I'm confused how the paper's result (which you have posted) solves this question. I didn't read the paper, but the abstract only gave a looser bound that the sum of the first two eigenvalues is <= 2/sqrt(3) * n (and not just n).
Is this really solved?
I'm confused how the paper's result (which you have posted) solves this question. I didn't read the paper, but the abstract only gave a looser bound that the sum of the first two eigenvalues is <= 2/sqrt(3) * n (and not just n).