The Weyl embedding conjecture for polar Grassmannians

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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(2n−1,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=ν⋅enspin.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=ν⋅enspin.\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.

References

Primary source

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

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