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A STRUCTURAL DICHOTOMY IN THE ENUMERATION DEGREES

Published online by Cambridge University Press:  10 July 2020

HRISTO A. GANCHEV
Affiliation:
FACULTY OF MATHEMATICS AND INFORMATICS SOFIA UNIVERSITY 5 JAMES BOURCHIER BLVD., SOFIA 1164, BULGARIAE-mail: ganchev@fmi.uni-sofia.bg
ISKANDER SH. KALIMULLIN
Affiliation:
N.I. LOBACHEVSKY INSTITUTE OF MATHEMATICS AND MECHANICS KAZAN (VOLGA REGION) FEDERAL UNIVERSITY UL. KREMLEVSKAYA 18, KAZAN, TATARSTAN 420008, RUSSIAN FEDERATIONE-mail: Iskander.Kalimullin@kpfu.ru
JOSEPH S. MILLER
Affiliation:
DEPARTMENT OF MATHEMATICS UNIVERSITY OF WISCONSIN–MADISON 480 LINCOLN DR., MADISON, WI53706, USAE-mail: jmiller@math.wisc.eduE-mail: msoskova@math.wisc.edu
MARIYA I. SOSKOVA
Affiliation:
DEPARTMENT OF MATHEMATICS UNIVERSITY OF WISCONSIN–MADISON 480 LINCOLN DR., MADISON, WI53706, USAE-mail: jmiller@math.wisc.eduE-mail: msoskova@math.wisc.edu

Abstract

We give several new characterizations of the continuous enumeration degrees. The main one proves that an enumeration degree is continuous if and only if it is not half of a nontrivial relativized $\mathcal {K}$ -pair. This leads to a structural dichotomy in the enumeration degrees.

Type
Article
Copyright
© The Author(s), 2020. Published by Cambridge University Press on behalf of The Association for Symbolic Logic

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