Finite invariant sets with bridging points in logistic IFS

We investigate iterated function systems that randomly alternate between two non-identical one-dimensional maps as simple models of regime-switching dynamical systems. Our primary focus is on finite invariant sets exhibiting “toss-and-catch” dynamics, in which trajectories alternate between fixed points and periodic points of the constituent maps. Using two representative types of low-dimensional nonlinear systems—a pair of logistic maps and a combination of logistic and tent maps—we derive exact parameter conditions for several toss-and-catch structures. The comparison between these systems reveals two distinct mechanisms for finite invariant sets: one mediated by “bridging points” that connect invariant structures of different maps, and another generated by nontrivial intersections shared by the maps themselves. Notably, we identify invariant sets containing bridging points that are not periodic points of either constituent map. These results demonstrate that switching between simple nonlinear maps can generate invariant structures that do not exist in the constituent systems alone, suggesting a more general mechanism for the emergence of invariant structures in random dynamical systems.