Comment on "Quantum phase transition in the four-spin exchange antiferromagnet" by V. N. Kotov, D.-X. Yao, A. H. Castro-Neto, and D. K. Campbell

L. Isaev, G. Ortiz, J. Dukelsky

In a recent paper [Phys. Rev. {\bf B80}, 174403 (2009)] Kotov {\it et al.} studied the paramagnetic-to-antiferromagnetic transition in the $J$-$Q$ model. Their findings were claime…