We generalize Nakamaye’s description, via intersection theory, of the augmented base locus of a big and nef divisor on a normal pair with log-canonical singularities or, more generally, on a normal variety with non-lc locus of dimension . We also generalize Ein-Lazarsfeld-Mustaţă-Nakamaye-Popa’s description, in terms of valuations, of the subvarieties of the restricted base locus of a big divisor on a normal pair with klt singularities.
In this note we study deformations of a plane curve singularity (C,P) toδ(C,P) nodes. We see that for some types of singularities the method of A'Campo can be carried on using parametric equations. For such singularities we prove that deformations to δ nodes can be made within the space of curves of the same degree.
Nous donnons un résumé des principaux résultats récents obtenus sur les nœuds algébriques.
The hypersurface in with an isolated quasi-homogeneous elliptic singularity of type , has a natural Poisson structure. We show that the family of del Pezzo surfaces of the corresponding type provides a semiuniversal Poisson deformation of that Poisson structure. We also construct a deformation-quantization of the coordinate ring of such a del Pezzo surface. To this end, we first deform the polynomial algebra to a noncommutative algebra with generators and the following 3 relations labelled...
Using BMY inequality and a Milnor number bound we prove that any algebraic annulus in with no self-intersections can have at most three cuspidal singularities.