The Weyl embedding conjecture for polar Grassmannians

Let F\mathbb{F} be a field, let F^\widehat{\mathbb{F}} be the chosen minimal-degree separable quadratic extension in the case d0=2d_0=2, and write

Q^n=Qn(n+1,0,0;F^),Q~n=Qn(n,1,0;F^).\widehat{\mathcal{Q}}_n=\mathcal{Q}_n(n+1,0,0;\widehat{\mathbb{F}}),\qquad \widetilde{\mathcal{Q}}_n=\mathcal{Q}_n(n,1,0;\widehat{\mathbb{F}}).

Let e^nW\widehat{e}^W_n be the Weyl embedding of Q^n\widehat{\mathcal{Q}}_n, let e~nW\widetilde{e}^W_n be the canonical veronesean embedding of Q~n\widetilde{\mathcal{Q}}_n, and let enWe^W_n be the Weyl-like embedding of Qn\mathcal{Q}_n with codomain VkWV^W_k. Let enspine^{\mathrm{spin}}_n denote the spin-like embedding of Qn\mathcal{Q}_n, and let ν\nu be the canonical veronesean embedding of PG(2n1,F)\mathrm{PG}(2^n-1,\mathbb{F}) in PG((2n+12)1,F)\mathrm{PG}({{2^n+1}\choose 2}-1,\mathbb{F}).

The Weyl embedding conjecture. The Weyl embedding e^nW\widehat{e}^W_n of Q^n\widehat{\mathcal{Q}}_n induces on Q~n\widetilde{\mathcal{Q}}_n its veronesean embedding e~nW\widetilde{e}^W_n, the codomain VkWV^W_k of enWe^W_n is the canonical Baer subgeometry of PG((2n+12)1,F^)\mathrm{PG}({{2^n+1}\choose 2}-1,\widehat{\mathbb{F}}) defined over F\mathbb{F}, and e~nW\widetilde{e}^W_n induces enWe^W_n on Qn\mathcal{Q}_n. Consequently,

enW=νenspin.e^W_n=\nu\cdot e^{\mathrm{spin}}_n.

In particular, if enW=εne^W_n=\varepsilon_n, as when char(F)2\operatorname{char}(\mathbb{F})\neq 2, then

εn=νenspin.\varepsilon_n=\nu\cdot e^{\mathrm{spin}}_n.

The conjecture concerns the compatibility of the Weyl, spin-like, and veronesean embeddings under the inclusions of these polar Grassmannians; the statement is presented as an unproved expectation, and no resolution is supplied in the source.

Sources & referencesView supporting material

Primary source

Ilaria Cardinali, Luca Giuzzi and Antonio Pasini, “Grassmann embeddings of polar Grassmannians”, arXiv:1810.12811 (2019).

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