ON THE INTERPLAY BETWEEN EFFECTIVE NOTIONS OF RANDOMNESS AND GENERICITY.

In this paper, we study the power and limitations of computing effectively generic sequences using effectively random oracles. Previously, it was known that every 2-random sequence computes a 1-generic sequence (as shown by Kautz) and every 2-random sequence forms a minimal pair in the Turing degree...

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Detalles Bibliográficos
Publicado en:Journal of Symbolic Logic Vol. 84; no. 1; pp. 393 - 408
Autores principales: BIENVENU, LAURENT, PORTER, CHRISTOPHER P.
Formato: Artículo
Publicado: Cambridge University Press Mar2019
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Acceso en línea:Ver este registro en EBSCOhost
Descripción
Sumario:In this paper, we study the power and limitations of computing effectively generic sequences using effectively random oracles. Previously, it was known that every 2-random sequence computes a 1-generic sequence (as shown by Kautz) and every 2-random sequence forms a minimal pair in the Turing degrees with every 2-generic sequence (as shown by Nies, Stephan, and Terwijn). We strengthen these results by showing that every Demuth random sequence computes a 1-generic sequence and that every Demuth random sequence forms a minimal pair with every pb-generic sequence (where pb-genericity is an effective notion of genericity that is strictly between 1-genericity and 2-genericity). Moreover, we prove that for every comeager G ⊆ 2 , there is some weakly 2-random sequence X that computes some Y ∈ G, a result that allows us to provide a fairly complete classification as to how various notions of effective randomness interact in the Turing degrees with various notions of effective genericity.