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We study the anisotropic Bianchi type-I cosmological model at late times, taking into account quantum gravitational corrections in the formalism of the exact renormalization group flow of the effective average action for gravity. The…

General Relativity and Quantum Cosmology · Physics 2020-02-24 Rituparna Mandal , Sunandan Gangopadhyay , Amitabha Lahiri

A new routine is proposed to relate Loop Quant Cosmology (LQC) to Loop Quantum Gravity (LQG) from the perspective of effective dynamics. We derive the big-bang singularity resolution and big bounce from the first principle of full canonical…

General Relativity and Quantum Cosmology · Physics 2020-02-12 Muxin Han , Hongguang Liu

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

Motivated by the increasing evidence for the need of a geometry that resembles Bianchi morphology to explain the observed anisotropy in the WMAP data, we have discussed some features of the Bianchi type-$VI_{0}$ universes in the presence of…

General Physics · Physics 2015-06-11 Anirudh Pradhan

In this article, we study the equations driving the dynamics of a Bianchi-I universe described by holonomy corrected effective loop quantum cosmology. We derive the LQC-modified generalized Friedmann equation, which is used as a guide to…

General Relativity and Quantum Cosmology · Physics 2014-07-28 Linda Linsefors , Aurelien Barrau

We investigate classically non-singular bounces caused by dark energy. In the presence of positive spatial curvature, vacuum energy, either in the form of a cosmological constant or a scalar field potential, allows for an open set of…

High Energy Physics - Theory · Physics 2019-06-26 Sebastian F. Bramberger , Jean-Luc Lehners

Some new exact solutions of Einstein's field equations have come forth within the scope of a spatially homogeneous and anisotropic Bianchi type-III space-time filled with barotropic fluid and dark energy by considering a variable…

Cosmology and Nongalactic Astrophysics · Physics 2014-03-20 Hassan Amirhashchi , Anirudh Pradhan , Rekha Jaiswal

Effective equations often provide powerful tools to develop a systematic understanding of detailed properties of a quantum system. This is especially helpful in quantum cosmology where several conceptual and technical difficulties…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Martin Bojowald , Hector Hernandez , Aureliano Skirzewski

We study the effects of a spatially homogenous magnetic field in Bianchi-I cosmological models. The cases of a pure magnetic field and two models with additional dust and a massless scalar field (stiff matter) are also considered. At the…

General Relativity and Quantum Cosmology · Physics 2023-10-31 Roberto Casadio , Alexander Kamenshchik , Panagiotis Mavrogiannis , Polina Petriakova

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

An LRS Bianchi-I space-time model is studied with constant Hubble parameter in $f(R,T)=R+2\lambda T$ gravity. Although a single (primary) matter source is considered, an additional matter appears due to the coupling between matter and…

General Relativity and Quantum Cosmology · Physics 2021-11-16 Vijay Singh , Aroonkumar Beesham

A companion paper provides a proposal for cosmic singularity resolution based upon general features of a bouncing unitary cosmological model in the mini-superspace approximation. This paper analyses novel phenomenology that can be…

General Relativity and Quantum Cosmology · Physics 2018-12-17 Sean Gryb , Karim P. Y. Thébault

We consider the asymptotic behaviour of spatially homogeneous spacetimes of Bianchi type IX close to the singularity (we also consider some of the other Bianchi types, e. g. Bianchi VIII in the stiff fluid case). The matter content is…

General Relativity and Quantum Cosmology · Physics 2015-06-25 Hans Ringstrom

We study Bianchi cosmologies in the ghost-free bigravity theory assuming both metrics to be homogeneous and anisotropic, of the Bianchi class A, which includes types I,II,VI$_0$,VII$_0$,VIII, and IX. We assume the universe to contain a…

High Energy Physics - Theory · Physics 2013-11-08 Kei-ichi Maeda , Mikhail S. Volkov

It has been known that a non-perfect fluid that accounts for dissipative viscous effects can evade a highly anisotropic chaotic mixmaster approach to a singularity. Viscosity is often simply parameterised in this context, so it remains…

General Relativity and Quantum Cosmology · Physics 2022-02-02 Chandrima Ganguly , Jerome Quintin

The dynamics and evolution of Bianchi type I space-times is considered in the framework of the four-dimensional truncation of a reduced theory obtained from the N=2,D=5 supergravity. The general solution of the gravitational field equations…

High Energy Physics - Theory · Physics 2009-10-31 Chiang-Mei Chen , T. Harko , M. K. Mak

A Bianchi IX Mixmaster spacetime is the most general spatially homogeneous solution of Einstein's equations and it can represent the space-averaged Universe. We introduce two novel mechanisms resulting in a Mixmaster Universe with…

General Relativity and Quantum Cosmology · Physics 2019-11-20 Chandrima Ganguly , Marco Bruni

In this work, we study some physical aspects of unitary evolution of Bianchi-I model. In particular, we study the behavior of the volume and the scale factor as a function of time for the Bianchi-I universe with ultra-relativistic fluid…

General Relativity and Quantum Cosmology · Physics 2016-01-28 Sridip Pal

In this work we construct an effective four-dimensional model by compactifying a ten-dimensional theory of gravity coupled with a real scalar dilaton field on a time-dependent torus. This approach is applied to anisotropic cosmological…

General Relativity and Quantum Cosmology · Physics 2016-05-18 L. Toledo Sesma , J. Socorro , O. Loaiza

We explore the relationship between the effective dynamics in standard loop quantum cosmology (LQC) based on holonomies and triads obtained from gauge-fixing fluxes, and a modification of LQC based on holonomies and gauge-covariant fluxes…

General Relativity and Quantum Cosmology · Physics 2022-08-31 Bao-Fei Li , Parampreet Singh