منابع مشابه
Thin Coverings of Modules
Thin coverings are a method of constructing graded-simple modules from simple (ungraded) modules. After a general discussion, we classify the thin coverings of (quasifinite) simple modules over associative algebras graded by finite abelian groups. The classification uses the representation theory of cyclotomic quantum tori. We close with an application to representations of multiloop Lie algebras.
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Let t(n, d) be the minimum number t such that there are t of the n lattice points {(x1, . . . , xd) : 1 ≤ xi ≤ n} so that the ( t 2 ) lines that they determine cover all the above n lattice points. We prove that for every integer d ≥ 2 there are two positive constants c1 = c1(d) and c2 = c2(d) such that for every n c1n d(d−1)/(2d−1) ≤ t(n, d) ≤ c2n log n. The special case d = 2 settles a proble...
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The minimum number of k-subsets out of a v-set such that each t-set is contained in at least one k-set is denoted by C (v; k; t). In this paper, a computer search for nding good such covering designs, leading to new upper bounds on C (v; k; t), is considered. The search is facilitated by predetermining automorphisms of desired covering designs. A stochastic heuristic search (embedded in the gen...
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In the thesis we study selected properties of random coverings of graphs introduced by Amit and Linial in 2002. A random n-covering of a graph G, denoted by G̃, is obtained by replacing each vertex v of G by an n-element set G̃v and then choosing, independently for every edge e = {x, y} ∈ E(G), uniformly at random a perfect matching between G̃x and G̃y. The first problem we consider is the typical ...
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ژورنال
عنوان ژورنال: Arkiv för Matematik
سال: 1985
ISSN: 0004-2080
DOI: 10.1007/bf02384391