The unknotting number and classical invariants II

Maciej Borodzik, Stefan Friedl

Published 2012-07-10, updated 2013-08-02Version 2

In [BF12] the authors associated to a knot K an invariant n_R(K) which is defined using the Blanchfield form and which gives a lower bound on the unknotting number. In this paper we express n_R(K) in terms of Levine-Tristram signatures and nullities of K. In the proof we also show that the Blanchfield form with real coefficients is diagonalizable.