title: Comment on "Six-state clock model on the square lattice: Fisher zero approach with Wang-Landau sampling".
abstract: Hwang in [Phys. Rev. E 80, 042103 (2009)] suggested that the two transitions of the six-state clock model on the square lattice are not of the Kosterlitz-Thouless type. Here we show from simulations that at the upper transition, the helicity modulus does make a discontinuous jump to zero. This gives strong evidence for a Kosterlitz-Thouless transition.
authors.affiliation: Department of Physics, Umeå University, 901 87 Umeå, Sweden.
authors.forename: Seung Ki
authors.initials: SK
authors.lastname: Baek
authors.forename: Petter
authors.initials: P
authors.lastname: Minnhagen
authors.forename: Beom Jun
authors.initials: BJ
authors.lastname: Kim