Results 261 to 270 of about 2,213,198 (296)
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Computability, 2011
A set is called r-closed left-r.e. iff every set r-reducible to it is also a left-r.e. set. It is shown that some but not all left-r.e. cohesive sets are many–one closed left-r.e. sets. Ascending reductions are many–one reductions via an ascending function; left-r.e. cohesive sets are also ascending closed left-r.e. sets.
Sanjay Jain 0001 +2 more
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A set is called r-closed left-r.e. iff every set r-reducible to it is also a left-r.e. set. It is shown that some but not all left-r.e. cohesive sets are many–one closed left-r.e. sets. Ascending reductions are many–one reductions via an ascending function; left-r.e. cohesive sets are also ascending closed left-r.e. sets.
Sanjay Jain 0001 +2 more
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2009
The notion of immune sets is extended to closed sets and $\Pi^0_1$ classes in particular. We construct a $\Pi^0_1$ class with no computable member which is not immune. We show that for any computably inseparable sets A and B , the class S (A ,B ) of separating sets for A and B is immune. We show that every perfect thin $\Pi^0_1$ class is immune.
Douglas Cenzer, Rebecca Weber, Guohua Wu
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The notion of immune sets is extended to closed sets and $\Pi^0_1$ classes in particular. We construct a $\Pi^0_1$ class with no computable member which is not immune. We show that for any computably inseparable sets A and B , the class S (A ,B ) of separating sets for A and B is immune. We show that every perfect thin $\Pi^0_1$ class is immune.
Douglas Cenzer, Rebecca Weber, Guohua Wu
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Combinatorica, 1984
A subset T of the node set V of a digraph \(G=(V,E)\) is called path-closed if for each v,v'\(\in T\) all nodes lying on directed paths from v to v' also belong to T. The author characterizes the convex hull of the incidence vectors of all path-closed sets by a set of linear inequalities thus turning the problem of finding a maximum path-closed set (in
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A subset T of the node set V of a digraph \(G=(V,E)\) is called path-closed if for each v,v'\(\in T\) all nodes lying on directed paths from v to v' also belong to T. The author characterizes the convex hull of the incidence vectors of all path-closed sets by a set of linear inequalities thus turning the problem of finding a maximum path-closed set (in
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On the ultrafilter of closed, unbounded sets
Journal of Symbolic Logic, 1979Solovay proved in 1967 that the axiom of determinateness implies that the filter C generated by closed and unbounded subsets of ω1 is an ultrafilter. It has long been conjectured that a significant part of the theory of the axiom of determinateness should be provable from the hypothesis that C is an ultrafilter, but even the first step of finding inner
D. A. Martin, William John Mitchell
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Combinatorica, 2005
A smallest separator in a finite, simple, undirected graph G is a set S ⊆ V (G) such that G–S is disconnected and |S|=κ(G), where κ(G) denotes the connectivity of G.A set S of smallest separators in G is defined to be closed if for every pair S,T ∈ S, every component C of G–S, and every component S of G–T intersecting C either X(C,D) := (V (C) ∩ T ...
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A smallest separator in a finite, simple, undirected graph G is a set S ⊆ V (G) such that G–S is disconnected and |S|=κ(G), where κ(G) denotes the connectivity of G.A set S of smallest separators in G is defined to be closed if for every pair S,T ∈ S, every component C of G–S, and every component S of G–T intersecting C either X(C,D) := (V (C) ∩ T ...
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Covering analytic sets by families of closed set
Journal of Symbolic Logic, 1994AbstractWe prove that for every familyIof closed subsets of a Polish space eachset can be covered by countably many members ofIor else contains a nonemptyset which cannot be covered by countably many members ofI. We prove an analogous result forκ-Souslin sets and show that ifA#exists for anyA⊂ωω, then the above result is true forsets.
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The Journal of Clinical Ethics, 2011
Published accounts of specific priority-setting projects in healthcare are relatively few. This article chronicles the collaborative efforts of a professional practice lead and a bioethicist to strengthen the priority-setting process for a specific home care service.
Barbara, Russell, Deb, deVlaming
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Published accounts of specific priority-setting projects in healthcare are relatively few. This article chronicles the collaborative efforts of a professional practice lead and a bioethicist to strengthen the priority-setting process for a specific home care service.
Barbara, Russell, Deb, deVlaming
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The Journal of Symbolic Logic, 1976
The extreme interest of set theorists in the notion of “closed unbounded set” is epitomized in the following well-known theorem:Theorem A. For any regular cardinal κ > ω, the intersection of any two closed unbounded subsets of κ is closed and unbounded.The proof of this theorem is easy and in fact yields a stronger result, namely that for any ...
James E. Baumgartner +2 more
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The extreme interest of set theorists in the notion of “closed unbounded set” is epitomized in the following well-known theorem:Theorem A. For any regular cardinal κ > ω, the intersection of any two closed unbounded subsets of κ is closed and unbounded.The proof of this theorem is easy and in fact yields a stronger result, namely that for any ...
James E. Baumgartner +2 more
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Journal of Symbolic Logic, 1983
AbstractWe discuss the problem of finding forcing posets which introduce closed unbounded subsets to a given stationary set.
Uri Abraham, Saharon Shelah
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AbstractWe discuss the problem of finding forcing posets which introduce closed unbounded subsets to a given stationary set.
Uri Abraham, Saharon Shelah
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On the Sum of Roots of a Closed Set
Journal of Mathematical Sciences, 2004zbMATH Open Web Interface contents unavailable due to conflicting licenses.
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