Morse theory on spaces of braids and Lagrangian dynamics
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.
Cite
@article{arxiv.math/0105082,
title = {Morse theory on spaces of braids and Lagrangian dynamics},
author = {R. W. Ghrist and J. B. Van den Berg and R. C. Vandervorst},
journal= {arXiv preprint arXiv:math/0105082},
year = {2007}
}
Comments
Revised version: numerous changes in exposition. Slight modification of two proofs and one definition; 55 pages, 20 figures