Abstract
In this paper we show a construction, inductive onn, of the Grassmannian\(\mathcal{G}_{n,1,F}\) representing the lines of the projective spaceP n,F :\(\mathcal{G}_{n,1,F}\) is the union of those planes, any of which is obtained by joining a line of a certain (n−1)-flat S n−1 with the corresponding point on\(\mathcal{G}_{n - 1,1,F}\) via the Plücker mapping; it is assumed that the\(\left( {\left( {\begin{array}{*{20}c} n \\ 2 \\ \end{array} } \right) - 1} \right)\)-flat spanned by this\(\mathcal{G}_{n - 1,1,F}\) is skew with S n−1.
Every embedded Grassmann space can be obtained from a Grassmannian by projecting it on a subspaceS from another one, sayS′ (the vertex of the projection). This is a consequence of the description of all projective embeddings of the Grassmann spaces given by HAVLICEK [4] and WELLS [9]. When the vertexS′ is not empty, we say that the embedded Grassmann space is a projected Grassmannian. Since examples of projected Grassmannians do exist, the embedded\(\mathcal{G}_{n,h,F}\)'s cannot, in general, be projectively characterized by using only their intrinsic incidence properties. We show that for any fieldF, the projection is impossible exactly forn=3,4. In every other case the dimension of the vertex can depend onF.
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This paper has been prepared from some results of a research project supported by N.A.T.O.
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Zanella, C. Embeddings of Grassmann spaces. J Geom 52, 193–201 (1995). https://doi.org/10.1007/BF01406840
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DOI: https://doi.org/10.1007/BF01406840