On an extension problem on the moment curve

Abstract: We show that for $2\le d\le 4$, every finite geometric simplicial complex $Δ$ in $\mathbb{R}^d$ with vertices on the moment curve can be extended to a triangulation $T$ of the cyclic polytope $C$ where $Δ, T$ and $C$ all have the same vertex set. Further, for $d\ge 5$ we construct for every $n\ge d+3$ complexes $Δ$ on $n$ vertices for which no such triangulations $T$ exist. Our result for $d=4$ has the following novel algebraic application, due to a correspondence by Oppermann and Thomas (JEMS, 2012): every maximal rigid object in $\mathcal{O}{A_n^{2}}$ is cluster tilting, where $\mathcal{O}{A_n^δ}$ denotes a higher dimensional cluster category introduced by Oppermann and Thomas for $A_n^δ$, where $A_n^δ$ denotes a higher Auslander algebra of linearly oriented type $A$.