The Pontrjagin Dual of 4-Dimensional Spin Bordism

Understand

The goal of this paper is to study the Pontrjagin dual of (reduced) 4-dimensional Spin bordism.

• That is to say, we consider the functor from the category of topological spaces to the category of compact abelian groups that associates to each space X the compact group of homomorphisms from the reduced 4-dimensional Spin bordism of X to the circle.
• In a previous paper, we studied the analogous problem for 3-dimensional Spin bordism.
• Our work was motivated by some questions from physics.