Vertex Dismissibility and Scalability of Simplicial Complexes

Abstract: We introduce vertex dismissible and scalable simplicial complexes, generalizing the classical notions of vertex decomposability and shellability. We prove that a complex satisfies these properties if and only if its initial dimension skeleton is vertex decomposable or shellable, respectively. Algebraically, we define vertex divisible ideals and ideals with degree quotients, proving they are the exact Alexander duals of these complexes. This establishes a corresponding topological and homological hierarchy that interpolates between classical structural properties and the initially Cohen-Macaulay condition. Furthermore, we demonstrate that for complexes of initial dimension one and the independence complexes of co-chordal and cycle graphs, vertex dismissibility, scalability, and initial Cohen-Macaulayness are equivalent to weak connectedness. Finally, we provide a complete skeletal characterization of these properties, a generalized perspective that recovers numerous classical theorems as immediate consequences.