Deformation classes of invertible field theories and the Freed--Hopkins conjecture

Abstract

We prove a conjecture of Freed and Hopkins, which relates deformation classes of reflection positive, invertible, $d$-dimensional extended field theories with fixed symmetry type to a certain generalized cohomology of a Thom spectrum. Along the way, we establish several results, including the construction of a smooth variant of the Brown--Comenetz dual of the sphere spectrum and a calculation of the "deformation type" of the extended geometric bordism category.