Displaying similar documents to “Picard groups of Deligne-Lusztig varieties -- with a view toward higher codimensions.”

Schubert varieties, toric varieties and ladder determinantal varieties

Nicolae Gonciulea, Venkatramani Lakshmibai (1997)

Annales de l'institut Fourier

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We construct certain normal toric varieties (associated to finite distributive lattices) which are degenerations of the Grassmannians. We also determine the singular loci for certain normal toric varieties, namely the ones which are certain ladder determinantal varieties. As a consequence, we prove a refined version of the conjecture of Laksmibai & Sandhya [Criterion for smoothness of Schubert varieties in S L ( n ) / B , Proc. Ind. Acad. Sci., 100 (1990), 45-52] on the components of the singular...

Pre-Tango structures and uniruled varieties

Yoshifumi Takeda (2007)

Colloquium Mathematicae

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The pre-Tango structure is an ample invertible sheaf of locally exact differentials on a variety of positive characteristic. It is well known that pre-Tango structures on curves often induce pathological uniruled surfaces. We show that almost all pre-Tango structures on varieties induce higher-dimensional pathological uniruled varieties, and that each of these uniruled varieties also has a pre-Tango structure. For this purpose, we first consider the p-closed rational vector field...

On some numerical properties of Fano varieties

Cinzia Casagrande (2004)

Bollettino dell'Unione Matematica Italiana

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This is the text of a talk given at the XVII Convegno dell’Unione Matematica Italiana held at Milano, September 8-13, 2003. I would like to thank Angelo Lopez and Ciro Ciliberto for the kind invitation to the conference. I survey some numerical conjectures and theorems concerning relations between the index, the pseudo-index and the Picard number of a Fano variety. The results I refer to are contained in the paper [3], wrote in collaboration with Bonavero, Debarre and Druel. ...