Functional Projection and Complexity Reduction

Vera Fischer, Yurii Khomskii, Yipu Li +1

Törnquist (arXiv:1310.3250) proved that if there exists a ${\mathbf{\Sigma }}_2^1$ maximal almost disjoint (MAD) family, then there exists a ${\mathbf{\Pi }}_1^1$ MAD family. Since then, se…