摘要:

We show that Severi varieties of sufficiently nodal plane curves have rational Picard group zero. The technique is to factor the natural map from the Severi variety to the moduli space of curves into a composition of fibrations each of which is well understood.

ISSN:0092-7872    

DOI:10.1080/00927879408824956

出版商:Gordon and Breach Science Publishers Ltd.    

年代:1994

数据来源: Taylor

摘要:

The Principal Ideal Theorem states that ifReis a commutative Noetherian ring and ? is a prime ideal ofRewhich is minimal over a principal ideal thenPehas height at most 1. Also, ifReis a (not necessarily Noetherian) UFD andPeis a prime ideal ofReminimal over a principal ideal thenPehas height at most 1. We shall show that there are analogues for modules over commutative rings, but they hold only in special cases.

ISSN:0092-7872    

DOI:10.1080/00927879408824957

出版商:Gordon and Breach Science Publishers Ltd.    

年代:1994

数据来源: Taylor

摘要:

It is known that many special radicalsRsatisfy the matrix conditionan arbitrary ring, but that these radicals do not carry over from the base ringRto structural matrix rings in this natural way. In this paper we study the radicals (of structural matrix rings) determined by some polynomial regularities. We obtain various classes of polynomial regularities and classes of structural matrix rings for which the corresponding radicals behave differently from special radicals. For example, on the one hand, some radicals carry over to certain structural matrix rings in the mentioned natural way, whereas on the other hand it might happen that the radical of a structural matrix ring, which is not a complete matrix ring, is {0}, in spite of the fact that sucha radical satisfies the matrix condition, for example the Von Neumann radical. It turns out that the presence or absence of reflexivity and antisymmetry of the underlying Boolean matrix of a structural matrix ring plays a crucial role in this regard.

ISSN:0092-7872    

DOI:10.1080/00927879408824958

出版商:Gordon and Breach Science Publishers Ltd.    

年代:1994

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927879408824959

出版商:Gordon and Breach Science Publishers Ltd.    

年代:1994

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927879408824960

出版商:Gordon and Breach Science Publishers Ltd.    

年代:1994

数据来源: Taylor

摘要:

We prove here the validity of the cohomological Hasse principle for almost simple simply connected groups of classical type defined over the rational real function field R(t) and the Hasse principle (analog of the Platonov conjecture) about the projective simplicity of the groups of rational points of such groups.

ISSN:0092-7872    

DOI:10.1080/00927879408824961

出版商:Gordon and Breach Science Publishers Ltd.    

年代:1994

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927879408824962

出版商:Gordon and Breach Science Publishers Ltd.    

年代:1994

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927879408824963

出版商:Gordon and Breach Science Publishers Ltd.    

年代:1994

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927879408824964

出版商:Gordon and Breach Science Publishers Ltd.    

年代:1994

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927879408824965

出版商:Gordon and Breach Science Publishers Ltd.    

年代:1994

数据来源: Taylor