When he introduced surjunctive groups in 1973, Gottschalk observed that there were no known examples of non-surjunctive groups; as of 2014, it is still unknown whether every group is surjunctive.
When he introduced surjunctive groups in 1973, Gottschalk observed that there were no known examples of non-surjunctive groups; as of 2014, it is still unknown. Every group is surjunctive.