From the 1 of 5 linked papers with an AI index.
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The epimorphism relation among countable groups is a complete analytic quasi-order
Su Gao, Feng Li, André Nies +1
We prove that the epimorphism relation is a complete analytic quasi-order on the space of countable groups. In the process, we obtain the result of independent interest that the ep…
Procountable groups are not classifiable by countable structures
Su Gao, André Nies, Gianluca Paolini
We prove that topological isomorphism on procountable groups is not classifiable by countable structures, in the sense of descriptive set theory. In fact, the equivalence relation…
Extremely amenable automorphism groups of countable structures
Mahmood Etedadialiabadi, Su Gao, Feng Li +1
In this paper we address the question: How many pairwise non-isomorphic extremely amenable groups are there which are separable metrizable or even Polish? We show that there are co…
On the Isomorphism Relation for Omnigenous Locally Finite Groups
Su Gao, Feng Li
The concept of an omnigenous locally finite group was introduced in [2] as a generalization of Hall's universal countable locally finite group. In this paper we show that the class…