摘要:

The present note is motivated by the following well known result about vector bundles on projective space

ISSN:0092-7872    

DOI:10.1080/00927879508825380

出版商:Marcel Dekker, Inc.    

年代:1995

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927879508825381

出版商:Marcel Dekker, Inc.    

年代:1995

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927879508825382

出版商:Marcel Dekker, Inc.    

年代:1995

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927879508825383

出版商:Marcel Dekker, Inc.    

年代:1995

数据来源: Taylor

摘要:

For every biliaison classCMof Buchsbaum curves of π3we prove that the leftmost shift in which there are smooth and connected curves is the same as for irreducible curves. As a consequence, every irreducible Buchsbaum curve has a flat deformation with cohomology and Hartshorne-Rao module constant which is smooth and connected.

ISSN:0092-7872    

DOI:10.1080/00927879508825384

出版商:Marcel Dekker, Inc.    

年代:1995

数据来源: Taylor

摘要:

We give a new proof of the structure theorem for PSH—algebras, and of a formula for primitives

ISSN:0092-7872    

DOI:10.1080/00927879508825385

出版商:Marcel Dekker, Inc.    

年代:1995

数据来源: Taylor

摘要:

Shapovalov introduced elements in the enveloping algebra of a semi-simple Lie algebra that when applied to the highest weight vector of a Verma module generated a Verma submodule. A Shapovalov element induces a containment of Verma modules uniformly across all highest weights in a particular root hyperplane. As a consequence of the Jantzen conjecture, the generator of a Verma submodule is known to lie in a definite level of the Jantzen filtration of the Verma module. Is it possible to choose a Shapovalov element that will place itself naturally into the correct filtration level uniformly across the root hyperplane? This paper considers this problem in the case ofsl(n). There are weights, called singular weights, where such Shapovalov elements cannot exist even in a local sense. What then can be said for the non-singular weights? A system of elements is introduced using Carter’s theory of lowering operators ([C]). In the examples, given any non-singular weight, there is an element of this system that provides a local solution to the problem. It is conjectured that this description extends to the general case and characterizes the singular weights.

ISSN:0092-7872    

DOI:10.1080/00927879508825386

出版商:Marcel Dekker, Inc.    

年代:1995

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927879508825387

出版商:Marcel Dekker, Inc.    

年代:1995

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927879508825388

出版商:Marcel Dekker, Inc.    

年代:1995

数据来源: Taylor

摘要:

Almost-crystallographic groups arise as a natural generalization of the well known crystallographic groups. Automorphisms and outer automorphisms of crystallographic groups were treated in [l] (see also [2]). In [10], we developed a method to describe Aut(E) and Out(E) for an almost-crystallographic groupEin terms of commutative diagrams with calculable entries. Here, we continue this study from a different point of view, namely we search for almost-crystallographic groups admitting many (outer) automorphisms. The aim of this paper is to indicate situations in which we can explicitly construct free abelian groups of (outer) automorphisms. Moreover, in many cases, these groups are normal in the full group of (outer) automorphisms. The results obtained are not only of pure algebraic interest, as it is well known that forK(E, l)-manifolds, Out(E) has a relevant geometrical meaning

ISSN:0092-7872    

DOI:10.1080/00927879508825389

出版商:Marcel Dekker, Inc.    

年代:1995

数据来源: Taylor