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Applications of Nijenhuis geometry II: maximal pencils of multihamiltonian structures of hydrodynamic type

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posted on 02.10.2020, 09:30 by Alexey BolsinovAlexey Bolsinov, Andrey Yu Konyaev, Vladimir S Matveev
We connect two a priori unrelated topics, theory of geodesically equivalent metrics in differential geometry, and theory of compatible infinite dimensional Poisson brackets of hydrodynamic type in mathematical physics. Namely, we prove that a pair of geodesically equivalent metrics such that one is flat produces a pair of such brackets. We construct Casimirs for these brackets and the corresponding commuting flows. There are two ways to produce a large family of compatible Poisson structures from a pair of geodesically equivalent metrics one of which is flat. One of these families is $(n+1)(n+2)/2$ dimensional; we describe it completely and show that it is maximal. Another has dimension $\le n+2$ and is, in a certain sense, polynomial. We show that a nontrivial polynomial family of compatible Poisson structures of dimension $n+2$ is unique and comes from a pair of geodesically equivalent metrics. In addition, we generalise a result of Sinjukov (1961) from constant curvature metrics to arbitrary Einstein metrics.

History

School

  • Science

Department

  • Mathematical Sciences

Published in

arXiv

Publisher

arXiv

Version

SMUR (Submitted Manuscript Under Review)

Rights holder

© The Authors

Publication date

2020-09-16

Notes

comments are welcome

Other identifier

arXiv:2009.07802

Language

en

Depositor

Dr Alexey Bolsinov. Deposit date: 30 September 2020