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A major unsolved problem in theoretical physics is to reconcile the classical theory of general relativity with quantum mechanics. These lectures will deal with an attempt to describe quantum gravity as a path integral over geometries known…

General Relativity and Quantum Cosmology · Physics 2014-11-20 Jan Ambjorn , Jerzy Jurkiewicz , Renate Loll

Graph structures are ubiquitous throughout the natural sciences. Here we consider graph-structured quantum data and describe how to carry out its quantum machine learning via quantum neural networks. In particular, we consider training data…

Quantum Physics · Physics 2021-03-22 Kerstin Beer , Megha Khosla , Julius Köhler , Tobias J. Osborne

Inspired by the prospect of having discretized spaces emerge from random graphs, we construct a collection of simple and explicit exponential random graph models that enjoy, in an appropriate parameter regime, a roughly constant vertex…

Disordered Systems and Neural Networks · Physics 2021-10-01 Pawat Akara-pipattana , Thiparat Chotibut , Oleg Evnin

In various background independent approaches, quantum gravity is defined in terms of a field propagation kernel: a sum over paths interpreted as a transition amplitude between 3-geometries, expected to project quantum states of the geometry…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Federico Mattei , Carlo Rovelli , Simone Speziale , Massimo Testa

The branching ratio is calculated for three different models of 2d gravity, using dynamical planar phi-cubed graphs. These models are pure gravity, the D=-2 Gaussian model coupled to gravity and the single spin Ising model coupled to…

High Energy Physics - Theory · Physics 2015-06-26 M. G. Harris

Recent advances in emergent geometry and discretized approaches to quantum gravity have relied upon the notion of a discrete measure of graph curvature. We focus on the two main measures that have been studied, the so-called Ollivier-Ricci…

General Relativity and Quantum Cosmology · Physics 2021-06-08 Philip Tee , C. A. Trugenberger

Paths in an appropriate geometry are usually used as trajectories of test particles in geometric theories of gravity. It is shown that non-symmetric geometries possess some interesting quantum features. Without carrying out any quantization…

General Relativity and Quantum Cosmology · Physics 2015-06-25 M. I. Wanas , M. E. Kahil

In contrast to the usual quantum systems which have at most a finite number of open spectral gaps if they are periodic in more than one direction, periodic quantum graphs may have gaps arbitrarily high in the spectrum. This property of…

Quantum Physics · Physics 2020-05-26 Pavel Exner , Ondřej Turek

This is a survey article describing the relationship between quantum curves and topological recursion. A quantum curve is a Schr\"odinger operator-like noncommutative analogue of a plane curve which encodes (quantum) enumerative invariants…

Mathematical Physics · Physics 2015-02-17 Paul Norbury

This paper introduces a novel architecture for Quantum Graph Neural Networks, which is significantly different from previous approaches found in the literature. The proposed approach produces similar outcomes with respect to previous models…

We explain how quantum gravity can be defined by quantizing spacetime itself. A pinpoint is that the gravitational constant G = L_P^2 whose physical dimension is of (length)^2 in natural unit introduces a symplectic structure of spacetime…

High Energy Physics - Theory · Physics 2014-11-21 Hyun Seok Yang

An analysis is made of a moving disturbance using a directed cyclic graph. A statistical approach is used to calculate the alternative positions in space and state of the disturbance with a defined observed time. The probability for a…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Daniel Brown

Black Holes have always played a central role in investigations of quantum gravity. This includes both conceptual issues such as the role of classical singularities and information loss, and technical ones to probe the consistency of…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Martin Bojowald

The physics of quantum gravity is discussed within the framework of topological quantum field theory. Some of the principles are illustrated with examples taken from theories in which space-time is three dimensional.

General Relativity and Quantum Cosmology · Physics 2009-10-28 John W. Barrett

The quantum mechanics is proved to admit no hidden-variable in 1960s, which means the quantum systems are contextual. Revealing the mathematical structure of quantum mechanics is a significant task. We develop the approach of partial…

Quantum Physics · Physics 2024-12-03 Songyi Liu , Yongjun Wang , Baoshan Wang , Jian Yan , Heng Zhou

We propose a theory of quantum gravity which formulates the quantum theory as a nonperturbative path integral, where each spacetime history appears with a weight given by the exponentiated Einstein-Hilbert action of the corresponding causal…

General Relativity and Quantum Cosmology · Physics 2010-05-12 J. Ambjorn , J. Jurkiewicz , R. Loll

A phenomenology for the deep spatial geometry of loop quantum gravity is introduced. In the context of a simple model, an atom of space, it is shown how purely combinatorial structures can affect observations. The angle operator is used to…

General Relativity and Quantum Cosmology · Physics 2014-11-21 Seth A. Major

In a recent paper (arXiv:1412.6000) a general mechanism for emergence of cosmological space-time geometry from a quantum gravity setting was devised and departure from standard dispersion relations for elementary particle were predicted. We…

General Relativity and Quantum Cosmology · Physics 2015-12-16 Ricardo Gallego Torromé , Marco Letizia , Stefano Liberati

General relativity describes the gravitational field geometrically and in a self-interacting way because it couples to all forms of energy, including its own. Both features make finding a quantum theory difficult, yet it is important in the…

General Relativity and Quantum Cosmology · Physics 2011-09-02 Martin Bojowald

We show how quantum many-body systems on hyperbolic lattices with nearest-neighbor hopping and local interactions can be mapped onto quantum field theories in continuous negatively curved space. The underlying lattices have recently been…