Results 51 to 60 of about 45,346 (288)

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

A spin-foam vertex amplitude with the correct semiclassical limit [PDF]

, 2013
Spin-foam models are hoped to provide a dynamics for loop quantum gravity. These start from the Plebanski formulation of gravity, in which gravity is obtained from a topological field theory, BF theory, through constraints, which, however, select more ...
Ashtekar, Ashtekar, Ashtekar, Ashtekar, Barbero G., Barrett, Barrett, Barrett, Barrett, Buffenoir, Christodoulou, Conrady, Dirac, Engle, Engle, Engle, Engle, Engle, Freidel, Gambini, Immirzi, Jonathan Engle, Kaminski, Kamiński, Livine, Mikovic, Ooguri, Oriti, Pereira, Perelomov, Perez, Regge, Reisenberger, Reisenberger, Rovelli, Rovelli, Teitelboim, Thiemann, Urbantke   +38 more
core   +2 more sources

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

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

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

Quantum gravity at the fifth root of unity

Physics Open, 2022
We consider quantum transition amplitudes, partition functions and observables for 3D spin foam models within SU(2)quantum group deformation symmetry, where the deformation parameter is postulated to be a complex fifth root of unity.
Marcelo Amaral, Raymond Aschheim, Klee Irwin   +2 more
doaj  

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

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

Some Considerations on Discrete Quantum Gravity

, 2012
Recent results in Local Regge Calculus are confronted with Spin Foam Formalism. Introducing Barrett-Crane Quantization in Local Regge Calculus makes it possible to associate a unique Spin $j_{h}$ with an hinge $h$, fulfilling one of the requirements of ...
Gionti, Gabriele, J, S.
core   +1 more source