Geometric obstructions for $ξ$-fillings of 3-manifolds
Daniel Galvin, Peter Teichner, Simona Veselá
TL;DR
This work develops a geometric obstruction theory for realizing a given normal 1-type $\xi$ on a closed 3-manifold as the boundary of a $\xi$-4-manifold. It introduces primary, secondary, and tertiary obstructions realized through geometric invariants derived from Wall's self-intersection concepts, refined to land in $H_1(\pi;\mathbb{Z}/2)$, and ties these to James spectral sequence differentials. The authors extend Kreck's modified surgery framework to describe when $\xi$-fillings exist and show that the vanishing of the geometric tertiary obstruction $\mathfrak{ter}^{geo}$ is equivalent to the existence of a $\xi$-filling, with a precise comparison to the algebraic tertiary invariant. Key ingredients include a non-orientable extension of the James spectral sequence, refined intersection invariants $\mu_J$ and $\lambda_J$, and secondary Wu-type formulas, culminating in a complete obstruction theory for null-bordism in this setting. The results connect 3-manifold fillability to 4-manifold bordism through explicit geometric constructions and offer a framework for understanding higher-stage obstructions in the $\xi$-bordism context.
Abstract
We consider the realisation problem for normal 1-types of 4-manifolds with a given boundary. More precisely, given a normal 1-type $ξ$ and closed 3-dimensional $ξ$-manifold $Y$, does there exist a compact 4-dimensional $ξ$-manifold with boundary $Y$? We describe a three stage obstruction theory for the existence of such a 4-manifold, with our main contribution being a `tertiary' obstruction that we describe geometrically via Wall's quadratic self-intersection form.
