An effective classification of Borel Wadge classes
Adam Day
University of Auckland, Auckland, New ZealandNoam Greenberg
Victoria University of Wellington, Wellington, New ZealandMatthew Harrison-Trainor
University of Illinois Chicago, Chicago, USADan Turetsky
Victoria University of Wellington, Wellington, New Zealand

Abstract
We give a new and effective classification of all Borel Wadge classes of subsets of Baire space . This relies on the true stage machinery originally developed by Montalbán. We use this machinery to give a new proof of Louveau and Saint Raymond’s separation theorem for Borel Wadge classes. This gives a proof of Borel Wadge determinacy in the subsystem of second-order arithmetic.
Cite this article
Adam Day, Noam Greenberg, Matthew Harrison-Trainor, Dan Turetsky, An effective classification of Borel Wadge classes. J. Eur. Math. Soc. (2025), published online first
DOI 10.4171/JEMS/1655