Published online by Cambridge University Press: 20 January 2009
We show that there is a pair of handlebodies H1 and H2 with common boundary F with the properties:
(a) There is no essential simple closed curve in F bounding a disc in both H1 and H2.
(b) Given any positive number, there are essential simple curves Cii = 1, 2 on F, bounding discs in Hi whose distance apart in the Hausdorff topology on F is less than this positive number.
Such an example has consequences for Heegaard splittings and recognising the 3-sphere.