Routhian reduction for quasi-invariant Lagrangians

Abstract

In this paper we describe Routhian reduction as a special case of standard symplectic reduction, also called Marsden-Weinstein reduction. We use this correspondence to present a generalization of Routhian reduction for quasi-invariant Lagrangians, i.e. Lagrangians that are invariant up to a total time derivative. We show how functional Routhian reduction can be seen as a particular instance of reduction of a quasi-invariant Lagrangian, and we exhibit a Routhian reduction procedure for the special case of Lagrangians with quasi-cyclic coordinates. As an application we consider the dynamics of a charged particle in a magnetic field.

24 pages, 3 figures

References in corpus (2)

• Routh's procedure for non-Abelian symmetry groups
• Routhian reduction for quasi-invariant Lagrangians

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