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The inverse problem in the calculus of variations: new developments

Thoan Do, Geoff Prince (2021)

Communications in Mathematics

We deal with the problem of determining the existence and uniqueness of Lagrangians for systems of n second order ordinary differential equations. A number of recent theorems are presented, using exterior differential systems theory (EDS). In particular, we indicate how to generalise Jesse Douglas’s famous solution for n = 2 . We then examine a new class of solutions in arbitrary dimension n and give some non-trivial examples in dimension 3.

The iterated version of a translative integral formula for sets of positive reach

Rataj, Jan (1997)

Proceedings of the 16th Winter School "Geometry and Physics"

By taking into account the work of J. Rataj and M. Zähle [Geom. Dedicata 57, 259-283 (1995; Zbl 0844.53050)], R. Schneider and W. Weil [Math. Nachr. 129, 67-80 (1986; Zbl 0602.52003)], W. Weil [Math. Z. 205, 531-549 (1990; Zbl 0705.52006)], an integral formula is obtained here by using the technique of rectifiable currents.This is an iterated version of the principal kinematic formula for q sets of positive reach and generalized curvature measures.

The jet prolongations of 2 -fibred manifolds and the flow operator

Włodzimierz M. Mikulski (2008)

Archivum Mathematicum

Let r , s , m , n , q be natural numbers such that s r . We prove that any 2 - 𝕄 m , n , q -natural operator A : T 2-proj T J ( s , r ) transforming 2 -projectable vector fields V on ( m , n , q ) -dimensional 2 -fibred manifolds Y X M into vector fields A ( V ) on the ( s , r ) -jet prolongation bundle J ( s , r ) Y is a constant multiple of the flow operator 𝒥 ( s , r ) .

The Laplace-Beltrami operator in almost-Riemannian Geometry

Ugo Boscain, Camille Laurent (2013)

Annales de l’institut Fourier

We study the Laplace-Beltrami operator of generalized Riemannian structures on orientable surfaces for which a local orthonormal frame is given by a pair of vector fields that can become collinear.Under the assumption that the structure is 2-step Lie bracket generating, we prove that the Laplace-Beltrami operator is essentially self-adjoint and has discrete spectrum. As a consequence, a quantum particle cannot cross the singular set (i.e., the set where the vector fields become collinear) and the...

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