A note on non-thermodynamical applications of non-extensive statistics

It is pointed out that the constraint to be imposed to the maximization of the entropy for processes outside the class of thermodynamical systems, is generally not well defined. In fact, any probability distribution can be derived from Jaynes's principle with a suitable choice of the constraint. In the case of Tsallis's non-extensive formalism, this implies that it is not possible to establish any connection between specific non-thermodynamical processes and non-extensive mechanisms and, in particular, to assign any unambiguous non-extensivity index q to those processes.