Circle-valued Morse theory
In mathematics, circle-valued Morse theory studies the topology of a smooth manifold by analyzing the critical points of smooth maps from the manifold to the circle, in the framework of Morse homology.[1] It is an important special case of Sergei Novikov's Morse theory of closed one-forms.[2]
Michael Hutchings and Yi-Jen Lee have connected it to Reidemeister torsion and Seiberg–Witten theory.[3]