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A Darboux theorem for Hamiltonian operators in the formal calculus of variations

Ezra Getzler
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Abstract

We prove a Darboux theorem for formal deformations of Hamiltonian operators of hydrodynamic type (Dubrovin-Novikov). Not all deformations are equivalent to the original operator: there is a moduli 2-stack of normal forms. The paper utilizes three main concepts: 1) dg Lie algebras concentrated in degrees [-1,\infty) such as the Schouten algebra - these give a convenient language for describing deformation problems; 2) the Deligne 2-groupoid associated to such a dg Lie algebra, which represents the moduli of formal deformations; 3) a refined version of the Schouten bracket in the formal calculus of variations, due to V. O. Soloviev (hep-th/9305133).

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Ezra Getzler. 2000-08-10. A Darboux theorem for Hamiltonian operators in the formal calculus of variations. https://arxiv.org/abs/math/0002164

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