Y. Jack Ng

We treat two possible phenomenological effects of quantum fluctuations of spacetime geometry: spectral line broadening and angular blurring of the image of a distance source. A geometrical construction will be used to express both effects…

General Relativity and Quantum Cosmology · Physics 2009-11-11 R. T. Thompson , L. H. Ford

We study fluctuations and correlations between spacial regions, generated by the primordial quantum gravitational phase of the universe. We do so by a numerical evaluation of Lorentzian amplitudes in Loop Quantum Gravity, in a…

General Relativity and Quantum Cosmology · Physics 2021-06-17 Francesco Gozzini , Francesca Vidotto

In this paper, we calculate the spectrum of scalar field fluctuations in a bouncing, asymptotically flat Universe, and investigate the dependence of the result on changes in the physics on length scales shorter than the Planck length which…

High Energy Physics - Theory · Physics 2009-11-07 Robert H Brandenberger , Sergio E. Joras , Jerome Martin

Cosmology appears as the most promising way to test and constrain quantum gravity theories. Loop quantum gravity is among the most advanced attempts to perform a non-perturbative quantization of general relativity. Its cosmological…

General Relativity and Quantum Cosmology · Physics 2023-06-27 Killian Martineau

We calculate the power spectrum of vacuum fluctuations of a generic scalar field in a quantum cosmological setting that is manifestly singularity-free. The power spectrum is given in terms of the usual scale invariant spectrum plus scale…

Astrophysics · Physics 2007-05-23 S. Hofmann , O. Winkler

It is proposed that if quantum states of space-time are coherent on null surfaces, holographic Planck-scale fluctuations of inflationary horizons dominate the formation of primordial scalar curvature perturbations. It is shown that the…

Cosmology and Nongalactic Astrophysics · Physics 2020-06-17 Craig Hogan

In papers on primary state diffusion (Percival 1994, 1995), numerical estimates suggested that fluctuations in the space-time metric on the scale of the Planck time (10^-44s) could be detected using atom interferometers. In this paper we…

Quantum Physics · Physics 2009-10-30 Ian C. Percival , Walter T. Strunz

If spacetime undergoes quantum fluctuations, an electromagnetic wavefront will acquire uncertainties in direction as well as phase as it propagates through spacetime. These uncertainties can show up in interferometric observations of…

General Relativity and Quantum Cosmology · Physics 2016-11-15 Y. Jack Ng

The space-time metric is widely believed to be subject to stochastic fluctuations induced by quantum gravity at the Planck scale. This work is based on two different phenomenological approaches being currently made to this topic, and…

Astrophysics · Physics 2009-11-07 R. Le Gallou

We derive the primordial power spectra and spectral indexes of the density fluctuations and gravitational waves in the framework of loop quantum cosmology (LQC) with holonomy and inverse-volume corrections, by using the uniform asymptotic…

General Relativity and Quantum Cosmology · Physics 2015-08-04 Tao Zhu , Anzhong Wang , Gerald Cleaver , Klaus Kirsten , Qin Sheng , Qiang Wu

More recently in [J. Phys. A: Math. Theor. 53, 115303 (2020)], we have introduced a set of noncommutative algebra that describes the space-time at the Planck scale. The interesting significant result we found is that the generalized…

High Energy Physics - Theory · Physics 2021-03-30 Latévi Mohamed Lawson

We set up a covariant renormalisation group equation on a foliated spacetime which preserves background diffeomorphism symmetry. As a first application of the new formalism, we study the effect of quantum fluctuations in Lorentz symmetry…

High Energy Physics - Theory · Physics 2019-03-27 Benjamin Knorr

A phenomenology for the deep spatial geometry of loop quantum gravity is introduced. In the context of a simple model, an atom of space, it is shown how purely combinatorial structures can affect observations. The angle operator is used to…

General Relativity and Quantum Cosmology · Physics 2014-11-21 Seth A. Major

Apart from the assumption that the inflation started at an infinite time in the past, the more realistic initial state of the quantum fluctuations is described by a mixed quantum state imposed at a finite value of the initial time. One of…

General Relativity and Quantum Cosmology · Physics 2023-08-02 S. Cheraghchi , F. Shojai , M. H. Abbassi

We consider a model of modified gravity from the nonperturbative quantization of a metric. We obtain the modified gravitational field equations and the modified conservational equations. We apply it to the FLRW spacetime and find that due…

General Relativity and Quantum Cosmology · Physics 2016-05-20 Rong-Jia Yang

In this work, I review some aspects concerning the evolution of quantum low-energy fields in a foamlike spacetime, with involved topology at the Planck scale but with a smooth metric structure at large length scales, as follows. Quantum…

General Relativity and Quantum Cosmology · Physics 2014-11-17 Luis J. Garay

We study the effects of the trans-Planckian dispersion relation on the spectrum of the primordial density perturbations during inflation. In contrast to the earlier analyses, we do not assume any specific form of the dispersion relation and…

General Relativity and Quantum Cosmology · Physics 2011-07-19 S. Shankaranarayanan

We analyze the size and evolution of quantum fluctuations of cosmologically relevant geometric observables, in the context of the effective relational cosmological dynamics of GFT models of quantum gravity. We consider the fluctuations of…

General Relativity and Quantum Cosmology · Physics 2021-09-23 Luca Marchetti , Daniele Oriti