The Effect of Explosive Divergence in a Coupled Map Lattice of Matrices
Total Page:16
File Type:pdf, Size:1020Kb
The Effect of Explosive Divergence in a Coupled Map Lattice of Matrices ∗ Guangqing Lu a, Rasa Smidtaite b,c, Zenonas Navickas b, Minvydas Ragulskis a,b, a School of Electrical and Information Engineering of Jinan University, 206 Qianshan Road, Zhuhai, Guangdong 519070, P.R. China b Centre of Nonlinear Systems, Kaunas University of Technology, Studentu 50-146, Kaunas LT-51368, Lithuania c Department of Applied Mathematics, Kaunas University of Technology, Studentu 50-318, Kaunas LT-51368, Lithuania a r t i c l e i n f o a b s t r a c t Article history: The extension of the Coupled map lattice (CML) model by replacing scalar nodal variables by matrix Received 16 April 2018 variables is investigated in this paper. The dynamics of the extended CML is investigated using formal Revised 11 June 2018 analytical and computational techniques. Necessary conditions for the occurrence of the effect of explo- Accepted 12 June 2018 sive divergence in the extended CML are derived. It is demonstrated that the extended CML can generate complex fractal patterns representing spatiotemporal divergence which can be controlled by the coupling Keywords: parameter between the nodes. The logistic map Coupled map lattices Kaneko model 1. Introduction plications in physics, cryptography, steganography, economics, bi- ology, etc. CMLs play an important role in image encryption The Logistic map is a paradigmatic model exhibiting chaotic be- algorithms [13–16] . Chaotic CML based stream ciphers are pro- havior [1]: posed by Li et al. [17] and Wang et al. [18] . CMLs are introduced to the market maker framework in order to investigate price changes ( + ) ( ) ( ) ( ) x t 1 = ax t (1 − x t ) ; t = 0 , 1 , 2 , . ; 0 ≤ a ≤ 4 ; 0 ≤ x 0 ≤ 1 . in a multi-market system [19] . A multiple phenotype predator– (1) prey model with mutation modelled via a CML [20] is proposed by Abernethy et al. CMLs are used to study neuronal dynamics [21] , A variety of extensions of the discrete logistic map has been coherence resonance phenomena [22] , and even stochastic reso- proposed during the last decades. The phase-modulated logistic nance on excitable small-world networks via a pacemaker [23] . map [2] is introduced by Nandi et al. Logistic map with a squared CMLs are also used as models for chaotic variations in spatiotem- sine perturbation [3] is presented by de Carvalho et al. Alternat- poral systems [24] . ing sign generalized logistic map with three parameters [4] is dis- CMLs exhibit a variety of spatiotemporal phenomena [25–32] . cussed by Sayed et al. Three bi- and tri-parameter generalized lo- Frozen random pattern, defect chaotic diffusion pattern, pattern gistic maps with arbitrary powers [5] are presented by Radwan. competition intermittency and fully developed turbulence in logis- Generalized fractional order logistic map suitable for pseudoran- tic map lattice with mixed linear-nonlinear couplings and its possi- dom number key generators [6] is presented by Ismail et al. Logis- ble applications in cryptography [25] are reviewed by Zhang. Two tic map in two dimensions is used to encrypt digital images [7– qualitative classes spatiotemporal intermittency and spatial inter- 9] . Chaotic encryption algorithm based on 3D logistic map [10] is mittency [26,27] are analyzed in the sine circle map lattice by proposed by Khade et al. Modified three-dimensional logistic map Jabeen et al. Sufficient conditions for synchronization of coupled is applied in steganography [11] . Symmetric image encryption maps on certain graphs [28] are derived Medvedev et al. An an- method based on intertwining logistic map [12] is proposed by Ye alytical study of traveling waves in CML [29,30] is developed by et al. Herrera et al. Properties of rotating pulse waves and oscillations Coupled map lattices are widely used to study the dynam- in a unidirectionally CML of ring structure [31] are discussed by ics of spatially extended logistic map systems. CMLs have ap- Horikawa. Method of adaptive control (based on the quasi sliding mode control design) of spatiotemporal chaos in CML [32] is pro- posed by Rahmani. ∗ Corresponding author at: Centre of Nonlinear Systems, Kaunas University of The main objective of this manuscript as well as necessary pre- Technology, Studentu 50-146, Kaunas LT-51368, Lithuania. liminary information is depicted in the following section. E-mail address: [email protected] (M. Ragulskis). 