Composition law for the Cole-Cole relaxation and ensuing evolution equations

Publication date: Available online 15 March 2019Source: Physics Letters AAuthor(s): K. Górska, A. Horzela, A. LattanziAbstractPhysically natural assumption says that any relaxation process taking place in the time interval [t0,t2], t2>t0≥0 may be represented as a composition of processes taking place during time intervals [t0,t1] and [t1,t2] where t1 is an arbitrary instant of time such that t0≤t1≤t2. For the Debye relaxation such a composition is realized by usual multiplication which claim is not valid any longer for more advanced models of relaxation processes. We investigate the composition law required to be satisfied by the Cole-Cole relaxation and find its explicit form given by an integro-differential relation playing the role of the time evolution equation. The latter leads to differential equations involving fractional derivatives, either of the Caputo or the Riemann-Liouville senses, which are equivalent to the special case of the fractional Fokker-Planck equation satisfied by the Mittag-Leffler function known to describe the Cole-Cole relaxation in the time domain.

Source: Physics Letters A - March 16, 2019 Category: Physics Source Type: research