Normal numbers and the Borel hierarchy
Verónica Becher, Pablo Ariel Heiber, Theodore A. Slaman (2014)
Fundamenta Mathematicae
Similarity:
We show that the set of absolutely normal numbers is Π⁰₃-complete in the Borel hierarchy of subsets of real numbers. Similarly, the set of absolutely normal numbers is Π⁰₃-complete in the effective Borel hierarchy.