The equivalence between two real Seiberg-Witten homologies
Yonghan Xiao
TL;DR
This work establishes a rigorous isomorphism between the real monopole Floer homology ${\mathrm{HMR}}$ and the real Seiberg–Witten Floer homotopy type ${\mathrm{SWF}}_{\mathbb{Z}_2}$ for real rational homology spheres with compatible real spin^c structures, unifying two parallel real-structure approaches to Seiberg–Witten invariants. The proof adapts the finite-dimensional Morse framework to the real setting by working in the global Coulomb slice, developing real Hessians, and constructing a perturbation theory that respects the ${\mathbb{Z}}_2$-action, then relating finite- and infinite-dimensional Morse theories via a sequence of intermediate complexes. It also yields corollaries including Frøyshov-type invariants and Smith-type inequalities, and identifies the $v$-action on both sides, providing real analogues of classical localization phenomena. The results solidify the compatibility between gauge-theoretic invariants on real three-manifolds and their homotopy-type counterparts, with implications for real L-spaces and branched-cover knot theory. Overall, the paper extends the Hitchin–Friedman–Manolescu program to the real setting, offering tools for comparing real Floer-type invariants across different formalisms and enabling new constraints in real three-manifold topology.
Abstract
We show that for a real rational homology sphere $Y$ equipped with a real $\mathrm{spin^c}$ structure $\s$, the real monopole Floer homology defined by Li and the real Seiberg-Witten Floer homology defined by Konno, Miyazawa and Taniguchi are isomorphic. As corollaries, we identify some Frøyshov-type invariants and prove two Smith-type inequalities.
