String-membrane duality in seven dimensions

The conjectured equivalence of the heterotic string to a K3 compactified type IIA superstring is combined with the conjectured equivalence of the latter to a compactified 11-dimensional supermembrane to derive a string membrane duality in seven dimensions; the membrane is a soliton of the string theory and vice versa. A prediction of this duality is that the heterotic string is a K3 compactification of the solitonic 11-dimensional fivebrane. It is verified that the worldsheet action of the D = 10 heterotic string is indeed obtainable by K3 compactification of the worldvolume action of the 11-dimensional fivebrane, and it is suggested how the worldvolume action of the D = 11 supermebrane may be similarly obtained by T3 compactification of the worldvolume action of a D = 10 heterotic fivebrane. Generalizations to D = 8 string-threebrane and membrane-membrane duality are also discussed.