1a) In this exercise we look at the shifted logistic map with zero mean.
\[ x_{t+1}=4(0.5+x_{t})(0.5-x_{t})-0.5 \]def logistic_map( x ):
in Pythonplt.plot()
numpy.random.uniform( -0.5,0.5,200 )
) with length 5001b) The output of a chaotic map generates pseudo-random numbers. The cummulative sum of such pseudo-random numbers with zero mean is pseudo-Brownian motion.
numpy.cumsum( x )
def ta_msd( ts ):
l = len(ts)-1
TAMSD = np.zeros(l)
for Delta in range(1,l+1):
TAMSD[Delta-1] = ( np.mean( ( ts[Delta:]-ts[:-Delta] )**2 ,axis=0) )
return TAMSD
2a) An other map, called the Pomeau-Manneville map is given by the iteration relation
\[ x_{t+1}=\left\lbrace\begin{array}{ll} {-4x_t-3} & \mbox{ for } -0.5>x_t>-1 \\ x_{t}(1+|2x_{t}|^{z-1}) & \mbox{ for } 0.5>|x_t| \\ -4x_t+3 & \mbox{ for } 1>x_t>0.5\end{array}\right. \]2b) The MSD for this type of pseudo-Brownian motion scales with an exponent different from 1