The \operatorname{SC}_{132} image conjecture for maximally nonperiodic permutations

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Let s132s_{132} be the classical stack-sorting map associated with the pattern 132132, let Av⁡(132,231)\operatorname{Av}(132,231) denote the permutations avoiding 132132 and 231231, and define Vn{\bf V}_n by listing the odd elements of [n][n] in decreasing order followed by the even elements in increasing order when nn is odd, with the analogous even-then-odd construction when nn is even.

\operatorname{SC}_{132} image conjecture. If τ∈Sn\tau\in S_n satisfies

s132n−2(τ)∉Av⁡(132,231),s_{132}^{n-2}(\tau)\notin\operatorname{Av}(132,231),

then

s132n−1(τ)=Vn.s_{132}^{n-1}(\tau)={\bf V}_n.

The claim concerns permutations whose second-to-last iterate has not yet entered the known periodic-point set; the paper presents it as an additional open dynamical question.

References

Primary source

Colin Defant and Kai Zheng, “Stack-Sorting with Consecutive-Pattern-Avoiding Stacks”, arXiv:2008.12297 (2020).

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