This paper studies when an arithmetical equivalence relation E can be realized as the connectedness relation of a graph G which is simpler to define than E. Several examples of such equivalence relations are established. In particular, it is proved that the ⁰₃ relation of computable isomorphism of structures on in a computable first-order language is ⁰₂-graphable, i. e. , is the connectedness relation of a ⁰₂ graph. Graphings of Friedman-Stanley jumps are studied, including an arithmetical construction of a graphing of the Friedman-Stanley jump of E from a graphing of E.
Tyler Arant (Tue,) studied this question.
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