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It is known that in loop quantum cosmology (LQC) the universe avoids the singularity by a bounce when the matter density approaches the critical density $\rho_c$ (the order of Planck density). After incorporating the inverse volume…

General Relativity and Quantum Cosmology · Physics 2011-03-14 Hua-Hui Xiong , Jian-Yang Zhu

The "improved dynamics" of loop quantum cosmology is extended to include anisotropies of the Bianchi I model. As in the isotropic case, a massless scalar field serves as a relational time parameter. However, the extension is non-trivial…

General Relativity and Quantum Cosmology · Physics 2010-04-14 Abhay Ashtekar , Edward Wilson-Ewing

In bouncing cosmological models, either classical or quantum, the big bang singularity is replaced by a regular bounce. A challenging question in such models is how to keep the shear under control in the contracting phase, as it is…

General Relativity and Quantum Cosmology · Physics 2026-05-28 Christian Brown , Jared Fier , Brian Phillips , Gerald Cleaver , Anzhong Wang

Four-dimensional gravitational theories derived from an infinite sum of Lovelock curvature invariants, combined with a conformal rescaling of the metric, are equivalent to a subclass of shift-symmetric Horndeski theories that possess a…

General Relativity and Quantum Cosmology · Physics 2025-07-30 Shinji Tsujikawa

We quantize to completion an inflationary universe with small inhomogeneities in the framework of loop quantum cosmology. The homogeneous setting consists of a massive scalar field propagating in a closed, homogeneous scenario. We provide a…

General Relativity and Quantum Cosmology · Physics 2012-07-20 Mikel Fernández-Méndez , Guillermo A. Mena Marugán , Javier Olmedo

In this Letter, we study analytically the evolutions of the flat Friedmann-Lemaitre-Robertson-Walker (FLRW) universe and its linear perturbations in the framework of {\em the dressed metric approach} in loop quantum cosmology (LQC).…

General Relativity and Quantum Cosmology · Physics 2017-09-21 Tao Zhu , Anzhong Wang , Klaus Kirsten , Gerald Cleaver , Qin Sheng

Horava-Lifshitz gravity, a recent proposal for a UV-complete renormalizable gravity theory, may lead to a bouncing cosmology. In this note we argue that Horava-Lifshitz cosmology may yield a concrete realization of the matter bounce…

High Energy Physics - Theory · Physics 2013-05-29 Robert Brandenberger

Quantum gravity has matured over the last decade to a theory which can tell in a precise and explicit way how cosmological singularities of general relativity are removed. A branch of the universe "before" the classical big bang is obtained…

Astrophysics · Physics 2007-05-23 Martin Bojowald

This paper discusses the problem of inflation in the context of Friedmann-Robertson-Walker Cosmology. We show how, after a simple change of variables, one can quantize the problem in a way which parallels the classical discussion. The…

High Energy Physics - Theory · Physics 2007-05-23 Marvin Weinstein , Ratin Akhoury

In this Essay we investigate the observational signatures of Loop Quantum Cosmology (LQC) in the CMB data. First, we concentrate on the dynamics of LQC and we provide the basic cosmological functions. We then obtain the power spectrum of…

General Relativity and Quantum Cosmology · Physics 2017-11-22 Spyros Basilakos , Vahid Kamali , Ahmad Mehrabi

Unifying the early-universe inflationary paradigm with late-time cosmic acceleration, while resolving the initial Big Bang singularity, remains one of the most profound challenges in modern cosmology. In this paper, we propose a…

General Relativity and Quantum Cosmology · Physics 2026-05-20 Zhiming Shuai , Xiangdong Zhang

We present a gauge-invariant treatment of singularity resolution using loop quantum gravity techniques with respect to local SU(2) transformations. Our analysis reveals many novel features of quantum geometry which were till now hidden in…

General Relativity and Quantum Cosmology · Physics 2020-03-31 Klaus Liegener , Parampreet Singh

We introduce a new regularization scheme for Quantum Cosmology in Loop Quantum Gravity (LQG) using the tools of Quantum Reduced Loop Gravity (QRLG). It is obtained considering density matrices for superposition of graphs based on…

General Relativity and Quantum Cosmology · Physics 2019-01-23 Emanuele Alesci , Gioele Botta , Gabriele V. Stagno

We analyze the big bounce transition of the quantum FRW model in the setting of the nonstandard loop quantum cosmology (LQC). Elementary observables are used to quantize compound observables. The spectrum of the energy density operator is…

General Relativity and Quantum Cosmology · Physics 2015-05-20 Wlodzimierz Piechocki

Loop quantum cosmology (LQC) is used to provide concrete evidence in support of the general paradigm underlying spin foam models (SFMs). Specifically, it is shown that: i) the physical inner product in the timeless framework equals the…

General Relativity and Quantum Cosmology · Physics 2009-12-10 Abhay Ashtekar , Miguel Campiglia , Adam Henderson

As is known, in modified cosmological theories of gravity many of the cosmologies which could not be generated by standard Einstein gravity, can be consistently described by $F(R)$ theories. Using known reconstruction techniques, we…

General Relativity and Quantum Cosmology · Physics 2015-09-16 V. K. Oikonomou

This work studies the quantum cosmology of a closed, spatially homogeneous, and isotropic FLRW minisuperspace model with electromagnetic radiation as a matter content. We solve the associated Wheeler-DeWitt (WDW) equation using the…

General Relativity and Quantum Cosmology · Physics 2023-04-20 S. Jalalzadeh , A. Mohammadi , D. Demir

We present results concerning the nature of the cosmological big bounce(BB) transition within the loop geometry underlying loop quantum cosmology (LQC). Our canonical quantization method is an alternative to the standard LQC. An evolution…

General Relativity and Quantum Cosmology · Physics 2014-11-20 Wlodzimierz Piechocki

In this paper we take matter source with non-linear Equation of state (EoS) that has produced non-singular Emergent cosmology for spatially flat universe in General Relativity and minimally coupled scalar field with two different potentials…

General Relativity and Quantum Cosmology · Physics 2023-10-23 Rikpratik Sengupta , B. C. Paul , M. Kalam , P. Paul , A. Aich

We prove that in the Hartle-Hawking approach to quantum cosmology the existence of an inflationary phase is a general property of minisuperspace models given by a closed Friedmann-Robertson-Walker universe containing a massless scalar field…

General Relativity and Quantum Cosmology · Physics 2010-04-06 Giampiero Esposito , Giovanni Platania