Tricritical behavior of the frustrated XY antiferromagnet
  Extensive histogram Monte-Carlo simulations of the XY antiferromagnet on a stacked triangular lattice reveal exponent estimates which strongly favor a scenario of mean-field tricritical behavior for the spin-order transition. The corresponding chiral-order transition occurs at the same temperature but appears to be decoupled from the spin-order. These results are relevant to a wide class of frustrated systems with planar-type order and serve to resolve a long-standing controversy regarding their criticality. 
M.L. Plumer, A. Mailhot, and A. Caill\'e (Centre de Recherche en   Physique du Solide et D\'epartement de Physique, Universi...