On unions and intersections of nested families of cones (Q304554)

An indexed family of sets \(\{C_i:i\in I\}\) in \({\mathbb R}^n\) is \textit{nested} if for any pair of sets \(C_j,C_k\) in the family, either \(C_j\subset C_k\) or \(C_k\subset C_j\). In the paper under review the authors prove that the union and the intersection of a nested family of cones in \({\mathbb R}^n\) (not necessarily convex or having a common apex) are also cones.