The necessity conjecture for intermediate crossing–uncrossing pairs in Go-diagrams

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Let D′D' be a Go-diagram in a partition λ\lambda, and let c≺c′c\prec c' be a crossing and uncrossing pair in D′D' with D′(c)=∘D'(c)=\circ. Let DD be obtained by replacing the stones at cc and c′c' with ++. Let i<ji<j be the labels of the pipes crossing at cc in D′D'. The necessity conjecture. Suppose that, after recolouring stones appropriately, DD is a Go-diagram with no cells in the forbidden configuration, and that there is a label kk with i<k<ji<k<j such that kk forms a crossing and uncrossing pair with ii or jj between cc and c′c' in D′D'. Then

DD′⊄DD‾.\mathcal{D}_{D'}\not\subset\overline{\mathcal{D}_D}.

The source presents this as the conjectured necessity of the second condition in the preceding closure conjecture. It is motivated by the failure of the first condition alone, but no proof or resolution is supplied.

References

Primary source

Kartik Singh, “Parametrizing the Grassmannian using pipe dreams”, arXiv:2511.07627 (2025).

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