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Pre-Tango structures and uniruled varieties

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Takeda Y.

Colloquium Mathematicum

2007

tom 108

nr 2

193-216

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 induced by a pre-Tango structure, and the smoothness of the fibration induced by the p-closed rational vector field. Moreover, we give two examples: of a 3-dimensional variety of general type whose automorphism group scheme is not reduced, and of a non-uniruled variety which has a pre-Tango structure inducing a higher-dimensional pathological uniruled variety.

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1 Colloquium Mathematicum

1 Takeda Y.

1 2007

Wyniki wyszukiwania

Pre-Tango structures and uniruled varieties