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arXiv 1503.00427cond-mat.stat-mech
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Logistic映射中随机性的影响

Effect of randomness in logistic maps

Abdul Khaleque, Parongama Sen

摘要:

研究了随机Logistic映射$x_{t+1} = a_{t} x_{t}[1-x_{t}]$,其中$a_t$是有界的($q_1 \leq a_t \leq q_2$),随机变量独立地从一个分布中抽取. $x_t$未及时显示任何常规行为。我们发现,$x_t$显示完全遍历行为时,$a_t$的最大允许值是$4$。然而,在不同实现上平均的$< x_{t \to \infty}>$达到固定点。对于$1\leq a_t \leq 4$的系统表现出非混沌行为和李雅普诺夫指数是强烈依赖于分布的不对称性,从中$a_t$。当$q_2$($q_1$)变化时,可以看到在超过阈值$q_1$($q_2$)时发生混沌行为。最显著的结果是,即使当$q_2$小于非随机映射发生混沌的阈值$3.5699......$时,随机映射也是混沌的。我们还采用了一种不同的方法,其中一组不同的随机变量用于两个初始相同的$x$值的演变,这里的混沌政权存在于所有$q_1 \neq q_2 $值。

英文摘要:

We study a random logistic map $x_{t+1} = a_{t} x_{t}[1-x_{t}]$ where $a_t$ are bounded ($q_1 \leq a_t \leq q_2$), random variables independently drawn from a distribution. $x_t$ does not show any regular behaviour in time. We find that $x_t$ shows fully ergodic behaviour when the maximum allowed value of $a_t$ is $4$. However $< x_{t \to \infty}>$, averaged over different realisations reaches a fixed point. For $1\leq a_t \leq 4$ the system shows nonchaotic behaviour and the Lyapunov exponent is strongly dependent on the asymmetry of the distribution from which $a_t$ is drawn. Chaotic behaviour is seen to occur beyond a threshold value of $q_1$ ($q_2$) when $q_2$ ($q_1$) is varied. The most striking result is that the random map is chaotic even when $q_2$ is less than the threshold value $3.5699......$ at which chaos occurs in the non random map. We also employ a different method in which a different set of random variables are used for the evolution of two initially identical $x$ values, here the chaotic regime exists for all $q_1 \neq q_2 $ values.

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