The space of symmetric squares of hyperelliptic curves and integrable Hamiltonian polynomial systems on $\bbbR^4$

Abstract

We construct Lie algebras of vector fields on universal bundles $\mathcal{E}^2_{N,0}$ of symmetric squares of hyperelliptic curves of genus $g=1,2,\dots$, where $g=\left[\frac{N-1}{2}\right], \ N=3,4,\ldots$. For each of these Lie algebras, the Lie subalgebra of vertical fields has commuting generators, while the generators of the Lie subalgebra of projectable fields determines the canonical representation of the Lie subalgebra with generators $L_{2q}$, $q=-1, 0, 1, 2, \dots$, of the Witt algebra. We give explicitly a bi-rational equivalence of the space $\mathcal{E}^2_{N,0}$ and $\bbbC^{N+1}$ (in the case $N=5$ it is a well known result of Dubrovin and Novikov) and construct a polynomial Lie algebra on $\bbbC^{N+1}$, which contains two commuting generators. These commuting generators results in two compatible polynomial dynamical systems on $\bbbR^4$, which possess two common polynomial first integrals. Moreover, these systems are Hamiltonian and thus Liouville integrable. Using Abel-Jacobi two point map the solutions of these systems can be given in terms of functions defined on universal covering of the universal bundle of the Jacobians of the curves. These functions are not Abelian if $g\ne 2$. Finally we give explicit solutions of the constructed Hamiltonian systems on $\bbbR^4$ in the cases $N=3,4,5$.