Zobrazeno 1 - 10
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pro vyhledávání: '"D P Lonie"'
Autor:
Graham Hall, D. P. Lonie
Publikováno v:
Journal of Geometry and Physics. 61:381-399
This paper studies the situation when two four-dimensional Lorentz manifolds (that is, space–times) admit the same (unparametrised) geodesics, that is, when they are projectively related. A review of some known results is given and then the problem
Autor:
D. P. Lonie, G. S. Hall
Publikováno v:
Journal of Physics A: Mathematical and General. 39:2995-3010
This paper considers 4-dimensional manifolds upon which there is a Lorentz metric, h, and a symmetric connection and which are originally assumed unrelated. It then derives sufficient conditions on the metric and connection (expressed through the cur
Publikováno v:
GECCO
Problem structure, or linkage, refers to the interaction between variables in a black-box fitness function. Discovering structure is a feature of a range of algorithms, including estimation of distribution algorithms (EDAs) and perturbation methods (
Publikováno v:
Physics of Plasmas. 6:1374-1377
A region with chaotic magnetic field lines where the magnetic field (B) and plasma velocity (v) are continuous and differentiable and satisfy the dissipative incompressible magnetohydrodynamic equations with magnetic diffusivity η and kinematic visc
Publikováno v:
UKCI
Estimation of distribution algorithms (EDAs) use structure learning to build a statistical model of good solutions discovered so far, in an effort to discover better solutions. The non-zero coefficients of the Walsh transform produce a hypergraph rep
Publikováno v:
Journal of Plasma Physics. 56:507-530
Linear null points of a magnetic field may come together and coalesce at a secondorder null, or vice versa a second-order null may form and split, giving birth to a pair of linear nulls. Such local bifurcations lead to global changes of magnetic topo
Publikováno v:
Journal of Geophysical Research: Space Physics. 101:7631-7646
Magnetic reconnection has traditionally been associated exclusively with the presence of magnetic null points or field lines tangential to a boundary. However, in many cases introducing a three-dimensional perturbation in a two-and-half-dimensional m
Autor:
Graham Hall, D. P. Lonie
Publikováno v:
Classical and Quantum Gravity. 12:1007-1020
Projective collineations in spacetimes, i.e. vector fields generating local groups of geodesic-preserving diffeomorphisms, are studied. The situation for Einstein spaces is resolved completely and some general results are established regarding arbitr
Autor:
D. P. Lonie, Graham Hall
Publikováno v:
Symmetry, Integrability and Geometry: Methods and Applications, Vol 5, p 066 (2009)
A study is made of 4-dimensional Lorentz manifolds which are projectively related, that is, whose Levi-Civita connections give rise to the same (unparameterised) geodesics. A brief review of some relevant recent work is provided and a list of new res
Autor:
D. P. Lonie, Graham Hall
A study is made of the possible holonomy group types of a space-time for which the energy-momentum tensor corresponds to a null or non-null electromagnetic field, a perfect fluid or a massive scalar field. The case of an Einstein space is also includ
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::2e738feb625688e5afdef5a549eb02c2
http://arxiv.org/abs/gr-qc/0310076
http://arxiv.org/abs/gr-qc/0310076