Definable Davies' theorem
Volume 205 / 2009
Fundamenta Mathematicae 205 (2009), 77-89
MSC: Primary 03E15.
DOI: 10.4064/fm205-1-4
Abstract
We prove the following descriptive set-theoretic analogue of a theorem of R.~O.~Davies: Every $\Sigma^1_2$ function $f:\mathbb R\times\mathbb R\to\mathbb R$ can be represented as a sum of rectangular $\Sigma^1_2$ functions if and only if all reals are constructible.
