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arXiv 0909.1445cond-mat.stat-mechq-bio.PE
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逃避猎物的生存

Survival of an evasive prey

G. Oshanin, O. Vasilyev, P. L. Krapivsky, J. Klafter

摘要:

我们研究被N个捕食者捕食的猎物的生存。捕食者执行独立的随机行走在一个正方形格子与V网站,并开始直接追逐时,猎物出现在他们的视线范围内。当捕食者跳到猎物所占据的位置时,猎物就被抓住了。我们分析了一个懒惰的,最小的努力逃避策略的有效性,根据该策略,猎物试图避免遇到捕食者,使一跳,只有当任何捕食者出现在其视线范围内,否则猎物保持静止。我们表明,如果这样一个懒惰的猎物的视线范围是等于1格间距,至少需要3个捕食者,以赶上猎物的正方形格子。在这种情况下,我们建立了一个简单的渐近关系ln(Pev)(t)\sim(N/V)2ln(Pimm(t))之间的生存概率逃避和不动的猎物。因此,当捕食者密度较低(N/V<<1)时,懒惰逃避策略导致生存概率的显著增加。我们还认为,一个短视的猎物(它的视线范围小于捕食者的视线范围)经历了有效的superdiffusive运动,由于它遇到的捕食者,而一个远视的猎物进行扩散型运动。

英文摘要:

We study the survival of a prey that is hunted by N predators. The predators perform independent random walks on a square lattice with V sites and start a direct chase whenever the prey appears within their sighting range. The prey is caught when a predator jumps to the site occupied by the prey. We analyze the efficacy of a lazy, minimal-effort evasion strategy according to which the prey tries to avoid encounters with the predators by making a hop only when any of the predators appears within its sighting range; otherwise the prey stays still. We show that if the sighting range of such a lazy prey is equal to 1 lattice spacing, at least 3 predators are needed in order to catch the prey on a square lattice. In this situation, we establish a simple asymptotic relation ln(Pev)(t) \sim (N/V)2ln(Pimm(t)) between the survival probabilities of an evasive and an immobile prey. Hence, when the density of the predators is low N/V<<1, the lazy evasion strategy leads to the spectacular increase of the survival probability. We also argue that a short-sighting prey (its sighting range is smaller than the sighting range of the predators) undergoes an effective superdiffusive motion, as a result of its encounters with the predators, whereas a far-sighting prey performs a diffusive-type motion.

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