Published online by Cambridge University Press: 24 October 2008
Given an embedding of an oriented surface F in an oriented three-manifold M and a homeomorphism h of F, one can construct another three-manifold Mn by cutting M along F and re-glueing the two boundary components using h. Let F be a genus two surface and r the involution which exhibits F as the 2-fold branched cover of S2 branched over six points. In this special case we call Mr the mutation of M along F.