摘要:

AbstractThe projection constants of thelpn-spaces for 1 ≦p≦ 2 satisfywithin the real case andin the complex case. Further, there isc<1 such that the projection constant of anyn-dimensional spaceXnwith 1-symmetric basis can be estimated by. The proofs of the results are based on averaging techniques over permutations and a variant of Khintchine's inequality which states that

ISSN:0075-4102    

DOI:10.1515/crll.1999.511.1

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

摘要:

AbstractIn this paper, we generalize to the “log regular case” a result of de Jong and Oort which states that any morphism satisfying certain conditions from the complement of a divisor with normal crossings in a regular scheme to a moduli stack of stable curves extends over the entire regular scheme. The proof uses the theory of “regular log schemes” — i.e., schemes with singularities like those of toric varieties – due to K. Kato ([12]). We then use this extension theorem to prove that under certain natural conditions any scheme which is a successive fibration of smooth hyperbolic curves may be compactified to a successive fibration of stable curves.

ISSN:0075-4102    

DOI:10.1515/crll.1999.511.43

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

摘要:

AbstractWe investigate some very general pinching results for eigensections with small eigenvalue of a Riemannian vector bundle. In particular, this gives pinching results for the eigenvalues of 1-forms on a compact Riemannian manifold, along with other applications.

ISSN:0075-4102    

DOI:10.1515/crll.1999.511.73

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

摘要:

1. IntroductionLetXbe an algebraic variety defined over a number fieldF. We will say that rational points arepotentially denseif there exists a finite extensionK/Fsuch that the set ofK-rational pointsX(K) is Zariski dense inX. The main problem is to relate this property to geometric invariants ofX. Hypothetically, on varieties of general type rational points are not potentially dense. In this paper we are interested in smooth projective varieties such that neither they nor their unramified coverings admit a dominant map onto varieties of general type. For these varieties it seems plausible to expect that rational points are potentially dense (see [2]).

ISSN:0075-4102    

DOI:10.1515/crll.1999.511.87

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

摘要:

AbstractWe show that among the infinitely many conjugacy classes of finite co-volume Kleinian groups generated by two elements of finite order, there are only finitely many which arearithmetic. In particular there are only finitely many arithmetic generalized triangle groups. This latter result generalizes a theorem of Takeuchi.

ISSN:0075-4102    

DOI:10.1515/crll.1999.511.95

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

摘要:

AbstractWe prove a fixed point theorem for twin buildings of arbitrary rank. This theorem is then used to construct certain twin buildings whose existence was conjectured in [12]. As a consequence we obtain a classification of twin buildings whose rank 2 residues correspond to split algebraic groups over a field of cardinality at least 4. A similar result follows for twin buildings whose rank 2 residues are finite.

ISSN:0075-4102    

DOI:10.1515/crll.1999.511.119

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

摘要:

AbstractWe introduce a generalized version of aq-Schur algebra (of parabolic type) for arbitrary Hecke algebras over extended Weyl groups. We describe how the decomposition matrix of a finite group with splitBN-pair, with respect to a non-describing prime, can be partially described by the decomposition matrices of suitably chosenq-Schur algebras. We show that the investigated structures occur naturally in finite groups of Lie type.

ISSN:0075-4102    

DOI:10.1515/crll.1999.511.145

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

ISSN:0075-4102    

DOI:10.1515/crll.1999.511.193

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter