The strong rearrangement bijection conjecture for generalized factor order

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Let P∗\mathbb{P}^* be the set of finite words over the positive integers, let F(u)\mathcal{F}(u) denote the set of words containing uu as a factor in generalized factor order, and let u∽vu\backsim v denote Wilf equivalence. A bijection is weight-preserving when it preserves the weight of every word, and a word is a rearrangement of another when it has the same multiset of letters. Strong rearrangement bijection conjecture. If u∽vu\backsim v, then there is a weight-preserving bijection

f:P∗⟶P∗f:\mathbb{P}^*\longrightarrow\mathbb{P}^*

such that for every w∈P∗w\in\mathbb{P}^*, f(w)f(w) is a rearrangement of ww and

w∈F(u)  ⟺  f(w)∈F(v).w\in\mathcal{F}(u)\iff f(w)\in\mathcal{F}(v).

This would strengthen the weak rearrangement conjecture by realizing Wilf equivalence through a letter-rearranging bijection, and is left open in the paper.

References

Primary source

Thomas Langley, Jeffrey Liese and Jeffrey Remmel, “Generating functions for Wilf equivalence under generalized factor order”, arXiv:1005.4372 (2010).

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