Integrable Hierarchies and F-Manifolds with Compatible Connection

We study the geometry of integrable systems of hydrodynamic type of the form wt=X∘wx where ∘ is the product of a regular F-manifold. In the first part of the paper, we present a general construction of a connection compatible with the F-manifold structure starting from a frame of vector fields defining commuting flows of hydrodynamic type. In the second part of the paper, using this construction, we study regular F-manifolds with compatible connection and Euler vector field, (∇,∘,e,E), associated with integrable hierarchies obtained from the solutions of the equation d·dLa0=0 where L=E∘. In particular, we show that n-dimensional F-manifolds associated to regular operators L are classified by n arbitrary functions of a single variable. Moreover, we show that flat connections ∇ correspond to linear solutions a0.