combinatorics / Permutation combinatorics

The Proportion of Permutations Fixing a k-Set

An asymptotic formula for $p(k)$, the limiting probability that a random permutation has an invariant set of size $k$: it is asymptotically $k^{-\delta}(1+o(1))$ times a smooth positive function, sharpening a line of estimates running through Łuczak-Pyber and Eberhard-Ford-Green.

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combinatoricsApr 30, 2026Significance 15/100Registry: unreviewed

The Proportion of Permutations Fixing a k-Set

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An asymptotic formula for $p(k)$, the limiting probability that a random permutation has an invariant set of size $k$: it is asymptotically $k^{-\delta}(1+o(1))$ times a smooth positive function, sharpening a line of estimates running through Łuczak-Pyber and Eberhard-Ford-Green.

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An asymptotic formula for $p(k)$, the limiting probability that a random permutation has an invariant set of size $k$: it is asymptotically $k^{-\delta}(1+o(1))$ times a smooth positive function, sharpening a line of estimates running through Łuczak-Pyber and Eberhard-Ford-Green.

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