# Lorenz attractor

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Lorenz_system_r28_s10_b2-6666.png
A plot of the trajectory Lorentz system for values r=28, σ = 10, b = 8/3

The Lorenz attractor, introduced by Edward Lorenz in 1963, is a non-linear three-dimensional deterministic dynamical system derived from the simplified equations of convection rolls arising in the dynamical equations of the atmosphere. For a certain set of parameters the system exhibits chaotic behavior and displays what is today called a strange attractor; this was proven by W. Tucker in 2001. The strange attractor in this case is a fractal of Hausdorff dimension between 2 and 3. Grassberger (1983) has estimated the Hausfdorff dimension to be 2.06 ± 0.01 and the correlation dimension to be 2.05 ± 0.01.

The system arises in lasers, dynamos, and specific waterwheels (http://www.zeuscat.com/andrew/chaos/lorenz.html).

[itex]\frac{dx}{dt} = \sigma (y - x)[itex]
[itex]\frac{dy}{dt} = x (r - z) - y[itex]
[itex]\frac{dz}{dt} = xy - b z[itex]

where [itex]\sigma[itex] is called the Prandtl number and r is called the Reynolds number. [itex]\sigma,r,b>0[itex], but usually [itex]\sigma=10[itex], [itex]b=8/3[itex] and r is varied. The system exhibits chaotic behavior for r = 28 but displays knotted periodic orbits for other values of r. For example, with r = 99.96 it becomes a T(3,2) torus knot.

## References

• Art and Cultures
• Countries of the World (http://www.academickids.com/encyclopedia/index.php/Countries)
• Space and Astronomy