Journal of Symbolic Logic

Bi-isolation in the d.c.e. degrees

Guohua Wu

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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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J. Symbolic Logic, Volume 69, Issue 2 (2004), 409-420.

First available in Project Euclid: 19 April 2004

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Wu, Guohua. Bi-isolation in the d.c.e. degrees. J. Symbolic Logic 69 (2004), no. 2, 409--420. doi:10.2178/jsl/1082418534.

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