BPS quivers of five-dimensional SCFTs, Topological Strings and q-Painlev\'e equations

We study the discrete flows generated by the symmetry group of the BPS quivers for Calabi-Yau geometries describing five dimensional superconformal quantum field theories on a circle. These flows naturally describe the BPS particle spectrum of such theories and at the same time generate bilinear equations of q-difference type which, in the rank one case, are q-Painlev'e equations. The solutions of these equations are shown to be given by grand canonical topological string partition functions which we identify with $\tau$-functions of the cluster algebra associated to the quiver. We exemplify our construction in the case corresponding to five dimensional $SU(2)$ pure Super Yang-Mills and $N_f=2$ on a circle.