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Morse theory on spaces of braids and Lagrangian dynamics

R. W. Ghrist·J. B. Van den Berg·R. C. Vandervorst
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Abstract

In the first half of the paper we construct a Morse-type theory on certain spaces of braid diagrams. We define a topological invariant of closed positive braids which is correlated with the existence of invariant sets of parabolic flows defined on discretized braid spaces. Parabolic flows, a type of one-dimensional lattice dynamics, evolve singular braid diagrams in such a way as to decrease their topological complexity; algebraic lengths decrease monotonically. This topological invariant is derived from a Morse-Conley homotopy index and provides a gloablization of `lap number' techniques used in scalar parabolic PDEs. In the second half of the paper we apply this technology to second order Lagrangians via a discrete formulation of the variational problem. This culminates in a very general forcing theorem for the existence of infinitely many braid classes of closed orbits.

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BibTeXRIS

R. W. Ghrist, J. B. Van den Berg, R. C. Vandervorst. 2002-10-03. Morse theory on spaces of braids and Lagrangian dynamics. https://arxiv.org/abs/math/0105082

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