Skip to main content
1 of 3
Sam Nead
  • 28.1k
  • 5
  • 72
  • 131

Here is a first counter-example.

Suppose that $V$ is a genus two handlebody of dimension three. For example, $V$ can be obtained by embedding a “eye-glasses” graph in three-space and taking a small regular neighbourhood. Let $M$ be the double of $V$ across its boundary. That is, we take two copies of $V$ and glue via the identity on the boundary.

The universal cover of $M$ is a copy of the three-sphere, minus a Cantor set.

Sam Nead
  • 28.1k
  • 5
  • 72
  • 131