Low dimensional bihamiltonian structures of topological type

We construct local bihamiltonian structures from classical $W$-algebras associated to non-regular nilpotent elements of regular semisimple type in Lie algebras of type $A_2$ and $A_3$. They form exact Poisson pencil, admit a dispersionless limit and their leading terms define logarithmic or trivial Dubrovin-Frobenius manifolds. We calculate the corresponding central invariants which are expected to be constants. In particular, we get Dubrovin- Frobenius manifolds associated to the focused Schrödinger equation and Hurwitz space $M_{0;1,0}$ and the corresponding bihamiltonian structures of topological type.