A survey of the homology cobordism group

Abstract

In this survey, we present most recent highlights from the study of the homology cobordism group, with a particular emphasis on its long-standing and rich history in the context of smooth manifolds. Further, we list various results on its algebraic structure and discuss its crucial role in the development of low-dimensional topology. Also, we share a series of open problems about the behavior of homology $3$-spheres and the structure of ${\Theta }_{\mathbb{Z}}^3$. Finally, we briefly discuss the knot concordance group $\mathcal{C}$ and the rational homology cobordism group ${\Theta }_{\mathbb{Q}}^3$, focusing on their algebraic structures, relating them to ${\Theta }_{\mathbb{Z}}^3$, and highlighting several open problems. The appendix is a compilation of several constructions and presentations of homology $3$-spheres introduced by Brieskorn, Dehn, Gordon, Seifert, Siebenmann, and Waldhausen.

32 pages; 26 theorems (connecting several results) and 26 open problems (with different levels of difficulty)

References in corpus (2)

• Floer homology and knot complements
• Almost simple linear graphs, homology cobordism and connected Heegaard Floer homology

Cited by in corpus (4)

• Brieskorn spheres, cyclic group actions and the Milnor conjecture
• Unknotted Curves on Seifert Surfaces
• On the ${\Delta }_a$ invariants in non-perturbative complex Chern-Simons theory
• On homology planes and contractible $4$-manifolds