Intervals without Critical Triples [chapter]

P. Cholak, R. Downey, R. Shore, Johann A. Makowsky, Elena V. Ravve
Logic Colloquium '95  
This paper is concerned with the construction of intervals of computably enumerable degrees in which the lattice M 5 (see Figure 1 ) cannot be embedded. Actually, w e construct intervals I of computably enumerable degrees without any w eak critical triples (this implies that M 5 cannot be embedded in I, see Section 2). Our strongest result is that there is a low 2 computably enumerable degree e such that there are no weak critical triples in either of the intervals 0 e] o r e 0 0 ]. 1991 Mathematics Subject Classi cation. Primary 03D25.
doi:10.1017/9781316716830.005 fatcat:bfgdnxc3ljchjijc3d3fe2augi