Minimal Face Numbers for Volume Rigidity
Given a pure d-dimensional simplicial complex embedded in Rd, we may measure the volumes of its maximal simplices. We say such an embedding is d-volume rigid if the only continuous deformations of its vertices are images of the whole complex under a d-volume preserving transformation, and that the simplicial complex is d-volume rigid if a typical embedding of it is d-volume rigid. In Euclidean bar-joint rigidity, Maxwell counts provide the least number of edges required for rigidity in Rd in terms of d and the number of vertices. In a similar spirit, we provide the least number of k-simplices, for all 0≤k≤d, required for a complex to be d-volume rigid in terms of d and the number of vertices. We use recent applications of algebraic combinatorics to the volume rigidity problem, as well as what is known about the volume rigidity matroid.