Decision problems for two‑relator groups

Determine the decidability of the word problem, the conjugacy problem, and the isomorphism problem for finitely presented two‑relator groups.

Background

Unlike the one‑relator case (word problem solved by Magnus), the two‑relator setting lacks any general positive results: the core decision problems are unsolved. The authors emphasize that even finiteness classification is open, underscoring the gap between one‑ and two‑relator theories.

A resolution would be a major advance in combinatorial and geometric group theory.

References

The word problem, conjugacy problem, and isomorphism problem are all open for two-relator groups.

The theory of one-relator groups: history and recent progress (2501.18306 - Linton et al., 30 Jan 2025) in Section 8.4 (Two‑relator groups)