The generating rank of the unitary and symplectic Grassmannians

We prove that the Grassmannian of totally isotropic $k$-spaces of the polar space associated to the unitary group $\mathsf{SU}_{2n}(\mathbb{F})$ ($n\in \mathbb{N}$) has generating rank ${2n\choose k}$ when $\mathbb{F}\ne \mathbb{F}_4$. We also reprove the main result of Blok [Blok2007], namely that the Grassmannian of totally isotropic $k$-spaces associated to the symplectic group $\mathsf{Sp}_{2n}(\mathbb{F})$ has generating rank ${2n\choose k}-{2n\choose k-2}$, when $\rm{Char}(\mathbb{F})\ne 2$

Hyperplanes of symplectic dual polar spaces : a survey

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Hyperplanes of Hermitian dual polar spaces of rank 3 containing a quad

Let F and F' be two fields such that F' is a quadratic Galois extension of F. If vertical bar F vertical bar >= 3, then we provide sufficient conditions for a hyperplane of the Hermitian dual polar space DH(5, F') to arise from the Grassmann embedding. We use this to give an alternative proof for the fact that all hyperplanes of DH(5, q(2)), q not equal 2, arise from the Grassmann embedding, and to show that every hyperplane of DH(5, F') that contains a quad Q is either classical or the extension of a non-classical ovoid of Q. We will also give a classification of the hyperplanes of DH(5, F') that contain a quad and arise from the Grassmann embedding

On extensions of hyperplanes of dual polar spaces

AbstractLet Δ be a thick dual polar space and F a convex subspace of diameter at least 2 of Δ. Every hyperplane G of the subgeometry F˜ of Δ induced on F will give rise to a hyperplane H of Δ, the so-called extension of G. We show that F and G are in some sense uniquely determined by H. We also consider the following problem: if e is a full projective embedding of Δ and if eF is the full embedding of F˜ induced by e, does the fact that G arises from the embedding eF imply that H arises from the embedding e? We will study this problem in the cases that e is an absolutely universal embedding, a minimal full polarized embedding or a Grassmann embedding of a symplectic dual polar space. Our study will allow us to prove that if e is absolutely universal, then also eF is absolutely universal

Hyperplanes of DW(5,K) with K a perfect field of characteristic 2

Let K be a perfect field of characteristic 2. In this paper, we classify all hyperplanes of the symplectic dual polar space DW(5, K) that arise from its Grassmann embedding. We show that the number of isomorphism classes of such hyperplanes is equal to 5 + N, where N is the number of equivalence classes of the following equivalence relation R on the set {lambda is an element of K|X(2) + lambda X + 1 is irreducible in K[X]}: (lambda(1), lambda(2)) is an element of R whenever there exists an automorphism sigma of K and an a is an element of K such that (lambda(sigma)(2))(-1) = lambda(-1)(1) + a(2) + a

An outline of polar spaces: basics and advances

This paper is an extended version of a series of lectures on polar spaces given during the workshop and conference 'Groups and Geometries', held at the Indian Statistical Institute in Bangalore in December 2012. The aim of this paper is to give an overview of the theory of polar spaces focusing on some research topics related to polar spaces. We survey the fundamental results about polar spaces starting from classical polar spaces. Then we introduce and report on the state of the art on the following research topics: polar spaces of infinite rank, embedding polar spaces in groups and projective embeddings of dual polar spaces

Universal and homogeneous embeddings of dual polar spaces of rank 3 defined over quadratic alternative division algebras

Suppose O is an alternative division algebra that is quadratic over some subfield K of its center Z(O). Then with (O, K), there is associated a dual polar space. We provide an explicit representation of this dual polar space into a (6n + 7)-dimensional projective space over K, where n D dim(K)(O). We prove that this embedding is the universal one, provided vertical bar K vertical bar > 2. When O is not an inseparable field extension of K, we show that this universal embedding is the unique polarized one. When O is an inseparable field extension of K, then we determine the minimal full polarized embedding, and show that all homogeneous embeddings are either universal or minimal. We also provide explicit generators of the corresponding projective representations of the little projective group associated with the ( dual) polar space