Magnetohydrodynamics as a field theory: topological and group theoretical aspects
Seminar Room 1, Newton Institute
The combination of electrodynamic fields and flow fields yields the novel field theory of magnetohydrodynamics . This field theory has unique topological and symmetry properties which are absent in each of one of its ingredients. Although the standard equations of magnetohydrodynamics depend on seven quantities: the magnetic vector field B, the velocity vector field V and the density, mathematical analysis  shows that only four scalar functions are needed to describe magnetohydrodynamics. This analysis is based on previous work of Yahalom & Lynden-Bell . The four functions include two surfaces whose intersections consist the magnetic field lines, the part of the velocity field not defined by the co-moving magnetic field and the density. The Lagrangian describing magnetohydrodynamics admits a novel group of diffeomorphism . Moreover, the conservation of the topology of magnetic fields, leads to effects which are classical analogous of the quantum Aharonov-Bohm effect .
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 Asher Yahalom, "A New Diffeomorphism Symmetry Group of
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