Isomorphism relations on computable structures
Ekaterina B. Fokina, Sy‐David Friedman, Valentina Harizanov, Julia F. Knight, Charles F. D. McCoy, Antonio Montalbán · Journal of Symbolic Logic · 2012
Abstract We study the complexity of the isomorphism relation on classes of computable structures. We use the notion of FF-reducibility introduced in [9] to show completeness of the isomorphism relation on many familiar classes in the context of all equivalence relations on hyperarithmetical subsets of ω.