We consider isolation from side in the structure of 2-computably enumerable wtt-degrees. Intuitively, a 2-computably enumerable degree d is isolated from side if all computably enumerable degrees from its lower cone are bounded by some computably enumerable degree incomparable with d. We prove that any proper 2-computably enumerable wtt-degree is isolated from side by some computable enumerable wtt-degree. We show how this property can be combined with a cone avoidance.
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Yamaleev, M.M. Isolation from Side and Cone Avoidance in the 2-Computably Enumerable wtt-Degrees. J Math Sci 275, 54–65 (2023). https://doi.org/10.1007/s10958-023-06659-9
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DOI: https://doi.org/10.1007/s10958-023-06659-9