Plücker Coordinates and the Rosenfeld Planes

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Auteur principal: Qiu, Jian
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Publié: 2024
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author Qiu, Jian
author_facet Qiu, Jian
contents The exceptional compact hermitian symmetric space EIII is the quotient $E_6/Spin(10)\times_{\mathbb{Z}_4}U(1)$. We introduce the Plücker coordinates which give an embedding of EIII into $\mathbb{C}P^{26}$ as a projective subvariety. The subvariety is cut out by 27 Plücker relations. We show that, using Clifford algebra, one can solve this over-determined system of relations, giving local coordinate charts to the space. Our motivation is to understand EIII as the complex projective octonion plane $(\mathbb{C}\otimes\mathbb{O})P^2$, whose construction is somewhat scattered across the literature. We will see that the EIII has an atlas whose transition functions have clear octonion interpretations, apart from those covering a sub-variety $X_{\infty}$ of dimension 10. This subvariety is itself a hermitian symmetric space known as DIII, with no apparent octonion interpretation. We give detailed analysis of the geometry in the neighbourhood of $X_{\infty}$. We further decompose $X={\rm EIII}$ into $F_4$-orbits: $X=Y_0\cup Y_{\infty}$, where $Y_0\sim(\mathbb{O}P^2)_{\mathbb{C}}$ is an open $F_4$-orbit and is the complexification of $\mathbb{O}P^2$, whereas $Y_{\infty}$ has co-dimension 1, thus EIII could be more appropriately denoted as $\overline{(\mathbb{O}P^2)_{\mathbb{C}}}$. This decomposition appears in the classification of equivariant completion of homogeneous algebraic varieties by Ahiezer \cite{Ahiezer}.
format Preprint
id arxiv_https___arxiv_org_abs_2401_07735
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Plücker Coordinates and the Rosenfeld Planes
Qiu, Jian
Algebraic Geometry
High Energy Physics - Theory
Differential Geometry
Symplectic Geometry
53A20, 17C40
The exceptional compact hermitian symmetric space EIII is the quotient $E_6/Spin(10)\times_{\mathbb{Z}_4}U(1)$. We introduce the Plücker coordinates which give an embedding of EIII into $\mathbb{C}P^{26}$ as a projective subvariety. The subvariety is cut out by 27 Plücker relations. We show that, using Clifford algebra, one can solve this over-determined system of relations, giving local coordinate charts to the space. Our motivation is to understand EIII as the complex projective octonion plane $(\mathbb{C}\otimes\mathbb{O})P^2$, whose construction is somewhat scattered across the literature. We will see that the EIII has an atlas whose transition functions have clear octonion interpretations, apart from those covering a sub-variety $X_{\infty}$ of dimension 10. This subvariety is itself a hermitian symmetric space known as DIII, with no apparent octonion interpretation. We give detailed analysis of the geometry in the neighbourhood of $X_{\infty}$. We further decompose $X={\rm EIII}$ into $F_4$-orbits: $X=Y_0\cup Y_{\infty}$, where $Y_0\sim(\mathbb{O}P^2)_{\mathbb{C}}$ is an open $F_4$-orbit and is the complexification of $\mathbb{O}P^2$, whereas $Y_{\infty}$ has co-dimension 1, thus EIII could be more appropriately denoted as $\overline{(\mathbb{O}P^2)_{\mathbb{C}}}$. This decomposition appears in the classification of equivariant completion of homogeneous algebraic varieties by Ahiezer \cite{Ahiezer}.
title Plücker Coordinates and the Rosenfeld Planes
topic Algebraic Geometry
High Energy Physics - Theory
Differential Geometry
Symplectic Geometry
53A20, 17C40
url https://arxiv.org/abs/2401.07735