Spin structures and superstrings

Abstract: In superstring theory spin structures are present on both the 2-dimensional worldsheet and 10-dimensional spacetime. We present a new proposal for the B-field in superstring theory and demonstrate its interaction with worldsheet spin structures. Our formulation generalizes to orientifolds, where various twistings appear. A special case of the orientifold worldsheet B-field amplitude is a KO-theoretic construction of the Z/8Z-valued Kervaire invariant on pin-minus surfaces.