Guohua Wu

A d.c.e. (2-computably enumerable) degree d is pseudo-isolated if d itself is non-isolated (in the sense that no computably enumerable (c.e.) degree below d can bound the c.e. degrees below d) and there is a d.c.e. degree b < d bounding all c.e. degrees below d. We prove in this paper that the pseudo-isolated degrees are densely distributed in the c.e. degrees.

2000 Mathematical Subject Classification: 03D25, 03D28.

Keywords: non-isolated degrees, pseudo-isolated degrees, density.