On bodies in ${\mathbb{R}}^5$ with directly congruent projections or sections

Abstract

Let $K$ and $L$ be two convex bodies in ${\mathbb{R}}^5$ with countably many diameters, such that their projections onto all 4 dimensional subspaces containing one fixed diameter are directly congruent. We show that if these projections have no rotational symmetries, and the projections of $K,L$ on certain 3 dimensional subspaces have no symmetries, then $K=\pm L$ up to a translation. We also prove the corresponding result for sections of star bodies.