Conjecture on the longest increasing subsequence of conjugation-invariant permutations

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Let (τn)n(\tau_n)_n be a sequence of conjugation-invariant random permutations, where τn\tau_n has size nn and random cycle type t(n)t^{(n)}. Suppose that

t1(n)/n⟶0t_1^{(n)}/\sqrt{n}\longrightarrow0

in probability. Conjecture on the longest increasing subsequence. Then

1nLIS⁡(τn)⟶n→∞2\frac{1}{\sqrt{n}}\operatorname{LIS}(\tau_n)\underset{n\to\infty}{\longrightarrow}2

in probability. The result would identify the same first-order asymptotic as for uniform permutations when the number of fixed points is negligible compared with n\sqrt n; related cases are known for random involutions and under additional cycle constraints.

References

Primary source

Victor Dubach, “A geometric approach to conjugation-invariant random permutations”, arXiv:2402.10116 (2025).

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