Rigorous posts don't get no props. My previous attemptedly rigorous post on the subject was just to say, I guess opaquely, that it seems to capture the essence of a stable arrangement — like one forced by an elastic collar — to merely require: any sufficiently small perturbation of the arrangement (modify the centers but not the radii) cannot decrease the *diameter* of the arrangement (= the diameter of the smallest disk containing all disks of the arrangement). It seems clear that a rosette of 7 equal disks, but with the central one removed, is stable in this sense (despite the hole). —Dan ----- On 4/23/19, Allan Wechsler <acwacw@gmail.com> wrote:
I don't mind any particular model, but I think I just don't understand the no-slip condition. Can you rigorize it?