Tarski defined a way of assigning to each boolean algebra, B, an invariant inv(B) ∈ In, where In is a set of triples from N, such that two boolean algebras have the same invariant if and only if they are elementarily equivalent. Moreover, given the invariant of a boolean algebra, there is a computable procedure that decides its elementary theory. If we restrict our attention to dense Boolean al...

A class of recursively enumerable sets may be classified either as an object in itself — the range of a two-place function in the obvious way — or by means of the corresponding set of indices. The latter approach is not only more precise but also, as we show below, provides an alternative method for solving certain problems on recursively enumerable sets and their degrees of unsolvability. The ...

dx = F (x, y) and the wave equation from the point of view of index sets. Index sets play an important role in the study of computable functions and computably enumerable sets (see, for example, Soare [21]) . Index sets for computable combinatorics have been studied by Gasarch and others [8, 9]; the latter paper provides a survey of such results. Index sets for Π1 classes were developed by the ...

Any vertex labeling f : V → {0, 1} of the graph G = (V, E) induces a partial edge labeling f∗ : E → {0, 1} defined by f∗(uv) = f(u) if and only if f(u) = f(v). The balance index set of G is defined as {|f∗−1(0) − f∗−1(1)| : |f−1(0) − f−1(1)| ≤ 1}. In this paper, we first determine the balance index sets of rooted trees of height not exceeding two, thereby completely settling the problem for tre...

We define a family of properties on hyperhypersimple sets and show that they yield index sets at each level of the hyperarithmetical hierarchy. An extension yields a nj-complete index set. We also classify the index set of quasimaximal sets, of coinfinite r.e. sets not having an atomless superset, and of r.e. sets major in a fixed nonrecursive r.e. set. 0. Introduction. The present paper deals ...

1 Acknowledgements I would first like to thank my advisor Professor Karen Lange. She has quite literally taught me everything I know about computability. She has helped me develop as not only a math researcher, but also a writer and presenter. I would also like to thank NSF grant DMS-1100604 for funding summer research that was instrumental in helping me complete this thesis. I would also like ...

In reply to Péter Majlender, the connection between the (maximum spread) equidifferent OWA operator weights and the analytical method for the minimum variance OWA operator problem [R. Fullér, P. Majlender, On obtaining minimal variability OWA operator weights, Fuzzy Sets and Systems 136 (2003) 203–215] is pointed out and the differences between them are clarified. 2006 Elsevier Inc. All rights ...

We reformulate Mesiar’s hypothesis [Possibility measures, integration and fuzzy possibility measures, Fuzzy Sets and Systems 92 (1997) 191196], which as such was shown to be untrue by Murofushi [Two-valued possibility measures induced by σ-finite σ-additive measures, Fuzzy Sets and Systems 126 (2002) 265268]. We prove that a two-valued σ-maxitive measure can be induced by a σ-additive measure u...