منابع مشابه
Schubert unions in Grassmann varieties
We study subsets of Grassmann varieties G(l, m) over a field F , such that these subsets are unions of Schubert cycles, with respect to a fixed flag. We study the linear spans of, and in case of positive characteristic, the number of Fq-rational points on such unions. Moreover we study a geometric duality of such unions, and give a combinatorial interpretation of this duality. We discuss the ma...
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For integers m ≥ p ≥ 2, let GR = GR(m,m + p) ⊂ RP N be the Plücker embedding of the Grassmannian of m-subspaces in Rm+p . We consider a central projection of GR into a projective space RP mp of the same dimension as GR . Although GR may be non-orientable, the topological degree of this projection can be properly defined. Its values are unsigned integers. It turns out that when mp is even, the d...
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We compute the total Witt groups of (split) Grassmann varieties, over any regular base X. The answer is a free module over the total Witt ring of X. We provide an explicit basis for this free module, which is indexed by a special class of Young diagrams, that we call even Young diagrams.
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Following Weyl’s account in The Classical Groups we develop an analogue of the (first and second) Fundamental Theorems of Invariant Theory for rings of differential operators: when V is a k-dimensional complex vector space with the standard SLkC action, we give a presentation of the ring of invariant differential operators D(C[V n])SLkC and a description of the ring of differential operators on...
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An embedding of a point-line geometry Γ is usually defined as an injective mapping ε from the point-set of Γ to the set of points of a projective space such that ε(l) is a projective line for every line l of Γ. However, different situations are considered in the literature, where ε(l) is allowed to be a subline of a projective line or a curve. In this paper we propose a more general definition ...
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ژورنال
عنوان ژورنال: Nagoya Mathematical Journal
سال: 1977
ISSN: 0027-7630,2152-6842
DOI: 10.1017/s0027763000017761