منابع مشابه
Combinatorics of rational singularities
A normal surface singularity is rational if and only if the dual intersection graph of a desingularization satisfies some combinatorial properties. In fact, the graphs defined in this way are trees. In this paper we give geometric features of these trees. In particular, we prove that the number of vertices of valency ≥ 3 in the dual intersection tree of the minimal desingularization of a ration...
متن کاملF-rational Rings Have Rational Singularities
It is proved that an excellent local ring of prime characteristic in which a single ideal generated by any system of parameters is tightly closed must be pseu-dorational. A key point in the proof is a characterization of F-rational local rings as those Cohen-Macaulay local rings (R; m) in which the local cohomology module H d m (R) (where d is the dimension of R) have no submodules stable under...
متن کاملSingularities of rational Bézier curves
We prove that if an nth degree rational Bézier curve has a singular point, then it belongs to the two (n− 1)th degree rational Bézier curves defined in the (n− 1)th step of the de Casteljau algorithm. Moreover, both curves are tangent at the singular point. A procedure to construct Bézier curves with singularities of any order is given. 2001 Elsevier Science B.V. All rights reserved.
متن کاملA Characterization of Rational Singularities
Themain purpose of this note is to present a characterization of rational singularities in characteristic 0. The essence of the characterization is that it is enough to require less than the usual definition. Theorem 1. Let φ : Y → X be a morphism of varieties over C, and let ρ : X → Rφ∗ Y be the associated natural morphism. Assume that Y has rational singularities and there exists a morphism (...
متن کاملRational Singularities Associated to Pairs
Rational singularities are a class of singularities which have been heavily studied since their introduction in the 1960s. Roughly speaking, an algebraic variety has rational singularities if its structure sheaf has the same cohomology as the structure sheaf of a resolution of singularities. Rational singularities enjoy many useful properties, in particular they are both normal and Cohen-Macaul...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Journal of Commutative Algebra
سال: 2018
ISSN: 1939-2346
DOI: 10.1216/jca-2018-10-3-375