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A fully consistent linear perturbation theory for cosmology is derived in the presence of quantum corrections as they are suggested by properties of inverse volume operators in loop quantum gravity. The underlying constraints present a…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Martin Bojowald , Golam Mortuza Hossain , Mikhail Kagan , S. Shankaranarayanan

Different versions of consistent canonical realizations of hypersurface deformations of spherically symmetric space-times have been derived in models of loop quantum gravity, modifying the classical dynamics and sometimes also the structure…

General Relativity and Quantum Cosmology · Physics 2020-02-13 Martin Bojowald , Suddhasattwa Brahma , Ding Ding , Michele Ronco

We present an elegant and simple dynamical model of symmetric, non-degenerate (n x n) matrices of fixed signature defined on a n-dimensional hyper-cubic lattice with nearest-neighbor interactions. We show how this model is related to…

General Relativity and Quantum Cosmology · Physics 2012-12-27 Kyle Tate , Matt Visser

3D Loop Quantum Gravity with a vanishing cosmological constant can be related to the quantization of the $\textrm{SU}(2)$ BF theory discretized on a lattice. At the classical level, this discrete model characterizes discrete flat geometries…

General Relativity and Quantum Cosmology · Physics 2014-12-03 Valentin Bonzom , Maité Dupuis , Florian Girelli

A novel scheme to simulate the evolution of a restricted set of observables of a quantum system is proposed. The set comprises the spectrum-generating algebra of the Hamiltonian. The idea is to consider a certain open-system evolution,…

Quantum Physics · Physics 2009-11-13 M. Khasin , R. Kosloff

Loop Quantum Gravity faces challenges in constructing a well-defined Hamiltonian constraint and understanding the quantum notion of time. In this paper these issues are studied by quantizing the $U(1)^3$ model, a simplified system…

General Relativity and Quantum Cosmology · Physics 2024-12-02 Sepideh Bakhoda , Yongge Ma

We consider a discrete model of euclidean quantum gravity in four dimensions based on a summation over random simplicial manifolds. The action used is the Einstein-Hilbert action plus an $R^2$-term. The phase diagram as a function of the…

High Energy Physics - Theory · Physics 2009-10-22 J. Ambjorn , J. Jurkiewicz , C. F. Kristjansen

If holography is an equivalence between quantum theories, one might expect it to be described by a map that is a bijective isometry between bulk and boundary Hilbert spaces, preserving the hamiltonian and symmetries. Holography has been…

High Energy Physics - Theory · Physics 2020-12-02 Steven B. Giddings

In this review, the fundamental structure of loop quantum gravity is presented pedagogically. Our main aim is to help non-experts to understand the motivations, basic structures, as well as general results. It may also be beneficial to…

General Relativity and Quantum Cosmology · Physics 2011-05-16 Muxin Han , Weiming Huang , Yongge Ma

The canonical ``loop'' formulation of quantum gravity is a mathematically well defined, background independent, non perturbative standard quantization of Einstein's theory of General Relativity. Some among the most meaningful results of the…

General Relativity and Quantum Cosmology · Physics 2012-06-12 R. De Pietri

We present a systematic approach to the kinematics of quantum-reduced loop gravity, a model originally proposed by Alesci and Cianfrani as an attempt to probe the physical implications of loop quantum gravity. We implement the quantum…

General Relativity and Quantum Cosmology · Physics 2024-12-03 Ilkka Mäkinen

We investigate bouncing scenario in the modified $f(T)$ gravity, $T$ being the torsion scalar. Attention is attached to the reconstruction of $f(T)$ able to describe type IV singular bouncing evolution, where we adopt as assumption that the…

General Relativity and Quantum Cosmology · Physics 2019-09-25 P. H. Logbo , M. J. S. Houndjo

We construct physical semi-classical states annihilated by the Hamiltonian constraint operator in the framework of loop quantum cosmology as a method of systematically determining the regime and validity of the semi-classical limit of the…

General Relativity and Quantum Cosmology · Physics 2009-11-11 Parampreet Singh , Kevin Vandersloot

Since there are quantization ambiguities in constructing the Hamiltonian constraint operator in isotropic loop quantum cosmology, it is crucial to check whether the key features of loop quantum cosmology are robust against the ambiguities.…

General Relativity and Quantum Cosmology · Physics 2010-04-14 Jinsong Yang , You Ding , Yongge Ma

We consider two-dimensional quantum gravity endowed with a positive cosmological constant and coupled to a conformal field theory of large and positive central charge. We study cosmological properties at the classical and quantum level. We…

High Energy Physics - Theory · Physics 2025-03-05 Dionysios Anninos , Chiara Baracco , Beatrix Mühlmann

Loop quantum gravity is believed to eliminate singularities such as the big bang and big crunch singularity. This belief is based on studies of so-called loop quantum cosmology which concerns symmetry-reduced models of quantum gravity. In…

General Relativity and Quantum Cosmology · Physics 2017-09-12 Ward Struyve

Understanding strongly interacting quantum matter and quantum gravity are both important open issues in theoretical physics, and the holographic duality between quantum field theory and gravity theory nicely brings these two topics…

Quantum Gases · Physics 2021-06-30 Tian-Gang Zhou , Lei Pan , Yu Chen , Pengfei Zhang , Hui Zhai

First, we review the $C^\ast$-algebraic foundations of loop quantization, in particular, the construction of quantum configuration spaces and the implementation of symmetries. Then, we apply these results to loop quantum gravity, focusing…

Mathematical Physics · Physics 2015-07-21 Christian Fleischhack

Quantum Reduced Loop Gravity provides a promising framework for a consistent characterization of the early Universe dynamics. Inspired by BKL conjecture, a flat Universe is described as a collection of Bianchi I homogeneous patches. The…

General Relativity and Quantum Cosmology · Physics 2015-06-25 Emanuele Alesci , Francesco Cianfrani

We develop a worldline approach to quantum gravity in D=4. Using the background field method we consider the covariantly gauge fixed Einstein-Hilbert action with cosmological constant, and find a worldline representation of the differential…

High Energy Physics - Theory · Physics 2013-06-25 Fiorenzo Bastianelli , Roberto Bonezzi