Initial value space of the four dimensional Painlevé system with $(A_5+A_1)^{(1)}$ symmetry
Kazuya Matsugashita, Takao Suzuki
TL;DR
This work extends the Okamoto program to a four-dimensional Painlevé-type system with $(A_5+A_1)^{(1)}$ symmetry by constructing a holomorphic, symplectic initial value space. The authors build a Hirzebruch-type compactification $\,\Sigma_ta$ and identify accessible singularities, then resolve them through a sequence of blow-ups (for $C^0$) and formal power-series methods (for $P^0$), aided by the system’s birational symmetries. The resolution yields a smooth initial value space $E$, assembled from 33 coordinate charts, on which the dynamics is governed by a unique degree-5 polynomial Hamiltonian in $(q_1,q_2,p_1,p_2)$. This provides a geometric IVS for the four-dimensional Painlevé system, consistent with Sakai’s classification and extending known results about holomorphy and symmetries in higher dimensions.
Abstract
The initial value spaces of the Painlevé equations are proposed by Okamoto. They are symplectic manifolds in which the Painlevé equations are described as polynomial Hamiltonian systems on all coordinates. In this article, we construct an initial value space of the four dimensional Painlevé system with affine Weyl group symmetry of type $(A_5+A_1)^{(1)}$.
