document.write("« The $\Sigma_2$ theory of $\mathscr{D}_h(\leq_h \mathcal{O})$ as an uppersemilattice with least and greatest element is decidable. (arXiv:1704.06347v1 [math.LO])");document.write(" | ");document.write("The Best of the Physics arXiv (week ending April 22, 2017) »");