Given a germ of holomorphic function on , we study the condition: “the ideal is generated by operators of order1”. We obtain here full characterizations in the particular cases of Koszul-free germs and unreduced germs of plane curves. Moreover, we prove that this condition holds for a special type of hyperplane arrangements. These results allow us to link this condition to the comparison of de Rham complexes associated with .
The goal of this work is to construct, for a smooth variety over a perfect field k of finite characteristic , an overconvergent de Rham-Witt complex as a suitable subcomplex of the de Rham-Witt complex of Deligne-Illusie. This complex, which is functorial in , is a complex of étale sheaves and a differential graded algebra over the ring of overconvergent Witt-vectors. If is affine one proves that there is an isomorphism between Monsky-Washnitzer cohomology and (rational) overconvergent...
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...
We derive a simple formula for the action of a finite crystallographic Coxeter group on the cohomology of its associated complex toric variety, using the method of counting rational points over finite fields, and the Hodge structure of the cohomology. Various applications are given, including the determination of the graded multiplicity of the reflection representation.
Dans l’exposé Bourbaki 409, Katz conjecture la méromorphie -adique de la fonction attachée à une variété lisse sur un corps fini () et à un -cristal sur . Si est propre et lisse sur nous prouvons que est rationnelle et fournie par l’expression habituelle utilisant l’action du Frobenius sur la cohomologie cristalline à coefficients dans ; ce résultat n’était connu, via les “conjectures de Weil”, que pour des -cristaux unités particuliers: ceux provenant d’une représentation de...