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We attempt to find new symmetries in the space-time structure, leading to a modified gravitation at large length scales, which provides the foundations of a quantum gravity at very low energies. This search begins by considering a unified…

General Relativity and Quantum Cosmology · Physics 2007-09-13 Claudio Nassif

In the approach of Causal Dynamical Triangulations (CDT), quantum gravity is obtained as a scaling limit of a non-perturbative path integral over space-times whose causal structure plays a crucial role in the construction. After some…

General Relativity and Quantum Cosmology · Physics 2018-11-30 L. Glaser , R. Loll

We search for a continuum limit in the causal dynamical triangulation (CDT) approach to quantum gravity by determining the change in lattice spacing using two independent methods. The two methods yield similar results that may indicate how…

High Energy Physics - Theory · Physics 2016-05-25 Jan Ambjorn , Daniel Coumbe , Jakub Gizbert-Studnicki , Jerzy Jurkiewicz

Lorentz invariance violation in quantum gravity (QG) models or a nonzero photon mass, $m_\gamma$, would lead to an energy-dependent propagation speed for photons, such that photons of different energies from a distant source would arrive at…

General Relativity and Quantum Cosmology · Physics 2021-11-19 Deaglan J. Bartlett , Harry Desmond , Pedro G. Ferreira , Jens Jasche

Causal Dynamical Triangulations is a background independent approach to quantum gravity. We show that there exists an effective transfer matrix labeled by the scale factor which properly describes the evolution of the quantum universe. In…

High Energy Physics - Theory · Physics 2013-02-13 Andrzej Görlich

The method of four-dimensional Causal Dynamical Triangulations provides a background-independent definition of the sum over geometries in quantum gravity, in the presence of a positive cosmological constant. We present the evidence…

High Energy Physics - Theory · Physics 2007-05-23 J. Ambjorn , J. Jurkiewicz , R. Loll

Quantum Mechanics of photons leads to a theory of Quantum Gravity that nicely matches the experimental results of varying fine structure constant,obtained from many-multiplet Quaser absorption systems and atomic clocks.The variation of that…

General Physics · Physics 2016-09-08 Pradip Kumar Chatterjee

Lattice formulations of gravity can be used to study non-perturbative aspects of quantum gravity. Causal Dynamical Triangulations (CDT) is a lattice model of gravity that has been used in this way. It has a built-in time foliation but is…

General Relativity and Quantum Cosmology · Physics 2021-03-30 J. Ambjorn , Z. Drogosz , J. Gizbert-Studnicki , A. Görlich , J. Jurkiewicz , D. Nèmeth

Phenomenological approaches to quantum gravity try to infer model-independent laws by analyzing thought experiments and combining both quantum, relativistic, and gravitational ingredients. We first review these ingredients -three basic…

General Relativity and Quantum Cosmology · Physics 2013-08-21 Jean-Philippe Bruneton

We advocate lattice methods as the tool of choice to constructively define a background-independent theory of Lorentzian quantum gravity and explore its physical properties in the Planckian regime. The formulation that arguably has most…

High Energy Physics - Lattice · Physics 2011-05-30 J. Ambjorn , J. Jurkiewicz , R. Loll

Within the asymptotic safety scenario for gravity various conceptual issues related to the scale dependence of the metric are analyzed. The running effective field equations implied by the effective average action of Quantum Einstein…

High Energy Physics - Theory · Physics 2010-10-27 Martin Reuter , Jan-Markus Schwindt

Quantum gravity can determine the dependence of gauge couplings in a scalar field, which is related to possible fifth forces and time varying fundamental "constants". This prediction is based on the scaling solution of functional flow…

High Energy Physics - Theory · Physics 2022-11-30 C. Wetterich

Causal Dynamical Triangulations (CDT) is a methodology to define and compute the gravitational path integral, whose aim is a fully fledged nonperturbative quantum field theory of gravity and spacetime. Analogous to lattice formulations of…

High Energy Physics - Theory · Physics 2026-04-08 J. Ambjørn , R. Loll

In these lectures we describe how a theory of quantum gravity may be constructed in terms of a lattice formulation based on so-called causal dynamical triangulations (CDT). We discuss how the continuum limit can be obtained and how to…

High Energy Physics - Theory · Physics 2010-07-16 J. Ambjorn , A. Goerlich , J. Jurkiewicz , R. Loll

We study the spatial dependence of the quantum friction effect for an atom moving at a constant velocity, in a parallel direction to a material plane. In particular, we determine the probability per unit time and unit area, for exciting…

Quantum Physics · Physics 2022-09-29 Aitor Fernández , César D. Fosco

Any canonical quantum theory can be understood to arise from the compatibility of the statistical geometry of distinguishable observations with the canonical Poisson structure of Hamiltonian dynamics. This geometric perspective offers a…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Vishnu Jejjala , Djordje Minic , Chia-Hsiung Tze

The scale dependent effective average action for quantum gravity complies with the fundamental principle of Background Independence. Ultimately the background metric it formally depends on is selected self-consistently by means of a…

General Relativity and Quantum Cosmology · Physics 2020-01-08 Carlo Pagani , Martin Reuter

"Causal Dynamical Triangulations" (CDT) represent a lattice regularization of the sum over spacetime histories, providing us with a non-perturbative formulation of quantum gravity. The ultraviolet fixed points of the lattice theory can be…

High Energy Physics - Theory · Physics 2015-06-15 J. Ambjorn , A. Goerlich , J. Jurkiewicz , R. Loll

Quantum gravity is studied in a semiclassical approximation and it is found that to first order in the Planck length the effect of quantum gravity is to make the low energy effective spacetime metric energy dependent. The diffeomorphism…

High Energy Physics - Theory · Physics 2009-11-11 Lee Smolin

Quantum gravity phenomenology has been historically regarded as a difficult endeavour, due to the apparent scarcity of phenomena involving the required scales of length (Planck length $l_P$) and energy (Planck energy $E_P$). It was…

High Energy Physics - Phenomenology · Physics 2023-10-10 Andrea Bevilacqua , Jerzy Kowalski-Glikman , Wojciech Wislicki