Quantum phase transition in disorder antiferromagnet with hidden degrees of freedom

The problem of existence of long-range order at or close to the critical point of the quantum phase transition in the disordered antiferromagnet with hidden degrees of freedom is discussed. The influence of the constraint upon hidden degrees of freedom within the renormalization group theory is considered. 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.