“…We are led to a Casimir piston model in which spacetime is flat. This model has attracted considerable attention in the recent literature [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]. One reason for the current interest is obviously the mathematical elegance of the formalism; the efficiency of regularization procedures like the zeta function regularization is quite striking.…”