Saturated-valuation construction of unipotent bicrystals

Let YY^\vee be an affine GG^\vee-variety, let SS be a split algebraic torus, and let \prec be a total ordering on the cocharacter lattice X(S)X_\star(S). Assume there are a saturated valuation

ν:C[Y]{0}(X(S),)\nu:\mathbb{C}[Y^\vee]\setminus\{0\}\to (X_\star(S),\prec)

and a perfect basis B{\bf B} for C[Y]\mathbb{C}[Y^\vee] such that the restriction of ν\nu to B{\bf B} is injective. Then there exists a strongly positive (U,χst)(U,\chi^{st})-linear bicrystal (X,p,f,Θ)({\bf X},{\bf p},f,\Theta), with an isomorphism θ:SX\theta:S\overset\sim\to X^-, for which the image of the valuation-induced crystal map is Bf,ΘX(S)\mathcal{B}_{f,\Theta}\subset X_\star(S) and induces an isomorphism

B(C[Y])Bf,Θ.\mathcal{B}(\mathbb{C}[Y^\vee])\overset\sim\to \mathcal{B}_{f,\Theta}.

Saturated-valuation conjecture. Under these assumptions, such a strongly positive unipotent bicrystal exists and the valuation-induced map identifies the normal crystal of C[Y]\mathbb{C}[Y^\vee] with Bf,Θ\mathcal{B}_{f,\Theta}.

The conjecture gives sufficient conditions for constructing strongly positive unipotent bicrystals from affine GG^\vee-varieties, saturated valuations, and perfect bases. The source presents it as a route toward constructing bicrystals for suitable varieties; no resolution is stated.

Sources & referencesView supporting material

Primary source

Arkady Berenstein and David Kazhdan, “Geometric and unipotent crystals II: From unipotent bicrystals to crystal bases”, arXiv:math/0601391 (2007).

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