摘要:

We determine the signatures of the congruence subgroups of the Hecke groupsG4andG6.

ISSN:0092-7872    

DOI:10.1080/00927870008827050

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927870008827051

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

摘要:

In the setting of the complex spectrum of a field of characteristic zero we give complex analogs of the celebrated (real) Baer-Krull theorems relat-ing the orderings of a field compatible with a given valuation ring with the orderings of the residue class field of that valuation ring.

ISSN:0092-7872    

DOI:10.1080/00927870008827052

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

摘要:

This note points out a factor of the Poincaré polynomial of the λ-isotypic component of the exterior algebra λL, whereLis a complex semisimple Lie algebra and λ is a dominant weight. Although these polynomials have been studied with regard to their factorizations, this particular factor seems to have gone unstated.

ISSN:0092-7872    

DOI:10.1080/00927870008827053

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

摘要:

We investigate the Jordan structure of a prime associative superalgebra and the Jordan structure of the symmetric elements of a *-prime associative superalgebra with superinvolution.

ISSN:0092-7872    

DOI:10.1080/00927870008827054

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

摘要:

The real spectra of certain "twisted" polynomial algebrasAover R are examined. In certain cases, including Weyl algebras and universal enveloping algebras of solvable Lie algebras, the stability indices of the residue spaces of Sper(A) are estimated. The results show that the Bröcker-Scheiderer theory of minimal generation of constructible sets applies to Sper(A) in these cases. An attempt is made to compute all orderings on the Weyl algebra over R. Several open problems are mentioned.

ISSN:0092-7872    

DOI:10.1080/00927870008827055

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

摘要:

LetAbe a commutative integral domain that is a finitely generated algebra over a fieldkof characteristic 0 and let ø be ak-algebra automorphism ofAof finite orderm. In this note we study the ringD(A;ø of differential operators introduced by A.D. Bell. We prove that ifAis a free module over the fixed sub-ringAø, with a basis containing 1, thenD(A;ø) is isomorphic to the matrix ringMm(D(Aø). It follows from Grothendieck's Generic Flatness Theorem that for an arbitraryAthere is an elementcϵAsuch thatD(A[c-1];ø)≅Mm(D(A[c-1]ø)). As an application, we consider the structure ofD(A;ø)whenAis a polynomial or Laurent polynomial ring overkand ø is a diagonalizable linear automorphism.

ISSN:0092-7872    

DOI:10.1080/00927870008827056

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

摘要:

We use model-theoretic methods to give examples of pseudovaluation domains with Vapnik-Chervonenkis classes of definable sets.

ISSN:0092-7872    

DOI:10.1080/00927870008827057

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

摘要:

ATingRwith a derivation δ is called δ-semiprime if for any δ-idealIofR(i.e., an idealIsuch that δ(I)⊆I)I2= 0 impliesI= 0.Ris called δ-quasi-Baer (resp. quasi-Baer) if the right annihilator of every δ-ideal (resp. ideal) ofRis generated by an idempotent ofR. In this paper, a differential polynomial ringA = R[x;δ] of a ringRwith a derivation δ is investigated as follows: For a δ-semiprime ringR, (1)Ris δ-quasi-Baer iffAis quasi-Baer iffAis-quasi-Baer for every extended derivationonAof δ (2)Ris δ-quasi-Baer iffAis CS-module over a ringA⊗zAop.

ISSN:0092-7872    

DOI:10.1080/00927870008827058

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor

ISSN:0092-7872    

DOI:10.1080/00927870008827059

出版商:Gordon and Breach Science Publishers Ltd.    

年代:2000

数据来源: Taylor