The affine Tverberg theorem revisited

We prove the Bárány--Kalai--Tverberg conjecture extending the affine version of Tverberg's theorem to simplicial balls and polytopes other than the simplex: For any affine map $φ: P\to \mathbb R^d$ from a convex polytope $P$ of dimension $N=(d+1)(r-1)$ with $r\geq 2$, there exist $r$ pairwise disjoint faces $F_1,\ldots,F_r\subset\partial P$ such that $φ(F_1)\cap\dots\capφ(F_r)\neq\varnothing$. A similar statement holds for a simplicial ball $P$ with $φ$ assumed affine on all of its faces.