On the definable ideal generated by nonbounding c.e. degrees

Liang Yu, Yue Yang
2005 Journal of Symbolic Logic (JSL)  
Let [NB]1 denote the ideal generated by nonbounding c.e. degrees and NCup the ideal of noncuppable c.e. degrees. We show that both [NB]1 ∩ NCup and the ideal generated by nonbounding and noncuppable degrees are new, in the sense that they are different from M, [NB]1 and NCup—the only three known definable ideals so far.
doi:10.2178/jsl/1107298519 fatcat:jkjw4dyfh5aihobt6iul7opiry