Morse theory and moduli spaces of self-avoiding polygonal linkages

We show that a smooth $d$-manifold $M$ is diffeomorphic to ${\mathbb{R}}^d$ if it admits a Lyapunov-Reeb function, i.e., a smooth map $f:M\to \mathbb{R}$ that is proper, lower-bounded, and has a unique critical point. By constructing such functions, we prove that the moduli spaces of self-avoiding polygonal linkages and configurations are diffeomorphic to Euclidean spaces. This resolves the Refined Carpenter’s Rule Problem and confirms a conjecture proposed by González and Sedano-Mendoza. Furthermore, we describe foliation structures of these moduli spaces via level sets of Lyapunov-Reeb functions and develop algorithms for related problems.