Abstract
We study families of linear spaces in projective space whose union is a proper subvariety $X$ of the expected dimension. We establish relations between configurations of focal points and the existence or non-existence of a fixed tangent space to $X$ along a general element of the family. We apply our results to the classification of ruled $3$-dimensional varieties.
Citation
E. Mezzetti. O. Tommasi. "On projective varieties of dimension $n+k$ covered by $k$-spaces." Illinois J. Math. 46 (2) 443 - 465, Summer 2002. https://doi.org/10.1215/ijm/1258136202
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