xt+1 = 1.0 + μ (xt cosθt - yt sinθt)

yt+1 = μ (xt sinθt + yt cosθt)

θt = a - b/(1.0 + xt2  + yt2)

parameters: μ = 0.83, a = 0.4, b = 6.0

Lyapunov exponents (log with base-e): 0.4764, -0.8491
Lyapunov Dimension: 1.5611

The sum of the Lyapunov exponents  is theoretically the same as 2 ln(μ).

Reference

Multiple-valued stationary state and its instability of the transmitted light by a ring cavity system

Kensuke Ikeda

Optics Communications, 30, 257–261 (1979)

DOI: 10.1016/0030-4018(79)90090-7

Computing the Lyapunov spectrum of a dynamical system from an observed time series

Reggie Brown, Paul Bryant, and Henry Don Isaac Abarbanel

Physical Review A 43, 2787-2806 (1991)

DOI: 10.1103/PhysRevA.43.2787