> Does that imply that it could be possible to construct a system which gives uncomputable results? They produce a family of systems for which it is not possib

> Does that imply that it could be possible to construct a system which gives uncomputable results? They produce a family of systems for which it is not possible to construct an algorithm that can yield a certain property (being gapped) of each system. > Does it assume an infinite plane or something? (Assume might be the wrong word) Yes. The system is infinite. (Or, take a limit as the system size grows to infinity.)