Isolation and the Jump Operator
by
Guohua Wu
School of Mathematical and Computing Sciences, Victoria University of Wellington

A d.c.e. degree d is isolated by a c.e. degree a, if a < d is the greatest c.e. degree below d. One would have the impression that if d is isolated by a, then d would be close to a, since there is no c.e. degree between d and a. In this paper, we show that this is not true in terms of the jump operator:

Theorem: There is a high d.c.e. degree isolated by a low₂ c.e. degree.

Date received: September 20, 2000

Copyright © 2000 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caek-18.