The spectral gap and it's decidability

[#neutrino]

The article on undecidability of presence of spectral gap by describing its microscopic structure seems to contradict the fact that we can decide whether a CNT is metallic or semi -conducting by checking its diameter and its twist.

 

[mfb]

It does not. It applies to infinite systems only, and probably only to a few pathological cases.
We have a thread about the article already.