Complete, Recursively Enumerable Relations in Arithmetic
β Scribed by Giovanna D'Agostino; Mario Magnago
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 489 KB
- Volume
- 41
- Category
- Article
- ISSN
- 0044-3050
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β¦ Synopsis
Abstract
Using only propositional connectives and the provability predicate of a Ξ£~1~βsound theory T containing Peano Arithmetic we define recursively enumerable relations that are complete for specific natural classes of relations, as the class of all r. e. relations, and the class of all strict partial orders. We apply these results to give representations of these classes in T by means of formulas.
π SIMILAR VOLUMES
## Abstract We show that that every countable model of __PA__ has a conservative extension __M__ with a subset __Y__ such that a certain Ξ£~1~(__Y__)βformula defines in __M__ a subset which is not r. e. relative to __Y__.
## Abstract I introduce an effective enumeration of all effective enumerations of classes of r. e. sets and define with this the index set __IE__ of injectively enumerable classes. It is easy to see that this set is β~5~ in the Arithmetical Hierarchy and I describe a proof for the β~5~βhardness of
## Abstract The paper characterizes the second order arithmetic theorems of a set theory that features a recursively Mahlo universe; thereby complementing prior proofβtheoretic investigations on this notion. It is shown that the property of being recursively Mahlo corresponds to a certain kind of Ξ²