Some 3-manifolds and 3-orbifolds with large fundamental group
Some 3-manifolds and 3-orbifolds with large fundamental group
We provide two new proofs of a theorem of Cooper, Long and Reid which asserts that, apart from an explicit finite list of exceptional manifolds, any compact orientable irreducible 3-manifold with non-empty boundary has large fundamental group. The first proof is direct and topological; the second is group-theoretic. These techniques …