Triple linking numbers and surface systems

TL;DR

This paper introduces a refined invariant for triple linking numbers of links in the 3-sphere, establishing conditions under which links share this invariant and relating it to surface systems and group quotients.

Contribution

It provides a new refined value group for triple linking numbers and characterizes when two links have the same collection based on surface systems and group isomorphisms.

Findings

Same refined triple linking number collection implies homeomorphic surface systems.

Links with the same pairwise linking numbers and surface systems are bordant over $B \\mathbb{Z}^n$.

Isomorphism of certain lower central series quotients of link groups preserves meridians and longitudes.

Abstract

We give a refined value group for the collection of triple linking numbers of links in the 3-sphere. Given two links with the same pairwise linking numbers we show that they have the same refined triple linking number collection if and only if the links admit homeomorphic surface systems. Moreover these two conditions hold if and only if the link exteriors are bordant over $B \mathbb{Z}^n$, and if and only if the third lower central series quotients $\pi/\pi_3$ of the link groups are isomorphic preserving meridians and longitudes. We also show that these conditions imply that the link groups have isomorphic fourth lower central series quotients $\pi/\pi_4$, preserving meridians.