Contractible open 3-manifolds which non-trivially cover only non-compact 3-manifolds
arXiv:math/9606225
Abstract
Suppose is a closed, connected, orientable, \irr\ \3m\ such that is infinite. One consequence of Thurston's geometrization conjecture is that the universal covering space of must be \homeo\ to $\RRR$. This has been verified directly under several different additional assumptions on . (See, for example, \cite{2}, \cite{3}, \cite{6}, \cite{19}.)