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ON UNIVERSAL COVERINGS OF LIE TORI
"... Abstract. In this paper we give an introduction to the theory of universal central extensions of perfect Lie algebras. In particular, we will provide a model for the universal coverings of Lie tori and we show that automorphisms and derivations lift to the universal coverings. We also prove that th ..."
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Abstract. In this paper we give an introduction to the theory of universal central extensions of perfect Lie algebras. In particular, we will provide a model for the universal coverings of Lie tori and we show that automorphisms and derivations lift to the universal coverings. We also prove
THE LEBESGUE UNIVERSAL COVERING PROBLEM
 JOURNAL OF COMPUTATIONAL GEOMETRY
, 2015
"... In 1914 Lebesgue defined a ‘universal covering’ to be a convex subset of the plane that contains an isometric copy of any subset of diameter 1. His challenge of finding a universal covering with the least possible area has been addressed by various mathematicians: Pál, Sprague and Hansen have each ..."
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In 1914 Lebesgue defined a ‘universal covering’ to be a convex subset of the plane that contains an isometric copy of any subset of diameter 1. His challenge of finding a universal covering with the least possible area has been addressed by various mathematicians: Pál, Sprague and Hansen have
Isometries, rigidity and universal covers
, 2008
"... The goal of this paper is to describe all closed, aspherical Riemannian manifolds M whose universal covers ˜ M have have a nontrivial amount of symmetry. By this we mean that Isom ( ˜ M) is not discrete. By the wellknown theorem of MyersSteenrod [MS], this condition is equivalent to [Isom ( ˜ M) ..."
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Cited by 16 (3 self)
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The goal of this paper is to describe all closed, aspherical Riemannian manifolds M whose universal covers ˜ M have have a nontrivial amount of symmetry. By this we mean that Isom ( ˜ M) is not discrete. By the wellknown theorem of MyersSteenrod [MS], this condition is equivalent to [Isom ( ˜ M
Hausdorff Convergence and Universal Covers
 Transactions of the American Mathematical Society
"... We prove that if Y is the GromovHausdorff limit of a sequence of compact manifolds, M n i, with a uniform lower bound on Ricci curvature and a uniform upper bound on diameter, then Y has a universal cover. We then show that, for i sufficiently large, the fundamental group of Mi has a surjective hom ..."
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Cited by 26 (16 self)
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We prove that if Y is the GromovHausdorff limit of a sequence of compact manifolds, M n i, with a uniform lower bound on Ricci curvature and a uniform upper bound on diameter, then Y has a universal cover. We then show that, for i sufficiently large, the fundamental group of Mi has a surjective
BRANCHING IN THE UNIVERSAL COVER OF TAUT
"... We study the topology of codimension one taut foliations of closed orientable 3manifolds which are smooth along the leaves. In particular, we focus on the lifts of these foliations to the universal cover, specifically when any set of leaves corresponding to nonseparable points in the leaf space can ..."
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We study the topology of codimension one taut foliations of closed orientable 3manifolds which are smooth along the leaves. In particular, we focus on the lifts of these foliations to the universal cover, specifically when any set of leaves corresponding to nonseparable points in the leaf space
Universal Coverings of Orthogonal Groups
 Adv. Appl. Clifford Algebras
"... Universal coverings of the orthogonal groups and their extensions are studied in terms of CliffordLipschitz groups. An algebraic description of basic discrete symmetries (space inversion P, time reversal T, charge conjugation C and their combinations PT, CP, CT, CPT) is given. Discrete subgroups {1 ..."
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Cited by 6 (5 self)
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Universal coverings of the orthogonal groups and their extensions are studied in terms of CliffordLipschitz groups. An algebraic description of basic discrete symmetries (space inversion P, time reversal T, charge conjugation C and their combinations PT, CP, CT, CPT) is given. Discrete subgroups
A Threshold of ln n for Approximating Set Cover
 JOURNAL OF THE ACM
, 1998
"... Given a collection F of subsets of S = f1; : : : ; ng, set cover is the problem of selecting as few as possible subsets from F such that their union covers S, and max kcover is the problem of selecting k subsets from F such that their union has maximum cardinality. Both these problems are NPhar ..."
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Cited by 778 (5 self)
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Given a collection F of subsets of S = f1; : : : ; ng, set cover is the problem of selecting as few as possible subsets from F such that their union covers S, and max kcover is the problem of selecting k subsets from F such that their union has maximum cardinality. Both these problems are NP
Comparing universal covers in polynomial time
"... Abstract. The universal cover TG of a connected graph G is the unique (possible infinite) tree covering G, i.e., that allows a locally bijective homomorphism from TG to G. Universal covers have major applications in the area of distributed computing. It is wellknown that if a graph G covers a graph ..."
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Abstract. The universal cover TG of a connected graph G is the unique (possible infinite) tree covering G, i.e., that allows a locally bijective homomorphism from TG to G. Universal covers have major applications in the area of distributed computing. It is wellknown that if a graph G covers a
Towards Universal Cover Decoding
"... Low complexity decoding of lowdensity paritycheck (LDPC) codes may be obtained from the application of iterative messagepassing decoding algorithms to the bipartite Tanner graph of the code. Arguably, ..."
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Cited by 4 (4 self)
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Low complexity decoding of lowdensity paritycheck (LDPC) codes may be obtained from the application of iterative messagepassing decoding algorithms to the bipartite Tanner graph of the code. Arguably,
Results 1  10
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2,039,366