Monodromy Groups and Self-Invariance

Abstract

Abstract For every polytope 𝒫 there is the universal regular polytope of the same rank as 𝒫 corresponding to the Coxeter group 𝒞 = [∞, … ,∞]. For a given automorphism d of 𝒞, using monodromy groups, we construct a combinatorial structure 𝒫d. When 𝒫d is a polytope isomorphic to 𝒫 we say that 𝒫 is self-invariant with respect to d, or d-invariant. We develop algebraic tools for investigating these operations on polytopes, and in particular give a criterion on the existence of a d-automorphismof a given order. As an application, we analyze properties of self-dual edge-transitive polyhedra and polyhedra with two flag-orbits. We investigate properties of medials of such polyhedra. Furthermore, we give an example of a self-dual equivelar polyhedron which contains no polarity (duality of order 2). We also extend the concept of Petrie dual to higher dimensions, and we show how it can be dealt with using self-invariance.