2. Preliminaries and motivation 2.4. Motivation 2.1. Idempotents and nilpotents The replacement of the scalar variable in the Logistic map by a second order square matrix yields unexpected and non-trivial phe- Let us consider such second order real matrices X ∈ R 2 × 2 that nomena (explosive divergence, temporary divergence, etc.) [33,34] . λ λ both eigenvalues of X (denoted as 1 , 2 ) are real. Note that X is A natural question is: what happens if scalar nodal variables in the not necessarily a symmetric matrix. CML nodes are replaced by matrix variables? In other words, this λ = λ = 1 − λ , = , ; = If 1 2 , then matrices Dk : λ −λ ( X l I); k l 1 2 k replacement increases the complexity of the spatially extended Lo- k l = gistic map at the nodes. How this increased complexity is repre- l are conjugate idempotents (I is the identity matrix): det Dk ; + = · = δ δ sented in the patterns generated by the lattice? The main objective 0 D1 D2 I; Dk Dl kl Dk ( kl is the Dirac delta function). Then X can be decomposed into the idempotent matrix form: of this paper is to seek answers to these questions. X = λ1 D 1 + λ2 D 2 (2) 3. The Coupled map lattice of matrices λ = λ = λ , = − λ = , If 1 2 0 then N : X 0 I is a nilpotent: det N 0 As stated previously, the main objective of this paper is to study 2 = N ( is a zero matrix). Then X can be expressed in the form a CML where scalar nodal variables x (t)( i ) are replaced by matrix of a nilpotent matrix: variables X ( t ) ( i ) ∈ R 2 × 2 : X = λ I + N . (3) ( + ) ( ) ε ( ) ( ) 0 X t 1 ( i ) = ( 1 − ε ) f (X t ( i ) ) + f (X t ( i + 1 ) ) + f (X t ( i − 1 ) ) 2 (7) 2.2. The Logistic map of matrices Further on, this model is entitled as the Coupled map lattice of The extension of the Logistic map [33] by replacing the scalar matrices (CMLM). variable x ( t ) by a second order square matrix variable X ( t ) is dis- cussed by Navickas et al. It is shown [33] that if the matrix of ini- 3.1. Idempotent matrices of initial conditions with identical tial conditions X (0) is an idempotent matrix, then the evolution of idempotents the Logistic map of matrices is described by two separate scalar Logistic maps of eigenvalues: Let us assume that all matrices of initial conditions are idem- potent matrices with the same idempotents D1 and D2 : (t +1 ) (t ) (t ) λ = aλ 1 − λ ; (0) ( 0 ) ( 0 ) 1 1 1 ( ) = λ ( ) + λ ( ) X i 1 i D1 2 i D2 (8) ( + ) ( ) ( ) (4) λ t 1 = λ t − λ t , 2 a 2 1 2 Note that ( ) ( ) ( 0 ) ( 0 ) ( 0 ) ( 0 ) ( 0 ) ( 0 ) 0 ( ) + 0 ( ) = λ ( ) + λ ( ) + λ ( ) + λ ( ) λ λ (0) X k X l 1 k 1 l D1 2 k 2 l D2 where 1 and 2 are two different distinct eigenvalues of X . In other words, the dynamics of the map is fully determined by (9) the initial eigenvalues and the parameter a . (0) ( ) ( ) ( 0 ) ( 0 ) ( 0 ) ( 0 ) However, if the matrix of initial conditions X is a nilpotent 0 ( ) 0 ( ) = λ ( )λ ( ) + λ ( )λ ( ) X k X l 1 k 1 l D1 2 k 2 l D2 (10) matrix, then the Logistic map of matrices can be divided into two Then, different scalar maps. The first one is a scalar Logistic map of the ( 0 ) ( ) ( ) ( ) λ (0) 0 = 0 − 0 eigenvalue ( 0 is the eigenvalue of X ). The other scalar map is f X ( i) aX ( i) I X ( i) μ( t ) μ(0) = the map incorporating the supplementary parameter ( ( 0 ) ( 0 ) ( 0 ) ( 0 ) = aλ ( i ) 1 − λ ( i ) D + aλ ( i ) 1 − λ ( i ) D , 1 ) [33] : 1 1 1 2 2 2 (11) ( + ) ( ) ( ) λ t 1 = λ t − λ t ; 0 a 0 1 0 (5) where I is the second order identity matrix. ( + ) ( ) (t ) μ t 1 = μ t − λ . Therefore, a 1 2 0 (1) ( 1 ) ( 1 ) X ( i ) = L ( i )D + L ( i )D (12) It is demonstrated [34] that the Logistic map of matrices can 1 1 2 2 exhibit the effect of explosive divergence if and only if the ma- where trix of initial conditions is a nilpotent matrix and the Lyapunov ex- ( 1 ) ( 1 ) ε ( 1 ) ( 1 ) ( ) = ( − ε )λ ( ) + λ ( + ) + λ ( − ) ; L1 i 1 1 i 2 1 i 1 1 i 1 ponent of the complementary scalar iterative map is greater than (13) ( 1 ) ( 1 ) ε ( 1 ) ( 1 ) zero. ( ) = ( − ε )λ ( ) + λ ( + ) + λ ( − ) , L2 i 1 2 i 2 2 i 1 2 i 1 ( ) ( ) λ 1 (s ) = f (λ 0 (s )) ; k = 1 , 2 ; s = 1 , . , n ; n is the number of k k 2.3. Coupled map lattices nodes in the CMLM with periodic boundary conditions ( (i − 1) = n when i = 1 ; (i + 1) = 1 when i = n ). The paradigmatic model of coupled map lattices is the Kaneko Thus, finally, model with periodic boundary conditions [35] : (t+1) (t +1 ) (t +1 ) X ( i ) = L ( i )D + L ( i )D (14) 1 1 2 2 ( + ) ( ) ε ( ) ( ) x t 1 ( i ) = ( 1 − ε ) f (x t ( i ) ) + f (x t ( i + 1 ) ) + f (x t ( i − 1 ) ) where 2 (t +1 ) (t ) ε (t ) (t ) (6) L ( i ) = ( 1 − ε ) f L ( i ) + f L ( i + 1 ) + f L ( i − 1 ) ; 1 1 2 1 1 (t +1 ) (t ) ε (t ) (t ) = , , .