Results 81 to 90 of about 1,243 (181)

Relational Observables in Gravity: a Review

Symmetry, Integrability and Geometry: Methods and Applications, 2012
We present an overview on relational observables in gravity mainly from a loop quantum gravity perspective. The gauge group of general relativity is the diffeomorphism group of the underlying manifold.
Johannes Tambornino
doaj   +1 more source

The Holst spin foam model via cubulations

New Journal of Physics, 2012
Spin foam models are an attempt at a covariant or path integral formulation of canonical loop quantum gravity. The construction of such models usually relies on the Plebanski formulation of general relativity as a constrained BF theory and is based on ...
Aristide Baratin, Cecilia Flori, Thomas Thiemann   +2 more
doaj   +1 more source

Symmetric configurations highlighted by collective quantum coherence

European Physical Journal C: Particles and Fields, 2017
Recent developments in quantum gravity have shown the Lorentzian treatment to be a fruitful approach towards the emergence of macroscopic space-times. In this paper, we discuss another related aspect of the Lorentzian treatment: we argue that collective ...
Dennis Obster, Naoki Sasakura
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Canonical “Loop” Quantum Gravity and Spin Foam Models [PDF]

, 2000
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 theory are: 1) the complete calculation of the spectrum of geometric quantities like the area and the volume and ...
openaire   +3 more sources

Relational Lorentzian Asymptotically Safe Quantum Gravity: Showcase Model

Universe
In a recent contribution, we identified possible points of contact between the asymptotically safe and canonical approaches to quantum gravity. The idea is to start from the reduced phase space (often called relational) formulation of canonical quantum ...
Renata Ferrero, Thomas Thiemann
doaj   +1 more source

Symplectic Structure of Intrinsic Time Gravity

Universe, 2016
The Poisson structure of intrinsic time gravity is analysed. With the starting point comprising a unimodular three-metric with traceless momentum, a trace-induced anomaly results upon quantization.
Eyo Eyo Ita, Amos S. Kubeka
doaj   +1 more source

Tunnelling to holographic traversable wormholes

SciPost Physics
We study nonperturbative effects of quantum gravity in a system consisting of a coupled pair of holographic CFTs. The AdS$_4$/CFT$_3$ system has three possible ground states: two copies of empty AdS, a pair of extremal AdS black holes, and an eternal AdS
Suzanne Bintanja, Ben Freivogel, Andrew Rolph
doaj   +1 more source

From Timeless Physical Theories to Timelessness

Humana.Mente: Journal of Philosophical Studies, 2018
This paper addresses the extent to which both Julian Barbour‘s Machian formulation of general relativity and his interpretation of canonical quantum gravity can be called timeless. We differentiate two types of timelessness in Barbour‘s (1994a, 1994b and
Samuel Baron, Peter Evans, Kristie Miller   +2 more
doaj  

Emergent Time and Time Travel in Quantum Physics

Universe
Entertaining the possibility of time travel will invariably challenge dearly-held concepts in fundamental physics. It becomes relatively easy to construct multiple logical contradictions using differing starting points from various well-established ...
Ana Alonso-Serrano, Sebastian Schuster, Matt Visser   +2 more
doaj   +1 more source

A quantum theory of gravity

European Physical Journal C: Particles and Fields
We develop a covariant Hamiltonian formalism in which evolution is measured along the proper-time flow of an observer congruence, replacing the external coordinate-time derivative with the Lie derivative. Our formalism keeps the Hamiltonian split between
Antonio Peña Peña
doaj   +1 more source