Demontis, Francesco, Ortenzi, Giovanni and Sommacal, Matteo (2018) Heisenberg ferromagnetism as an evolution of a spherical indicatrix: localized solutions and elliptic dispersionless reduction. Electronic Journal of Differential Equations, 2018 (106). pp. 134. ISSN 10726691

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Abstract
A geometrical formulation of Heisenberg ferromagnetism as an evolution of a curve on the unit sphere in terms of intrinsic variables is provided and investigated. Given a vortex filament moving in an incompressible Euler fluid with constant density (under the local induction approximation hypotheses), the solutions of the classical Heisenberg ferromagnet equation are represented by the corresponding spherical (or tangent) indicatrix. The equations for the time evolution of the indicatrix on the unit sphere are given explicitly in terms of two intrinsic variables, the geodesic curvature and the arclength of the curve. Notably, by considering the evolution with respect to slow variables and neglecting the dispersive terms, a novel elliptic dispersionless reduction of the Heisenberg ferromagnet model is obtained. The length of the spherical indicatrix is proved not to be conserved. Finally, a totally explicit algorithm is provided, allowing to construct a solution of the Heisenberg ferromagnet equation from a solution of Nonlinear Schrodinger equation, and, remarkably, viceversa, allowing to construct a solution of Nonlinear Schrodinger equation from a solution of the Heisenberg ferromagnet equation. As expected from the ZakharovTakhtajan gauge equivalence, in the reflectionless case such a twoway map between solutions is shown to preserve the Inverse Scattering Transform spectra, and thus the localization.
Item Type:  Article 

Subjects:  G100 Mathematics 
Department:  Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering 
Depositing User:  Becky Skoyles 
Date Deposited:  24 May 2018 10:43 
Last Modified:  12 Oct 2019 11:03 
URI:  http://nrl.northumbria.ac.uk/id/eprint/34357 
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