摘要:

Letkbe an algebraically closed field, chark= 0. LetCbe an irreducible nonsingular curve such that 2C=S⋂F, whereSandFare two surfaces and all the singularities ofFare rational double points (if any). We prove thatCcan never pass through rational singularities of typesA2nn∈N, E6and E8. We give conditions forCto pass through rational singularities of types.A2k+1k∈Z+Dnn≥4 and E7, (0.8).

ISSN:0092-7872    

DOI:10.1080/00927870008827191

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

摘要:

The authors are glad for the opportunity to contribute to a volume in honour of professor Hartshorne, whose works always stands as a basic reference for researchers in Algebraic Geometry.

ISSN:0092-7872    

DOI:10.1080/00927870008827192

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

摘要:

In this note we partially extend results on the finite-ness properties of local cohomology modules from the case of a regular local ring containing a field to the unramified case of a regular local ring of mixed characteristic.

ISSN:0092-7872    

DOI:10.1080/00927870008827193

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

摘要:

We determine the triplesF,G,Hof vector bundles of finite rank on P1which may fit in an exact sequence 0→F→G→H→0.

ISSN:0092-7872    

DOI:10.1080/00927870008827194

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

摘要:

We construct families of normal surface singularities with the following property: given any fiat projective connected familyV→Bof smooth, irreducible, minimal algebraic surfaces, the general singularity in one of our families cannot occur, analytically, on any algebraic surfaces which is Irrationally equivalent to a surface inV→B. In particular this holds forV→Bconsisting of a single rational surface, thus answering negatively to a long standing problem posed by F. Enriques. In order to prove the above mentioned results, wo develop a general, though elementary, method, based on the consideration of suitable correspondences, for comparing a given family of minimal surfaces with a family of surface singularities. Specifically the method in question gives us the possibility of comparing the parameters on which the two families depend, thus leading to the aforementioned results.

ISSN:0092-7872    

DOI:10.1080/00927870008827195

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927870008827196

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927870008827197

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927870008827198

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

摘要:

We sharpen the two main tools used to treat the compactified Jacobian of a singular curve: Abel maps and presentation schemes. First we prove a smoothness theorem for bigraded Abel maps. Second we study the two complementary filtrations provided by the images of certain Abel maps and certain presentation schemes. Third we study a lifting of the Abel map of bidegree (m, 1) to the corresponding presentation scheme. Fourth we prove that, if a curve is blown up at a double point, then the corresponding presentation scheme is a1-bundle. Finally, using Abel maps of bidegree (m, 1), we characterize the curves having double points at worst.

ISSN:0092-7872    

DOI:10.1080/00927870008827199

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927870008827200

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor