Asymptotic density and the Ershov hierarchy

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Downey, Rod; Jockusch, Carl; McNicholl, Timothy H.; Schupp, Paul;
  • Subject: Mathematics - Logic | 03D25, 03D78

We classify the asymptotic densities of the $\Delta^0_2$ sets according to their level in the Ershov hierarchy. In particular, it is shown that for $n \geq 2$, a real $r \in [0,1]$ is the density of an $n$-c.e.\ set if and only if it is a difference of left-$\Pi_2^0$ re... View more
  • References (11)
    11 references, page 1 of 2

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    9. R. Soare, Cohesive sets and recursively enumerable Dedekind cuts, Pacific J. Math. 31 (1969), 215-231. School of Mathematics, Statistics, and Operations Research, Victoria University of Wellington, New Zealand E-mail address: Department of Mathematics, University of Illinois at Urbana-Champaign, 1409 W.

    Green St., Urbana, Illinois 61801 USA E-mail address: Department of Mathematics, University of Illinois at Urbana-Champaign, 1409 W.

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