Dubrovin's duality for F-manifolds with eventual identities

A vector field E on an F-manifold (M,∘,e) is an eventual identity if it is invertible and the multiplication X⁎Y:=X∘Y∘E−1 defines a new F-manifold structure on M. We give a characterization of such eventual identities, this being a problem raised by Manin (2005) [12]. We develop a duality between F-manifolds with eventual identities and we show that this duality is compatible with the local irreducible decomposition of F-manifolds and preserves the class of Riemannian F-manifolds. We find necessary and sufficient conditions on the eventual identity which ensure that the classes of harmonic Higgs bundles, DChk-structures and weak CV-structures are preserved by our duality. Examples of such structures are given in the case of a semi-simple multiplication. We use eventual identities to construct compatible pairs of metrics.