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Loop quantum cosmology provides an efficient framework to study the evolution of the Universe beyond the classical Big Bang paradigm. Because of holonomy corrections, the singularity is replaced by a "bounce". The dynamics of the background…

General Relativity and Quantum Cosmology · Physics 2015-03-13 Jakub Mielczarek , Thomas Cailleteau , Julien Grain , Aurelien Barrau

In arXiv:2603.18175, the authors argue, based on numerical studies of particular cases, that the quantum damping of cosmological shear in a modified loop quantum cosmological model (mLQC-I) that was recently found in arXiv:2510.14021 is not…

General Relativity and Quantum Cosmology · Physics 2026-04-13 Wen-Cong Gan , Leila L. Graef , Rudnei O. Ramos , Gustavo S. Vicente , Anzhong Wang

Loop quantum cosmology is a tentative approach to model the universe down to the Planck era where quantum gravity settings are needed. The quantization of the universe as a dynamical space-time is inspired by Loop Quantum Gravity ideas. In…

General Relativity and Quantum Cosmology · Physics 2016-08-03 J. Grain

We review inflationary cosmology in modified gravity such as $R^2$ gravity with its extensions in order to generalize the Starobinsky inflation model. In particular, we explore inflation realized by three kinds of effects: modification of…

High Energy Physics - Theory · Physics 2015-03-11 Kazuharu Bamba , Sergei D. Odintsov

The fundamental theory and the semiclassical description of loop quantum cosmology (LQC) have been studied in the Friedmann-Robertson-Walker and Bianchi I models. As an extension to include both anisotropy and intrinsic curvature, this…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Dah-Wei Chiou

We perform a LQC-quantization of the FRW cosmological model with nonminimally coupled scalar field. Making use of a canonical transformation, we recast the theory in the minimally coupled form (Einstein frame), for which standard LQC…

General Relativity and Quantum Cosmology · Physics 2013-05-21 Michal Artymowski , Andrea Dapor , Tomasz Pawlowski

This review article aims at presenting the theory of inflation. We first describe the background spacetime behavior during the slow-roll phase and analyze how inflation ends and the Universe reheats. Then, we present the theory of…

High Energy Physics - Theory · Physics 2009-11-10 Jerome Martin

We construct and study Loop Quantum Cosmology (LQC) when the Barbero-Immirzi parameter takes the complex value $\gamma=\pm i$. We refer to this new quantum cosmology as complex Loop Quantum Cosmology. We proceed in making an analytic…

General Relativity and Quantum Cosmology · Physics 2015-06-22 Jibril Ben Achour , Julien Grain , Karim Noui

While the standard, six-parameter, spatially flat $\Lambda$CDM model has been highly successful, certain anomalies in the cosmic microwave background bring out a tension between this model and observations. The statistical significance of…

General Relativity and Quantum Cosmology · Physics 2021-09-21 Abhay Ashtekar , Brajesh Gupt , V. Sreenath

Cosmological models where the standard big bang is replaced by a bounce have been studied for decades. The situation has, however, dramatically changed in the past years for two reasons: first, because new ways to probe the early Universe…

Cosmology and Nongalactic Astrophysics · Physics 2011-01-17 J. Grain , A. Barrau , T. Cailleteau , J. Mielczarek

Phenomenological effect of the super-inflation in loop quantum cosmology (LQC) is discussed. We investigate the case that the Universe is filled with the interacting field between massive scalar field and radiation. Considering the damping…

General Relativity and Quantum Cosmology · Physics 2013-11-28 Kui Xiao , Xiao-Kai He , Jian-Yang Zhu

We develop a consistent analytic approach to determine the conditions under which slow roll inflation can arise when the inflaton is the same scalar field that is responsible for the bounce in Loop Quantum Cosmology (LQC). We find that the…

General Relativity and Quantum Cosmology · Physics 2019-11-04 Anshuman Bhardwaj , Edmund J. Copeland , Jorma Louko

Bouncing cosmologies are obtained by adding to the Einstein-Hilbert action a term of the form $\sqrt{-g}f(\chi)$, with $\chi$ a scalar depending on the Hubble parameter only, not on its derivatives, and which is here shown to arise from the…

General Relativity and Quantum Cosmology · Physics 2018-11-02 Jaume de Haro , Llibert Aresté Saló , Emili Elizalde

An improved Hamiltonian constraint operator is introduced in loop quantum cosmology. Quantum dynamics of the spatially flat, isotropic model with a massless scalar field is then studied in detail using analytical and numerical methods. The…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Abhay Ashtekar , Tomasz Pawlowski , Parampreet Singh

This chapter provides a review of the frameworks developed for cosmological perturbation theory in loop quantum cosmology, and applications to various models of the early universe including inflation, ekpyrosis and the matter bounce, with…

General Relativity and Quantum Cosmology · Physics 2024-03-08 Ivan Agullo , Anzhong Wang , Edward Wilson-Ewing

With a well-motivated extension of higher order holonomy corrections, the quantum theory of loop quantum cosmology (LQC) for the $k=0$ Friedmann-Robertson-Walker model (with a free massless scalar) is rigorously formulated. The analytical…

General Relativity and Quantum Cosmology · Physics 2009-08-18 Dah-Wei Chiou , Li-Fang Li

We discuss the way non-perturbative quantization of cosmological spacetimes in loop quantum cosmology provides insights on the physics of Planck scale and the resolution of big bang singularity. In recent years, rigorous examination of…

General Relativity and Quantum Cosmology · Physics 2009-03-27 Parampreet Singh

In the standard inflationary paradigm the inhomogeneities observed in the CMB arise from quantum fluctuations of an initially homogeneous and isotropic vacuum state. This picture suffers from two well-known weaknesses. First, it assumes…

General Relativity and Quantum Cosmology · Physics 2026-01-21 Gabriel R. Bengochea , Gabriel Leon , Alejandro Perez

The existence of a quantum bounce in isotropic spacetimes is a key result in loop quantum cosmology (LQC), which has been demonstrated to arise in all the models studied so far. In most of the models, the bounce has been studied using…

General Relativity and Quantum Cosmology · Physics 2017-06-20 Peter Diener , Brajesh Gupt , Parampreet Singh

Loop quantum cosmology tries to capture the main ideas of loop quantum gravity and to apply them to the Universe as a whole. Two main approaches within this framework have been considered to date for the study of cosmological perturbations:…

General Relativity and Quantum Cosmology · Physics 2015-10-08 B. Bolliet , J. Grain , C. Stahl , L. Linsefors , A. Barrau