Results 51 to 60 of about 47,027 (304)

An Overview of the Effectiveness of Bicycle Helmet Designs in Impact Testing

Frontiers in Bioengineering and Biotechnology, 2021
Cycling accidents are the leading cause of sports-related head injuries in the US. Conventional bicycle helmets typically consist of polycarbonate shell over Expanded Polystyrene (EPS) foam and are tested with drop tests to evaluate a helmet’s ability to
Javid Abderezaei, Fargol Rezayaraghi, Brigit Kain, Andrea Menichetti, Mehmet Kurt, Mehmet Kurt   +5 more
doaj   +1 more source

Spin Foam Vertex Amplitudes on Quantum Computer—Preliminary Results

Universe, 2019
Vertex amplitudes are elementary contributions to the transition amplitudes in the spin foam models of quantum gravity. The purpose of this article is to make the first step towards computing vertex amplitudes with the use of quantum algorithms.
Jakub Mielczarek
doaj   +1 more source

Loop quantization from a lattice gauge theory perspective [PDF]

, 2004
We present an interpretation of loop quantization in the framework of lattice gauge theory. Within this context the lack of appropriate notions of effective theories and renormalization group flow exhibit loop quantization as an incomplete framework ...
Zapata, José A.
core   +1 more source

Lorentzian Quantum Cosmology from Effective Spin Foams

Universe
Effective spin foams provide the most computationally efficient spin foam models yet and are therefore ideally suited for applications, e.g., to quantum cosmology.
Bianca Dittrich, José Padua-Argüelles
doaj   +1 more source

Asymptotics of 4d spin foam models [PDF]

General Relativity and Gravitation, 2010
10 pages, Proceedings for the 2nd Corfu summer school and workshop on quantum gravity and quantum geometry, talk given by Winston J ...
Frank Hellmann, John W. Barrett, Richard J. Dowdall, Henrique Gomes, Roberto Pereira, Winston J. Fairbairn, Winston J. Fairbairn   +6 more
openaire   +5 more sources

The Feynman propagator for quantum gravity: spin foams, proper time, orientation, causality and timeless-ordering

, 2004
We discuss the notion of causality in Quantum Gravity in the context of sum-over-histories approaches, in the absence therefore of any background time parameter.
Oriti, Daniele
core   +4 more sources

On knottings in the physical Hilbert space of LQG as given by the EPRL model [PDF]

, 2010
We consider the EPRL spin foam amplitude for arbitrary embedded two-complexes. Choosing a definition of the face- and edge amplitudes which lead to spin foam amplitudes invariant under trivial subdivisions, we investigate invariance properties of the ...
Barrett J, Barrett J, Benjamin Bahr, Bianchi E Regoli D Rovelli C, Bojowald M Perez A, Edmonds A R, Freidel L, Freidel L Livine E, Freidel L Speziale S, Kaminski W, Kaminski W, Livine E, Noui K, Perez A, Rovelli C, Rovelli C, Rovelli C, Sahlmann H   +17 more
core   +1 more source

A New Spin Foam Model for 4d Gravity

, 2008
Starting from Plebanski formulation of gravity as a constrained BF theory we propose a new spin foam model for 4d Riemannian quantum gravity that generalises the well-known Barrett-Crane model and resolves the inherent to it ultra-locality problem.
Alexandrov S, Ashtekar A, Baez J C, Baez J C, Baratin A, Barrett J W, Barrett J W, Buffenoir E, Capovilla R, De Pietri R, Engle J Livine E Pereira R Rovelli C, Engle J Pereira R Rovelli C, Freidel L, Freidel L, Freidel L, Gelfand I M, Kirill Krasnov, Laurent Freidel, Livine E R Speziale S, Perelomov A, Ponzano G, Reisenberger M P, Reisenberger M P   +22 more
core   +1 more source

Spin Foams, Refinement Limit, and Renormalization

, 2023
This preprint is to appear as a chapter in "Handbook of Quantum Gravity" (Editors: C. Bambi, L. Modesto and I.L. Shapiro), Springer.
Asante, Seth K., Dittrich, Bianca, Steinhaus, Sebastian   +2 more
openaire   +2 more sources

Altered Dynamic Functional Network Connectivity in Post‐Stroke Aphasia

Annals of Clinical and Translational Neurology, EarlyView.
ABSTRACT Objective Previous studies examining post‐stroke aphasia (PSA) patients via resting‐state functional magnetic resonance imaging (rs‐fMRI) have predominantly focused on static functional connectivity. In contrast, the current investigation aims to elucidate the alterations in dynamic functional network connectivity (dFNC) among PSA patients ...
Guihua Xu, Yongsheng Wu, Junyu Qu, Rui Zhu, Wenwen Xu, Jiaxiang Xin, Dawei Wang   +6 more
wiley   +1 more source