Doubly slicing knots and embedding 3-manifolds in 4-manifolds
Se-Goo Kim, Taehee Kim
TL;DR
This work extends the double slice theory by defining the $X$-double slice genus $g_{ds}^X(K)$ for knots in $S^3$ relative to a simply connected 4-manifold $X$, and develops a network of obstructions based on $H_1$-embeddings and $\rho^{(2)}$-invariants. The authors prove that $g_{ds}^X(K)$ can be arbitrarily large for any fixed $X$, even when $K$ is algebraically doubly slice or when all prime-power branched covers embed into $S^4$ and Casson–Gordon obstructions vanish. They relate genus bounds to $H_1$-embedding obstructions, extend the stabilizing and superslice notions to $X$-contexts, and define the $X$-double stabilizing number and $X$-superslice genus, proving they can be made arbitrarily large and establishing several tight inequalities. Together, these results illuminate the intricate landscape of how 3-manifolds bound, embed, and interact with 4-manifold topology through generalized slice and stabilizing invariants, with potential implications for understanding knotted surfaces in higher dimensions.
Abstract
For a knot $K$ in the 3-sphere and a simply connected closed 4-manifold $X$, we define the $X$-double slice genus of $K$, extending the notion from the case when $X$ is the 4-sphere. We show that for each integer $n$, there exists an algebraically doubly slice and ribbon knot $K$ whose $X$-double slice genus is greater than $n$. Our arguments use new $L^2$-signature obstructions to embedding closed 3-manifolds with infinite cyclic first homology into closed 4-manifolds with infinite cyclic fundamental group, in a way that preserves first homology. We also extend the concept of the superslice genus of a knot to simply connected 4-manifolds and show that there exist doubly slice knots whose generalized superslice genera are arbitrarily large. Furthermore, we define the double stabilizing number of a knot, extending the stabilizing number introduced by Conway and Nagel, and show that this invariant can also be arbitrarily large.
