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Note: Here time is assumed to be discrete and indexed by the naturals $\mathbb N$.

A curious species of amoeba undergoes the following evolution rule - at each time step, with probability $0 < p < 1$ it splits into two copies of itself of size $\varepsilon S$, where $S$ is the original size of the amoeba, and $0 < \varepsilon < 1$ is a fixed number. With probability $q = 1-p$, it doubles in size instead.

Start with one amoeba of size $1$. Denoting by $S^{\max}_t$ the size of the largest amoeba at time $t$, for what values of the parameters $\varepsilon, p$ do we have

$$\lim_{t \to \infty} S^{\max}_t = \infty$$

almost surely?

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    $\begingroup$ I thought for a second there that the post was about tropical geometry :-) $\endgroup$
    – M.G.
    Commented 14 hours ago
  • $\begingroup$ @M.G. Unfortunately it is about fictional amoeba, not mathematical amoeba :P $\endgroup$
    – Nate River
    Commented 14 hours ago
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    $\begingroup$ Great question. +1 $\endgroup$
    – user531372
    Commented 13 hours ago
  • $\begingroup$ Does $S$ denote the starting size of the amoeba (which you said is $1$) or the size right before splitting? $\endgroup$ Commented 2 hours ago
  • $\begingroup$ Also, you said "it" after talking about the species, which I think you didn't mean to do. Is each amoeba evolving according to the rule (simultaneously)? $\endgroup$ Commented 2 hours ago

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