Recursive criterion for record-equivalence of permutation patterns

From papers

Fix k2k\ge2 and let π,σSk\pi,\sigma\in S_k. For a permutation ww, let Rec(w)\mathrm{Rec}(w) denote its record set. Define record-equivalence by equality of the numbers of avoiders with each record set at every length. For i[k]i\in[k], let π(i)\pi^{(i)} and σ(i)\sigma^{(i)} be the standardized permutations obtained by deleting position ii, and let mπ=π1(k)m_\pi=\pi^{-1}(k) and mσ=σ1(k)m_\sigma=\sigma^{-1}(k).

Recursive criterion for record-equivalence. The permutations π\pi and σ\sigma are record-equivalent if and only if all of the following hold:

  1. Rec(π)=Rec(σ)\mathrm{Rec}(\pi)=\mathrm{Rec}(\sigma).
  2. Avn(π)=Avn(σ)|\operatorname{Av}_n(\pi)|=|\operatorname{Av}_n(\sigma)| for all nkn\ge k.
  3. If mπ=mσm_\pi=m_\sigma, then for every i[k]i\in[k] with imπi\ne m_\pi, the permutations π(i)\pi^{(i)} and σ(i)\sigma^{(i)} are record-equivalent in Sk1S_{k-1}.
  4. If k4k\ge4, Rec(π)=Rec(σ)=[k1]\mathrm{Rec}(\pi)=\mathrm{Rec}(\sigma)=[k-1], and mπ=mσ=k1m_\pi=m_\sigma=k-1, then π(k)=σ(k)\pi(k)=\sigma(k).

The criterion reduces record-equivalence to record-set agreement, Wilf-equivalence, and recursive deletion-minor conditions, with a special terminal condition. The source supplies no resolution status; it is presented as a conjecture.

Progress summary

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Sources & referencesView supporting material

Primary source

Andrew Hardt, Reuven Hodges and Hanzhang Yin, “The record statistic and forward stability of Schubert products”, arXiv:2604.02964 (2026).

Solutions 0

No solutions have been posted yet.