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Turing degrees and the Ershov hierarchy
 in Proceedings of the Tenth Asian Logic Conference, Kobe, Japan, 16 September 2008, World Scienti…c
"... Abstract. An nr.e. set can be defined as the symmetric difference of n recursively enumerable sets. The classes of these sets form a natural hierarchy which became a wellstudied topic in recursion theory. In a series of groundbreaking papers, Ershov generalized this hierarchy to transfinite level ..."
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Abstract. An nr.e. set can be defined as the symmetric difference of n recursively enumerable sets. The classes of these sets form a natural hierarchy which became a wellstudied topic in recursion theory. In a series of groundbreaking papers, Ershov generalized this hierarchy to transfinite
Domain Theory
 Handbook of Logic in Computer Science
, 1994
"... Least fixpoints as meanings of recursive definitions. ..."
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Least fixpoints as meanings of recursive definitions.
ON Σ1STRUCTURAL DIFFERENCES AMONG ERSHOV HIERARCHIES
"... Abstract. We show that the structure R of recursively enumerable degrees is not a Σ1elementary substructure of Dn, where Dn (n> 1) is the structure of nr.e. degrees in Ershov hierarchy. 1. ..."
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Abstract. We show that the structure R of recursively enumerable degrees is not a Σ1elementary substructure of Dn, where Dn (n> 1) is the structure of nr.e. degrees in Ershov hierarchy. 1.
Technical Change, Inequality, and The Labor Market
 Journal of Economic Literature
, 2002
"... This essay discusses the effect of technical change on wage inequality. I argue that the behavior of wages and returns to schooling indicates that technical change has been skillbiased during the past sixty years. Furthermore, the recent increase in inequality is most likely due to an acceleration ..."
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This essay discusses the effect of technical change on wage inequality. I argue that the behavior of wages and returns to schooling indicates that technical change has been skillbiased during the past sixty years. Furthermore, the recent increase in inequality is most likely due to an acceleration in skill bias. In contrast to twentiethcentury developments, much of thr technical change during the early nineteenth century appears to be skillreplacing. I suggest that this is because the increased supply of unskilled workers in the English cities made the introduction of these technologies profitable. On the other hand, the twentieth century has been characterized by skillbiased technical change because the rapid increase in the supply of skilled workers has induced the development of skillcomplementary technologies. The recent acceleration in skill bias is in turn likely to have been a response to the acceleration in the supply of skills during the past several decades.
Turing Definability in the Ershov Hierarchy
, 1974
"... We obtain the first nontrivial d.c.e. Turing approximation to the class of computably enumerable (c.e.) degrees. This depends on the following extension of the splitting theorem for the d.c.e. degrees: For any d.c.e. degree a, any c.e. degree b, if b < a, then there are d.c.e. degrees x 0 , x 1 s ..."
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of the Ershov hierarchy does Turing definability of given lower levels of the hierarchy occur? In particular, are the computably enumerable (c.e.) degrees E E E definable within the class of d.c.e. (= 2c.e.) degrees E E E 2 ? An important step towards a positive answer to this latter question
Asymptotic density and the Ershov hierarchy, in preparation
"... Abstract. We classify the asymptotic densities of the ∆02 sets according to their level in the Ershov hierarchy. In particular, it is shown that for n ≥ 2, a real r ∈ [0, 1] is the density of an nc.e. set if and only if it is a difference of leftΠ02 reals. Further, we show that the densities of th ..."
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Abstract. We classify the asymptotic densities of the ∆02 sets according to their level in the Ershov hierarchy. In particular, it is shown that for n ≥ 2, a real r ∈ [0, 1] is the density of an nc.e. set if and only if it is a difference of leftΠ02 reals. Further, we show that the densities
On Genericity and Ershov's Hierarchy
 MATHEMATICAL LOGIC QUARTERLY
, 1999
"... It is natural to wish to study miniaturisations of Cohen forcing suitable to sets of low arithmetic complexity. We consider extensions of the work of Schaeffer[9] and Jockusch and Posner[6] by looking at genericity notions within the ∆2 sets. Different ..."
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It is natural to wish to study miniaturisations of Cohen forcing suitable to sets of low arithmetic complexity. We consider extensions of the work of Schaeffer[9] and Jockusch and Posner[6] by looking at genericity notions within the ∆2 sets. Different
ELEMENTARY DIFFERENCES AMONG FINITE LEVELS OF THE ERSHOV HIERARCHY
"... Abstract. We study the differences among finite levels of the Ershov hierarchies. We also give a brief survey on the current state of this area. Some questions are raised. 1. Preliminary Putnam [9] is the first one who introduced the nr.e. sets. Definition 1.1. (i) A set A is nr.e. if there is a r ..."
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Abstract. We study the differences among finite levels of the Ershov hierarchies. We also give a brief survey on the current state of this area. Some questions are raised. 1. Preliminary Putnam [9] is the first one who introduced the nr.e. sets. Definition 1.1. (i) A set A is nr.e. if there is a
Results 1  10
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