Browder-Livesay filtrations and the example of Cappell and Shaneson

TL;DR

This paper explores the use of Browder-Livesay filtrations to analyze nontrivial normal maps in 3-manifolds with quaternion fundamental groups, revealing new invariants and obstructions in surgery theory.

Contribution

It introduces a method to compute Browder-Livesay invariants for manifolds with quaternion fundamental groups, advancing understanding of surgery obstructions and their detection.

Findings

Proves that the third Browder-Livesay invariant vanishes for certain filtrations.

Computes splitting obstruction groups for subgroup inclusions of index 2.

Clarifies the structure of surgery obstruction groups for quaternion groups.

Abstract

Let $M^3$ be a 3-dimensional manifold with fundamental group $\pi_1(M)$ which contains a quaternion subgroup $Q$ of order 8. In 1979 Cappell and Shaneson constructed a nontrivial normal map $ f\colon M^3\times T^2\to M^3\times S^2$ which cannot be detected by simply connected surgery obstructions along submanifolds of codimension 0, 1, or 2, but it can be detected by the codimension 3 Kervaire-Arf invariant. The proof of non-triviality of $\sigma(f)\in L_5(\pi_1(M))$ is based on consideration of a Browder-Livesay filtration of a manifold $X$ with $\pi_1(X)\cong \pi_1(M)$. For a Browder-Livesay pair $Y^{n-1}\subset X^n$, the restriction of a normal map to the submanifold $Y$ is given by a partial multivalued map $\Gamma\colon L_n(\pi_1(X))\to L_{n-1}(\pi_1(Y))$, and the Browder-Livesay filtration provides an iteration $\Gamma^n$. This map is a basic step in the definition of the iterated Browder-Livesay invariants which give obstructions to realization of surgery obstructions by normal maps of closed manifolds. In the present paper we prove that $\Gamma^3(\sigma(f))=0$ for any Browder-Livesay filtration of a manifold $X^{4k+1}$ with $\pi_1(X)\cong Q$. We compute splitting obstruction groups for various inclusions $\rho\to Q$ of index 2, describe natural maps in the braids of exact sequences, and make more precise several results about surgery obstruction groups of the group $Q$.