In this paper we construct linear orderings whoseΔ 2 0 -spectra coincide with classes of all high0 and high1 degrees, respectively. We also prove that there exists a computable linear ordering such that its degree spectrum ...
We prove that a nontrivial degree spectrum of the successor relation of either strongly η-like or non-η-like computable linear orderings is closed upwards in the class of all computably enumerable degrees. We also show ...