Renormalization group analysis: continuous medium with dominating diffusive coupling

If we search a sulution of the operator renormapization group equation Gk+1[x]=SGk[Gk[S-1x]] as Gk[x]=G[x]+Hk[x], where ||H||<<1 and G is a fixed point of the operator equation, we can find that the operators H obey the iterative relation

wherw G' is the Frechet derivative. Setting Hk~nk, we arrive to the eigenvalue problem for the operator equation
In a class of perturbations preserving the translational invariance of the evolution operators the following eigenvalues are found.

Relevant eigenvalues

Variation of the control parameter of individual cells without a modification of coupling between the cells

Anti-symmetric inertial coupling

Anti-symmetric dissipative coupling (advection)

Symmetric inertial coupling

Irrelevant eigenvalues

Symmetric dissipative coupling (diffusion)

It may be concluded that in a one-dimensional lattice constructed of cells with dominating symmetric dissipative (diffusive) coupling the following properties of universality and scaling must be valid.

Universality. Evolution operator ofer 2k time steps in asymptotic of large k is determined (up to scale changes) by four parameters. They are the control parameter of individual cells l and three parameters of coupling: anti-symmetric inertial a, anti-symmetric dissipative b, symmetric inertial g.

Scaling. Being given a definite regime of spatio-temporal dynamics at some parameter set (l, a, b, g) we have to observe similar dynamics at lnew=lc+(llс)/d, anew=a/n1, bnew=b/n2, gnew=g/n3 with appropriate initial conditions (rescaling by a). In the last case a characteristic time scale grows by 2 times, and a spatial scale by 21/2 раза.

Let us consider examples of model equations and illustrations of scaling for the coupled map lattices. We suppose that there is strong diffusion and a weak additional coupling of one of the mentioned three types. A system length is assumed to be sufficiently large to exclude dependence of bifurcation parameters on the system size.

Diffusion and anti-symmetric inertial couplig

Let us consider a model of coupled map lattice



with boundary conditions x(0)=0, x(M)=0. Here the simmetric dissipative coupling, or diffusion, is represented by operator L and the anti-symmatric inertial coupling is characterized by parametera. The top figure to the right is the chart of regimes in the plane of coupling parameter a and control parameter l. Color areas designate states that are approximately uniform in space in central region of the medium. Colors code time periods (inicated by numbers 1, 2, 4, 8). The gray area corresponds to appearance of non-uniform states, travelling regular or chaotic waves. Note self-similarity of the chart: near the critical point a=0, l=lс the parameter plane arrangement repeats itself in smaller scales, and the scaling factors along the vertical and horizontal axes are d=4.6692 and n2=1.7698, respectively.

Diffusion and anti-symmetric dissipative coupling связь

Let us consider now a lattice with evolution operator that is factorizable as in the case of the diffusion coupling, but asymmetric


with boundary conditions x(0)=x*, x(m)=x*, where x* - is the fixed point of an individual map. Beside the pure diffusion we have here anti-symmetric dissipative coupling characterized by parameter b. The top picture to the left is the chart of regimes in the parameter plane (b,l). Color areas designate states that are approximately uniform in space in central region of the medium. Colors code time periods (inicated by numbers 1, 2, 4, 8). The gray area corresponds to appearance of non-uniform states, travelling regular or chaotic waves. Near the critical point b=0, l=lс the chart of regimes manifests scaling property, with factors d=4.6692 and n2=1.4142 along vertical and horizontal axes, respectively.

Diffusion and symmetric inertial coupling

Let us consider a coupled map lattice

,

with boundary conditions of periodicity x(0)=x(M). Beside the diffusion (operator L) here the symmetric inertial coupling is present (parameter g). The chart of regimes in the parameter plane (g, l) is shown, the color areas correspond to states that are approximately uniform in in central region of the medium. Colors code time periods (inicated by numbers 1, 2, 4, 8). The gray area corresponds to appearance of non-uniform states, Turing-like structures. Near the critical point g=0, l=lс the picture reproduces itself in smaller scales, and the scaling factors are d=4.6692 for vertical and n3=-1.2514 for horizontal axis.

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Coupled map lattices
Coupled maps: Two types of coupling
Two coupled maps: Renormalization group analysis
Coupled map lattice: Lattice scaling
From lattice to continuous medium
Medium with different types of coupling
Globally coupled maps
Coupled map lattices and real physical systems

Saratov group
of theoretical nonlinear
dynamics
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