Remeslennikov’s conjecture on profinite rigidity of free groups
Prove that if a residually finite group $G$ has the same finite quotients (equivalently, the same profinite completion) as a free group of rank at least 2, then $G$ is free.
References
A major open problem in group theory is Remeslennikov's conjecture: if $G$ is a residually finite group with the same finite quotients as a free group, is $G$ necessarily free?
— The theory of one-relator groups: history and recent progress
(2501.18306 - Linton et al., 30 Jan 2025) in Subsection 7.6 (Residual and virtual properties; profinite completions)