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Results from a number of different approaches to quantum gravity suggest that the effective dimension of spacetime may drop to $d=2$ at small scales. I show that two different dimensional estimators in causal set theory display the same…

General Relativity and Quantum Cosmology · Physics 2015-11-18 S. Carlip

The four dimensional Causal Dynamical Triangulations (CDT) approach to quantum gravity is already more than ten years old theory with numerous unprecedented predictions such as non-trivial phase structure of gravitational field and…

General Relativity and Quantum Cosmology · Physics 2015-12-31 Jakub Mielczarek

We measure the spectral dimension of universes emerging from nonperturbative quantum gravity, defined through state sums of causal triangulated geometries. While four-dimensional on large scales, the quantum universe appears two-dimensional…

High Energy Physics - Theory · Physics 2010-04-06 J. Ambjorn , J. Jurkiewicz , R. Loll

We study a formulation of lattice gravity defined via Euclidean dynamical triangulations (EDT). After fine-tuning a non-trivial local measure term we find evidence that four-dimensional, semi-classical geometries are recovered at long…

High Energy Physics - Theory · Physics 2017-01-25 J. Laiho , S. Bassler , D. Coumbe , D. Du , J. T. Neelakanta

Generalized causal dynamical triangulations (generalized CDT) is a model of two-dimensional quantum gravity in which a limited number of spatial topology changes is allowed to occur. We solve the model at the discretized level using…

High Energy Physics - Theory · Physics 2013-07-22 Jan Ambjorn , Timothy G. Budd

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

We define a new scaling limit of matrix models which can be related to the method of causal dynamical triangulations (CDT) used when investigating two-dimensional quantum gravity. Surprisingly, the new scaling limit of the matrix models is…

High Energy Physics - Theory · Physics 2008-12-18 J. Ambjorn , R. Loll , Y. Watabiki , W. Westra , S. Zohren

We propose a toy model of quantum gravity in two dimensions with Euclidean signature. The model is given by a kind of discretization which is different from the dynamical triangulation. We show that there exists a continuum limit and we can…

High Energy Physics - Theory · Physics 2017-08-28 Marcello Rotondo , Shin'ichi Nojiri

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

We provide detailed evidence for the claim that nonperturbative quantum gravity, defined through state sums of causal triangulated geometries, possesses a large-scale limit in which the dimension of spacetime is four and the dynamics of the…

High Energy Physics - Theory · Physics 2010-04-06 J. Ambjorn , J. Jurkiewicz , R. Loll

This topical review gives a comprehensive overview and assessment of recent results in Causal Dynamical Triangulations (CDT), a modern formulation of lattice gravity, whose aim is to obtain a theory of quantum gravity nonperturbatively from…

High Energy Physics - Theory · Physics 2020-01-08 R. Loll

I propose two scale-dependent measures of the homogeneity of the quantum geometry determined by an ensemble of causal triangulations. The first measure is volumetric, probing the growth of volume with graph geodesic distance. The second…

General Relativity and Quantum Cosmology · Physics 2014-12-24 Joshua H. Cooperman

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

Four-dimensional CDT (causal dynamical triangulations) is a lattice theory of geometries which one might use in an attempt to define quantum gravity non-perturbatively, following the standard procedures of lattice field theory. Being a…

High Energy Physics - Theory · Physics 2020-03-19 J. Ambjorn , D. Coumbe , J. Gizbert-Studnicki , A. Görlich , J. Jurkiewicz

The formalism of causal dynamical triangulations (CDT) provides us with a non-perturbatively defined model of quantum gravity, where the sum over histories includes only causal space-time histories. Path integrals of CDT and their continuum…

General Relativity and Quantum Cosmology · Physics 2008-11-26 J. Ambjorn , R. Loll , W. Westra , S. Zohren

The seemingly universal phenomenon of scale-dependent effective dimensions in non-perturbative theories of quantum gravity has been shown to be a potential source of quantum gravity phenomenology. The scale-dependent effective dimension…

General Relativity and Quantum Cosmology · Physics 2023-05-16 Marcus Reitz , Dániel Németh , Damodar Rajbhandari , Andrzej Görlich , Jakub Gizbert-Studnicki

We show recent results of the application of spectral analysis in the setting of the Monte Carlo approach to Quantum Gravity known as Causal Dynamical Triangulations (CDT), discussing the behavior of the lowest lying eigenvalues of the…

High Energy Physics - Lattice · Physics 2019-12-25 Giuseppe Clemente , Massimo D'Elia , Alessandro Ferraro

Motivated by the search for new observables in nonperturbative quantum gravity, we consider Causal Dynamical Triangulations (CDT) in 2+1 dimensions with the spatial topology of a torus. This system is of particular interest, because one can…

High Energy Physics - Theory · Physics 2013-07-11 T. G. Budd , R. Loll

The Causal Dynamical Triangulation (CDT) approach to quantum gravity is a lattice approximation to the gravitational path integral. Developed by Ambj\o{}rn, Jurkiewicz and Loll, it has yielded some important results, notably the emergence…

General Relativity and Quantum Cosmology · Physics 2015-06-03 Rajesh Kommu

A generic prediction of quantum gravity is the vacuum dispersion of light, and hence that a photon's speed depends on its energy. We present further numerical evidence for a scale dependent speed of light in the causal dynamical…

High Energy Physics - Theory · Physics 2017-05-01 Daniel Coumbe