Deprecated: Function split() is deprecated in /srv/www/htdocs-cs/cie08/db-code.php on line 107

Deprecated: Function split() is deprecated in /srv/www/htdocs-cs/cie08/db-code.php on line 117
CiE 2008 - Regular Talk: - Joining to High Degrees
Computability in Europe 2008
Logic and Theory of Algorithms

## Regular Talk: Joining to High Degrees

Edit abstract data

Notice: Use of undefined constant session - assumed 'session' in /srv/www/htdocs-cs/cie08/conf-code.php on line 440

Notice: Use of undefined constant slot - assumed 'slot' in /srv/www/htdocs-cs/cie08/conf-code.php on line 441

Notice: Use of undefined constant room - assumed 'room' in /srv/www/htdocs-cs/cie08/conf-code.php on line 442
 Speaker: Jiang Liu Author(s): Guohua Wu and Jiang Liu Slot: Thu, 11:20-11:40, Room 24 (col. 3)

### Abstract

Cholak, Groszek and Slaman proved that there is a nonzero computably enumerable (c.e.) degree cupping every low c.e. degree to a low c.e. degree. In the same paper, they pointed out that every nonzero c.e. degree can cup a low$_2$ c.e. degree to a nonlow$_2$ degree. Later, Jockusch, Li and Yang improved the latter result by showing that every nonzero c.e. degree $\mathbf{c}$ is cuppable to a high c.e. degree by a low$_{2}$ c.e. degree $\mathbf{b}$. It is natural to ask in which subclass of low$_2$ c.e. degrees can $\mathbf{b}$ in Jockusch, Li and Yang's result be located in. Wu improved that $\mathbf{b}$ can be cappable. We prove in this paper that ${\bf b}$ can even be noncuppable, improving both Jockusch, Li and Yang, and Wu's results.

 websites: Arnold Beckmann Warning: date(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected the timezone 'UTC' for now, but please set date.timezone to select your timezone. in /srv/www/htdocs-cs/cie08/conf-code.php on line 136 2008-06-03