Geodesic
Definable hereditary families in the projective hierarchy
Fundamenta Mathematicae, Tome 140 (1991) no. 2, pp. 183-189

Voir la notice de l'article provenant de la source Institute of Mathematics Polish Academy of Sciences

We show that if ℱ is a hereditary family of subsets of $ω^ω$ satisfying certain definable conditions, then the $Δ_1^1$ reals are precisely the reals α such that ${β:α ∈ Δ_1^1(β)} ∉ ∈ ℱ$. This generalizes the results for measure and category. Appropriate generalization to the higher levels of the projective hierarchy is obtained under Projective Determinacy. Application of this result to the $Q_{2n+1}$-encodable reals is also shown.
DOI : 10.4064/fm-140-2-183-189

R. Barua 1 ; V. Srivatsa 1

1 
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R. Barua; V. Srivatsa. Definable hereditary families in the projective hierarchy. Fundamenta Mathematicae, Tome 140 (1991) no. 2, pp. 183-189. doi: 10.4064/fm-140-2-183-189

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