Substitution Rules for Higher-Dimensional Paperfolding Structures

We present a general scheme how to construct a substitution rule for generating $d$-dimensional analogues of the paperfolding structures. This substitution is proven to be primitive, so that the translation action on the hull forms a strictly ergodic dynamical system. The substitution admits a coincidence in the sense of Dekking, which implies that the dynamical system has pure point spectrum. The same then holds true also for the diffraction spectrum. The substitution also allows us to give estimates on the complexity of the paperfolding structures, and to determine topological invariants like the \v{C}ech cohomology groups of the hull for dimensions $d\le 2$.