Burstein–Jones dominance conjecture for vincular-pattern statistics

Let D2n1(τ)\mathfrak{D}^1_{2n}(\tau) be the Dumont-1 permutations of length 2n2n avoiding τ\tau. For a permutation π\pi, let (2-31)π(2\text{-}31)\pi and (13-2)π(13\text{-}2)\pi be the numbers of occurrences of the indicated vincular patterns, where the dash indicates that the corresponding adjacent pattern letters need not be adjacent in π\pi. Define

an,k={πD2n1(2143)(2-31)π=k},a_{n,k}=|\{\pi\in\mathfrak{D}^1_{2n}(2143)\mid (2\text{-}31)\pi=k\}|, bn,k={πD2n1(3421)(13-2)π=k}.b_{n,k}=|\{\pi\in\mathfrak{D}^1_{2n}(3421)\mid (13\text{-}2)\pi=k\}|.

Burstein–Jones's dominance conjecture. For all n0n\geq0,

an,k=bn,k=1for k=(n2),an,k=bn,k=0for k>(n2),a_{n,k}=b_{n,k}=1\quad\text{for }k=\binom{n}{2},\qquad a_{n,k}=b_{n,k}=0\quad\text{for }k>\binom{n}{2},

and

k=0man,kk=0mbn,kfor 0m(n2),\sum_{k=0}^{m}a_{n,k}\geq\sum_{k=0}^{m}b_{n,k}\quad\text{for }0\leq m\leq\binom{n}{2},

with equality when m=(n2)m=\binom{n}{2}. This refines the Wilf-equivalence conjecture by comparing distributions of vincular-pattern statistics; the source presents it as open and reports no proof beyond partial inroads.

Sources & referencesView supporting material

Primary source

Alexander Burstein and Opel Jones, “Enumeration of Dumont permutations avoiding certain four-letter patterns”, arXiv:2002.12189 (2021).

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