“…This is in stark contrast to the case of Minkowski valuations intertwining only rigid motions which form an infinite dimensional cone. Nonetheless, also here substantial inroads towards a complete classification have been made (see [26,54,57,59,60]), making it possible to extend affine inequalities for the projection body operator by Lutwak [38] to a much larger class of Minkowski valuations (see [1,4,6,49,56,57]). This raised the natural problem whether the Petty projection inequality also holds in greater generality.…”