#### Filter Results:

#### Publication Year

2005

2016

#### Publication Type

#### Co-author

#### Key Phrase

#### Publication Venue

Learn More

- Thomas F Kent, Steffen Lempp, Jerome Keisler, Ken Kunen, Arnie Miller, Patrick Speissegger +3 others
- 2005

Enumeration reducibility was introduced by Friedberg and Rogers in 1959 as a positive reducibility between sets. The enumeration degrees provide a wider context in which to view the Turing degrees by allowing us to use any set as an oracle instead of just total functions. However, in spite of the fact that there are several applications of enumeration… (More)

For any enumeration degree a let D s a be the set of s-degrees contained in a. We answer an open question of Watson by showing that if a is a nontrivial Σ 0 2-enumeration degree, then D s a has no least element. We also show that every countable partial order embeds into D s a. Finally, we construct Σ 0 2-sets A and B such that B ≤ e A but for every X ≡ e… (More)

For any enumeration degree a let D s a be the set of s-degrees contained in a. We answer an open question of Watson by showing that if a is a nontrivial Σ 0 2-enumeration degree, then D s a has no least element. We also show that every countable partial order embeds into D s a .

- ‹
- 1
- ›