entropy-18-00160
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Entropy 2016, <strong>18</strong>, 160 15 of 20<br />
identified with dt, i.e., δt ≡ dt, and consequently, it will be considered as an independent variable.<br />
We reserve the notation dt for the usual time as in the Hamiltonian complex system dynamics.<br />
3. The complex system dynamics is described through fractal variables, i.e., functions depending<br />
on both the space-time coordinates and the scale resolution, since the differential time reflection<br />
invariance of any dynamical variable is broken. Then, in any point of the fractal curve,<br />
two derivatives of the variable field Q(t, dt) can be defined:<br />
d + Q (t, dt)<br />
dt<br />
d − Q (t, dt)<br />
dt<br />
= lim<br />
∆t→0 +<br />
Q (t + ∆t, ∆t) − Q (t, ∆t)<br />
∆t<br />
= lim<br />
∆t→0 −<br />
Q (t, ∆t) − Q (t − ∆t, ∆t)<br />
∆t<br />
(A1)<br />
The “+” sign corresponds to the forward process, while the “−“ sign correspond to the<br />
backwards one.<br />
4. The differential of the spatial coordinate field dX i (t, dt)is expressed as the sum of the<br />
two differentials, one of them being scale resolution independent (differential part d ± x i (t))<br />
and the other one being scale resolution dependent (fractal part d ± ξ i (t)) [6,7], i.e.,<br />
d ± X i (t, dt) = d ± x i (t) + d ± ξ i (t, dt)<br />
(A2)<br />
5. The non-differentiable part of the spatial coordinate field satisfies the fractal equation [6,7]:<br />
d ± ξ i (t, dt) = λ i ± (dt) 1/D F<br />
(A3)<br />
where λ i ± are constant coefficients through which the fractalization type is specified and D F<br />
defines the fractal dimension of the fractal curve.<br />
In our opinion, the processes in complex systems imply a dynamics on geodesics having various<br />
fractal dimensions. Precisely, for D F = 2, quantum-type processes are generated. For D F < 2,<br />
correlative-type processes are induced, while for D F > 2, non-correlative-type ones can be found<br />
(for details, see [6–9,13]).<br />
6. The differential time reflection invariance of any dynamical variable is recovered by combining<br />
the derivatives d +<br />
/<br />
dt and d−<br />
/<br />
dt in the non-differentiable operator:<br />
dˆ<br />
dt = 1 2<br />
(<br />
d+ + d −<br />
dt<br />
)<br />
− i 2<br />
( )<br />
d+ − d −<br />
This is a natural result of the complex prolongation procedure [7]. Applying now the<br />
non-differentiable operator to the spatial coordinate field yields the complex velocity field:<br />
ˆV i = ˆ dX i<br />
dt<br />
dt<br />
(A4)<br />
= V i D − Vi F (A5)<br />
with:<br />
VD i = 1 ( )<br />
v i + + v i − , VF i 2<br />
= 1 ( )<br />
v i + − v i −<br />
2<br />
v i + = d +x i + d + ξ i<br />
, v i − = d −x i + d − ξ i<br />
dt<br />
dt<br />
(A6)<br />
The real part VD i is differentiable and scale resolution independent (differentiable velocity<br />
field), while the imaginary one VF i is non-differentiable and scale resolution dependent (fractal<br />
velocity field).<br />
7. In the absence of any external constraint, an infinite number of fractal curves (geodesics) can<br />
be found relating any pair of points, and this is true on all scales. Then, in the fractal space,