منابع مشابه
Base subsets of symplectic Grassmannians
Let V and V ′ be 2n-dimensional vector spaces over fields F and F ′. Let also : V × V → F and ′: V ′ × V ′ → F ′ be non-degenerate symplectic forms. Denote by and ′ the associated (2n − 1)-dimensional projective spaces. The sets of kdimensional totally isotropic subspaces of and ′ will be denoted by Gk and G ′ k , respectively. Apartments of the associated buildings intersect Gk and G ′ k by so...
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Let ∆ be a thick building of type Xn = Cn,Dn. Let also Gk be the Grassmannian of k-dimensional singular subspaces of the associated polar space Π (of rank n). We write Gk for the corresponding shadow space of type Xn,k. Every bijective transformation of Gk preserving the class of base subsets (the shadows of apartments) is a collineation of Gk, and it is induced by a collineation of Π if n 6= 4...
متن کاملSymplectic subspaces of symplectic Grassmannians
Let V be a non-degenerate symplectic space of dimension 2n over the field F and for a natural number l < n denote by Cl(V ) the incidence geometry whose points are the totally isotropic l-dimensional subspaces of V . Two points U, W of Cl (V ) will be collinear when W ⊂ U⊥ and dim(U ∩ W ) = l − 1 and then the line on U and W will consist of all the l-dimensional subspaces of U + W which contain...
متن کاملFinite Subsets of Grassmannians
Let A be a subvariety of affine space A whose irreducible components are d-dimensional linear or affine subspaces of A. Denote by D(A) ⊂ N the set of exponents of standard monomials ofA. Using the Hilbert function, we show thatD(A) contains as many subspaces of dimension d as A contains irreducible components. We refine this result in various ways. Firstly, we specify the directions into which ...
متن کاملOrthogonal and Symplectic Grassmannians of Division Algebras
We consider a central division algebra (over a field) endowed with a quadratic pair or with a symplectic involution and prove 2-incompressibility of certain varieties of isotropic right ideals of the algebra. This covers a recent conjecture raised by M. Zhykhovich. The remaining related projective homogeneous varieties are 2-compressible in general. Let F be a field, n ≥ 1, D a central division...
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ژورنال
عنوان ژورنال: Journal of Algebraic Combinatorics
سال: 2007
ISSN: 0925-9899,1572-9192
DOI: 10.1007/s10801-006-0051-2