Published online by Cambridge University Press: 18 August 2014
The K-trivial sets form an ideal in the Turing degrees, which isgenerated by its computably enumerable (c.e.) members and has an exact pairbelow the degree of the halting problem. The question of whether it has an exactpair in the c.e. degrees was first raised in [22, Question 4.2] and later in[25, Problem 5.5.8].
We give a negative answer to this question. In fact, we show the followingstronger statement in the c.e. degrees. There exists aK-trivial degree d such that for all degreesa, b which are not K-trivial and a> d, b > d there exists a degree vwhich is not K-trivial and a > v, b >v. This work sheds light to the question of the definability of theK-trivial degrees in the c.e. degrees.