Yeah, my guess is that both are senile if they're putting this on the arxiv.
Second-order evidence: Old mathematicians (~80). Famous problem. Weird, imprecise writing style. No mention of the proof by mainstream mathematical news sources (breakthroughs are usually accompanied by excited blogging/tweeting). No acknowledgements directed at other mathematicians who have checked or commented on the proof.
[deleted argument here; replaced by more precise comment below]
My tone is harsh because I think the best thing to do is to quietly ignore it, similar to how the community treated Atiyah's claims of a RH proof at the end of his life.
Some counterpoints: 2 mathematicians greatly increases chances of senility. Blogs/twitter also correlate much stronger with author age than truth of statement.
>The argument looks like it's based on large n asymptotics, so even assuming everything works correctly the strongest statement they can hope to show is that the theorem is true for all n > n_0, where n_0 is some large constant. But there is no mention of this fact. The theorem is claimed for all n.
This is completely wrong. A proof for all n>n_0 is a proof for all n, since any counter-examples have to exist as subgraphs of arbitrarily large graphs.
I don't think asymptotic estimates of that form suffice to treat this problem. (Where else in combinatorics has an argument of this form succeeded? What intuitive reason is there to expect it to succeed here?)
Specifically I think section 4 is basically nonsense. (I see Sniffnoy has already pointed this out below.)
(Re: your comment, Theorem 7 is going to fail below the smallest counterexample, right? This is bad, imprecise writing - a red flag.)
> The argument looks like it's based on large n asymptotics, so even assuming everything works correctly the strongest statement they can hope to show is that the theorem is true for all n > n_0, where n_0 is some large constant. But there is no mention of this fact. The theorem is claimed for all n.
The point is that if there were a small graph that was a counter-example, then there would be large graph counter-examples (and the percentage of them would increase with graph size), so proving that the 4 color theorem is true for large graphs implies that it is true for all graph sizes.
> the argument looks like it's based on large n asymptotics, so even assuming everything works correctly the strongest statement they can hope to show is that the theorem is true for all n > n_0, where n_0 is some large constant. but there is no mention of this fact. the theorem is claimed for all n.
They're claiming:
> Theorem 7. If there is a map L which cannot be 4-coloured then only an exponentially small fraction of the maps with n edges can be 4-coloured.
It's not bizarre at all. The math community has unfortunately been down this road many times before. When an 80-year-old announces a 7 page proof of a famous problem, the smart money is on the proof being wrong. As the comments elsewhere on this story indicate, this heuristic turned out to be correct. The only new twist is that we have two 80-year-olds this time, not one.
To be clear, I don't like this state of affairs. As suggested above, the best course of action seems to be to ignore the posting.
>It's so inappropriate that in the field that's actually trained for this, they're disallowed by compact, even with extensive evidence.
The field trained for this is not refraining from this because it's hard to get right, but because it undermines the privacy promise they give their clients! not an argument applicable to people who do not have that professional reputation to uphold.
Of course you should speculate about mental health of people when it's relevant to the topic - it's a factor heavily shaping many people's behaviour!
Second-order evidence: Old mathematicians (~80). Famous problem. Weird, imprecise writing style. No mention of the proof by mainstream mathematical news sources (breakthroughs are usually accompanied by excited blogging/tweeting). No acknowledgements directed at other mathematicians who have checked or commented on the proof.
[deleted argument here; replaced by more precise comment below]
My tone is harsh because I think the best thing to do is to quietly ignore it, similar to how the community treated Atiyah's claims of a RH proof at the end of his life.