I've read that the exponential behavior predicted in e.g. RC circuits by taking the Laplace-domain impedance of capacitors to be 1/sC leads to a causality violation, and that after much testing of many capacitors some guys named Westerlund and Eklam determined that the true behavior is a probably a power law, which I guess means the dv/dt in I = C dv/dt would actually have to be some kind of fractional derivative.
Can anyone elaborate on why this is so?