Waist size for cusps in hyperbolic 3-manifolds

The waist size of a cusp in an orientable hyperbolic 3-manifold is the length of the shortest nontrivial curve in the maximal cusp boundary generated by a parabolic isometry. A variety of results on waist size are proved. In particular, it is shown that the smallest possible waist size, which is 1, is realized only by the cusp in the figure-eight knot complement.