Hedge duality and the Evans function

Two generalisations of the Evans function, for the analysis of the linearis ation about solitary waves, are shown to be equivalent. The generalisation introduced by Alexander, Gardner and Jones [J. reine Angew. Math. 410 (1990 ) 167] is based on exterior algebra and the generalisation introduced by Sw inton [Phys. Lett. A 163 (1992) 57] is based on a matrix formulation and ad joint systems. In regions of the complex plane where both formulations are defined, the equivalence is geometric: we show that the formulations are du al and the duality can be made explicit using Hedge duality and the Hedge s tar operator. Swinton's formulation excludes potential branch points at whi ch the Alexander, Gardner and Jones formulation is well-defined. Therefore we consider the implications of equivalence on the analytic continuation of the two formulations. (C) 1999 Published by Elsevier Science B.V.