Bi-isolation in the d.c.e. degrees
Guohua Wu
Source: J. Symbolic Logic Volume 69, Issue 2
(2004), 409-420.
Abstract
In this paper, we study the bi-isolation phenomena in the d.c.e. degrees and prove that there are c.e. degrees c1 < c2 and a d.c.e. degree d∈ (c1, c2) such that (c1, d) and (d, c2) contain no c.e. degrees. Thus, the c.e. degrees between c1 and c2 are all incomparable with d. We also show that there are d.c.e. degrees d1 < d2 such that (d1, d2) contains a unique c.e. degree.
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Permanent link to this document: http://projecteuclid.org/euclid.jsl/1082418534
Digital Object Identifier: doi:10.2178/jsl/1082418534
Mathematical Reviews number (MathSciNet): MR2058180
Zentralblatt MATH identifier: 1076.03028
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