منابع مشابه
Generalized R-Cohesiveness and The Arithmetical Hierarchy: A Correction to "Generalized Cohesiveness"
ForX ⊆ ω, let [X] denote the class of all n-element subsets of X. An infinite set A ⊆ ω is called n-r-cohesive if for each computable function f : [ω] → {0, 1} there is a finite set F such that f is constant on [A−F ]. We show that for each n ≥ 2 there is no Πn set A ⊆ ω which is n-r-cohesive. For n = 2 this refutes a result previously claimed by the authors, and for n ≥ 3 it answers a question...
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We study some generalized notions of cohesiveness which arise naturally in connection with effective versions of Ram-sey's Theorem. An infinite set A of natural numbers is n–cohesive (respectively, n–r–cohesive) if A is almost homogeneous for every computably enumerable (respectively, computable) 2–coloring of the n–element sets of natural numbers. (Thus the 1–cohesive and 1–r–cohesive sets coi...
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It is characteristic of a continuum that it be “all of one piece”, in the sense of being inseparable into two (or more) disjoint nonempty parts. By taking “part” to mean open (or closed) subset of the space, one obtains the usual topological concept of connectedness. Thus a space S is defined to be connected if it cannot be partitioned into two disjoint nonempty open (or closed) subsets – or eq...
متن کاملCohesiveness in promise problems
Promise problems have been introduced in 1985 by S.Even e.a. as a generalization of decision problems. Using a very general approach we study solvability and unsolvability conditions for promise problems of set families and languages. We show, that cores of unsolvability are completely determined by partitions of cohesive sets. We prove the existence of cores in unsolvable promise problems assu...
متن کاملUnearthed: The Other Side of Group Cohesiveness
One of the most consistently studied constructs in group dynamics research is Cohesiveness. It is a fact, that there is a tendency to see the effects of group cohesiveness as being largely positive. The periodic review of cohesiveness–performance relation had been positive. However, not much attention has been devoted to the fact that group cohesiveness can be detrimental to the group performan...
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ژورنال
عنوان ژورنال: The Journal of Symbolic Logic
سال: 1999
ISSN: 0022-4812,1943-5886
DOI: 10.2307/2586482