title: Optical Möbius strips, twisted ribbons, and the index theorem.
abstract: The twist numbers of circular optical Möbius strips and twisted ribbons are shown to obey the index theorem under rotation of the plane of observation, and under change in the radius of the path.
authors.affiliation: Physics Department, and Jack and Pearl Resnick Advanced Technology Institute, Bar-Ilan University, Ramat-Gan ISL52900, Israel. freund@mail.biu.ac.il
authors.forename: Isaac
authors.initials: I
authors.lastname: Freund