منابع مشابه
Quasi-projective covers of right $S$-acts
In this paper $S$ is a monoid with a left zero and $A_S$ (or $A$) is a unitary right $S$-act. It is shown that a monoid $S$ is right perfect (semiperfect) if and only if every (finitely generated) strongly flat right $S$-act is quasi-projective. Also it is shown that if every right $S$-act has a unique zero element, then the existence of a quasi-projective cover for each right act implies that ...
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We discuss properties of complex algebraic orbifold groups, their characteristic varieties, and their abelian covers. In particular, we deal with the question of (quasi)-projectivity of orbifold groups. We also prove a structure theorem for the variety of characters of normalcrossing quasi-projective orbifold groups. Finally, we extend Sakuma’s formula for the first Betti number of abelian cove...
متن کاملquasi-projective covers of right $s$-acts
in this paper $s$ is a monoid with a left zero and $a_s$ (or $a$) is a unitary right $s$-act. it is shown that a monoid $s$ is right perfect (semiperfect) if and only if every (finitely generated) strongly flat right $s$-act is quasi-projective. also it is shown that if every right $s$-act has a unique zero element, then the existence of a quasi-projective cover for each right act implies that ...
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In this paper we present linear time approximation schemes for several generalized matching problems on nonbipartite graphs. Our results include O (m)-time algorithms for (1 − )maximum weight f -factor and (1+ )-approximate minimum weight f -edge cover. As a byproduct, we also obtain direct algorithms for the exact cardinality versions of these problems running in O(m √ f(V )) time. The technic...
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We introduce the notion of path extensions of tiling semigroups and investigate their properties. We show that the path extension of a tiling semigroup yields a strongly F *-inverse cover of the tiling semigroup and that it is isomorphic to an HNN * extension of its semilattice of idempo-tents.
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ژورنال
عنوان ژورنال: The Pure and Applied Mathematics
سال: 2013
ISSN: 1226-0657
DOI: 10.7468/jksmeb.2013.20.2.103