Influence of rare regions on quantum phase transition in   antiferromagnets with hidden degrees of freedom
  The effects of rare regions on the critical properties of quantum antiferromagnets with hidden degrees of freedom within the renormalization group is discussed. It is shown that for ``constrained'' systems the stability range on the phase diagram remains the same as in the mean-field theory while for ``unconstrained'' systems the stability range is effectively decreased. 
Y. N. Skryabin, A. V. Chukin and A. V. Shchanov