11,080 research outputs found
A Note on New Semi-Regular Divisible Difference Sets
We give a construction for new families of semi-regular divisible difference sets. The construction is a variation of McFarland\u27s scheme [5] tor noncyclic difference sets
Torsion-free, divisible, and Mittag-Leffler modules
We study (relative) K-Mittag-Leffler modules, with emphasis on the class K of
absolutely pure modules. A final goal is to describe the K-Mittag-Leffler
abelian groups as those that are, modulo their torsion part, aleph_1-free,
Cor.6.12. Several more general results of independent interest are derived on
the way. In particular, every flat K-Mittag-Leffler module (for K as before) is
Mittag-Leffler, Thm.3.9. A question about the definable subcategories generated
by the divisible modules and the torsion-free modules, resp., has been left
open, Quest.4.6
Algebraically constructible functions
An algebraic version of Kashiwara and Schapira's calculus of constructible
functions is used to describe local topological properties of real algebraic
sets, including Akbulut and King's numerical conditions for a stratified set of
dimension three to be algebraic. These properties, which include
generalizations of the invariants modulo 4, 8, and 16 of Coste and Kurdyka, are
defined using the link operator on the ring of constructible functions.Comment: AMS-TeX v2.1, 25 page
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