File:Quasi-periodic attractor of Langford equation.png

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English: Quasi-periodic attractor of Langford equation

The used parameters are (α, β, λ, ω, ρ, ε) = (1, 0.7, 0.6, 3.5, 0.25, 0). Thee orbits in red, blue, and green starts from different initial values, and they are attracted to a 2-dimentional torus. References for making this figure are as follows:

  • 徳永 隆治 (1990) "カオスとフラクタル" in カオス ―カオス理論の基礎と応用, Information & Computing 49 (初版 ed.), サイエンス社, p. 70 ISBN: 4-7819-0592-7.
  • 池口 徹・山田 泰司・小室 元政 (2000) 合原 一幸 , ed. カオス時系列解析の基礎と応用 (初版 ed.), 産業図書, p. 50 ISBN: 978-4-7828-1010-1.

The following is the original source by Langford:

  • Langford W.F. (1984) Numerical Studies of Torus Bifurcations. In: Küpper T., Mittelmann H.D., Weber H. (eds) Numerical Methods for Bifurcation Problems. International Series of Numerical Mathematics / Internationale Schriftenreihe zur Numerischen Mathematik / Série internationale d’Analyse numérique, vol 70. Birkhäuser, Basel. https://doi.org/10.1007/978-3-0348-6256-1_19
Date
Source Own work
Author Yapparina

Scilab source

clear;

//Parameters
alpha = 1;
beta = 0.7;
lambda = 0.6;
omega = 3.5;
rho = 0.25;
epsilon = 0;

// x=x(1), y=x(2), z=x(3) 
function dx = LANGFORD(t,x)
  dx(1) = (x(3) - beta) * x(1) - omega * x(2) ;
  dx(2) = omega * x(1) + (x(3) - beta) * x(2) ; 
  dx(3) = lambda + alpha * x(3) - x(3)^3/3 - (x(1)^2 + x(2)^2) * (1 + rho * x(3)) + epsilon * x(3) * x(1)^3 ; 
endfunction

// The time range and step for calculation
Tin = 0;
Tout = 70;
Tstep = 0.01;
t = Tin:Tstep:Tout;

// The initial values and ode solvers for 3 cases
x10 = -0.5;
y10 = -0.5;
z10 = 2.5;
X10 = [x10; y10; z10];

X1 = ode(X10,0,t,LANGFORD);

x20 = 0.3;
y20 = 0.3;
z20 = 2.4;
X20 = [x20; y20; z20];

X2 = ode(X20,0,t,LANGFORD);

x30 = 0.6;
y30 = -0.6;
z30 = 2.3;
X30 = [x30; y30; z30];

X3 = ode(X30,0,t,LANGFORD);

clf;

param3d(X1(1,:), X1(2,:), X1(3,:), 'r')
e=gce()
e.foreground=color('red');

param3d(X2(1,:), X2(2,:), X2(3,:), 'r')
h=gce()
h.foreground=color('blue');

param3d(X3(1,:), X3(2,:), X3(3,:), 'r')
h=gce()
h.foreground=color('green');

xlabel('x')
ylabel('y')
zlabel('z')

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