Foliations on the moduli space of rank two connections on the projective line minus four points

We look at natural foliations on the Painlevé VI moduli space of regular connections of rank $2$ on $\pp ^1 -\{ t_1,t_2,t_3,t_4\}$. These foliations are fibrations, and are interpreted in terms of the nonabelian Hodge filtration, giving a proof of the nonabelian Hodge foliation conjecture in this case. Two basic kinds of fibrations arise: from apparent singularities, and from quasiparabolic bundles. We show that these are transverse. Okamoto's additional symmetry, which may be seen as Katz's middle convolution, exchanges the quasiparabolic and apparent-singularity foliations