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991.
A. Lanteri 《Journal of Pure and Applied Algebra》2008,212(4):808-831
Let (X,L,V) be a triplet where X is an irreducible smooth complex projective variety, L is an ample and spanned line bundle on X and V⊆H0(X,L) spans L. The discriminant locus D(X,V)⊂|V| is the algebraic subset of singular elements of |V|. We study the components of D(X,V) in connection with the jumping sets of (X,V), generalizing the classical biduality theorem. We also deal with the degree of the discriminant (codegree of (X,L,V)) giving some bounds on it and classifying curves and surfaces of codegree 2 and 3. We exclude the possibility for the codegree to be 1. Significant examples are provided. 相似文献
992.
Matilde N. Lalín 《Journal of Number Theory》2008,128(5):1231-1271
In this work we apply the techniques that were developed in [M.N. Lalín, An algebraic integration for Mahler measure, Duke Math. J. 138 (2007), in press] in order to study several examples of multivariable polynomials whose Mahler measure is expressed in terms of special values of the Riemann zeta function or Dirichlet L-series. The examples may be understood in terms of evaluations of regulators. Moreover, we apply the same techniques to the computation of generalized Mahler measures, in the sense of Gon and Oyanagi [Y. Gon, H. Oyanagi, Generalized Mahler measures and multiple sine functions, Internat. J. Math. 15 (5) (2004) 425-442]. 相似文献
993.
Here, we construct infinitely many number fields of any given degree d>1 whose class numbers have many prime factors. 相似文献
994.
Gerald Beer 《Topology and its Applications》2008,155(6):503-514
Call a sequence in a metric space cofinally Cauchy if for each positive ε there exists a cofinal (rather than residual) set of indices whose corresponding terms are ε-close. We give a number of new characterizations of metric spaces for which each cofinally Cauchy sequence has a cluster point. For example, a space has such a metric if and only each continuous function defined on it is uniformly locally bounded. A number of results exploit a measure of local compactness functional that we introduce. We conclude with a short proof of Romaguera's Theorem: a metrizable space admits such a metric if and only if its set of points having a compact neighborhood has compact complement. 相似文献
995.
Bruce W. Tattershall Kathryn E. Holmes Catherine Tweedy Gina C. Valks 《无机化学与普通化学杂志》2008,634(10):1703-1710
Reaction of a mixture of bicyclic phosphorus sulfide selenide iodides α‐P4SnSe3−nI2 (n = 0–3) with PriNH2 and Et3N gave corresponding diamides α‐P4SnSe3−n(NHPri)2 (n = 0–3) and imides α‐P4SnSe3−n(μ‐NPri) (n = 2–3), identified in solution by 31P NMR. In one isomer of α‐P4S2Se(μ‐NPri), the C2 symmetry of imides such as α‐P4S3(μ‐NPri) was broken, allowing relative assignment of 2J NMR couplings to the PNP bridge and the PSP bridge opposite to it. The coupling through the sulfur bridge was found to be reduced to ca. zero, in contrast to previous assumptions for this class of compounds. Ab initio models were calculated at the MPW1PW91/svp level for the sulfide selenide imides and for a selection of bond rotamers of the diamides, and at the MPW1PW91/LanL2DZ(d) level for the sulfide selenide diiodides. Different skeletal isomers were prevalent for the mixed chalcogenide diamides than for the diiodides, showing that exchange of chalcogen between skeletal positions took place in the amination reaction even at room temperature. Similar differences to those observed were predicted by the models, suggesting that equilibrium was attained. 相似文献
996.
We prove a relative version of the theorem of Webb that the augmented chain complex of the p-subgroup complex of a finite group, considered as a complex of modules for the group, is homotopy equivalent to a complex of projectives. This allows us to take into account the group of automorphisms of the group. 相似文献
997.
Mitrofan M. Choban 《Topology and its Applications》2008,155(8):787-796
In the present article many theorems about existence of continuous selections for a set-valued mapping into the metrizable spaces are extended to mappings into non-metrizable spaces. 相似文献
998.
We show that extensions of algebraically closed fields induce full and faithful functors between the respective motivic stable
homotopy categories with finite coefficients. 相似文献
999.
Warren Wm. McGovern 《Journal of Pure and Applied Algebra》2008,212(2):340-348
Elementary divisor domains were defined by Kaplansky [I. Kaplansky, Elementary divisors and modules, Trans. Amer. Math. Soc. 66 (1949) 464-491] and generalized to rings with zero-divisors by Gillman and Henriksen [L. Gillman, M. Henriksen, Some remarks about elementary divisor rings, Trans. Amer. Math. Soc. 82 (1956) 362-365]. In [M.D. Larsen, W.J. Lewis, T.S. Shores, Elementary divisor rings and finitely presented modules, Trans. Amer. Math. Soc. 187 (1) (1974) 231-248], it was also proved that if a Hermite ring satisfies (N), then it is an elementary divisor ring. The aim of this article is to generalize this result (as well as others) to a much wider class of rings. Our main result is that Bézout rings whose proper homomorphic images all have stable range 1 (in particular, neat rings) are elementary divisor rings. 相似文献
1000.
Ahmed Ayache 《Journal of Pure and Applied Algebra》2008,212(10):2176-2181
We establish in this paper a result that gives the number of intermediary rings between R and S where (R,S) is a normal pair of rings. This result answers in particular a question which was left open in [A. Jaballah, Finiteness of the set of intermediary rings in a normal pair, Saintama Math. J. 17 (1999) 59-61]. Further applications are also given. 相似文献