Bijection between standard pairs and web basis indices

Let M{\mathcal{M}} be a positroid, and let an ordered pair (I,J)(I,J) of kk-element subsets be M{\mathcal{M}}-standard if I=πk(x)I=\pi_k(x) and J=πk(y)J=\pi_k(y) for some uxyvu\leq x\leq y\leq v, where uvu\leq v is an interval in Bruhat order such that the Richardson subvariety XuvX^v_u projects birationally to the positroid variety ΠM\Pi_{\mathcal{M}}. Let A(M){\mathcal{A}}({\mathcal{M}}) denote the indexing set of the basis constructed in the paper, and let θ\theta be the map of Proposition. The standard-pair bijection conjecture. The map θ\theta restricts to a bijection between M{\mathcal{M}}-standard pairs (I,J)(I,J) and the set A(M){\mathcal{A}}({\mathcal{M}}). This would identify the standard-monomial degree-two basis of C[ΠM]{\mathbb C}[\Pi_{\mathcal{M}}] with the basis indexed by A(M){\mathcal{A}}({\mathcal{M}}), clarifying the relationship between standard monomials and the dimer/web construction. The supplied text gives no resolution status.

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Primary source

Thomas Lam, “Dimers, webs, and positroids”, arXiv:1404.3317 (2014).

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