A necessary and sufficient condition for $k$-transversals
A necessary and sufficient condition for $k$-transversals
We establish a necessary and sufficient condition for a family of convex sets in $\mathbb{R}^d$ to admit a $k$-transversal, for any $0 \le k \le d-1$. This result is a common generalization of Helly's theorem ($k=0$) and the Goodman-Pollack-Wenger theorem ($k=d-1$). Additionally, we obtain an analogue in the complex setting …