Published online by Cambridge University Press: 08 November 2018
We show that the bar version of the $\text{Pin}(2)$-monopole Floer homology of a three-manifold
$Y$ equipped with a self-conjugate spin
$^{c}$ structure
$\mathfrak{s}$ is determined by the triple cup product of
$Y$ together with the Rokhlin invariants of the spin structures inducing
$\mathfrak{s}$. This is a manifestation of mod
$2$ index theory and can be interpreted as a three-dimensional counterpart of Atiyah’s classical results regarding spin structures on Riemann surfaces.