  The planar Heisenberg system with antiferroquadrupolar exchange on 3D stacked
triangular lattice is shown to belong to the new "chiral" universality class,
predicted for chiral antiferromagnets. The present system, however, displays no
such chirality, which, according to the currently widely accepted concept, is
supposed to be a key ingredient for the new critical behavior. Our claim that
the new universality class should not be limited only to the chiral
antiferromagnets is based on a simple mapping between the chiral
antiferromagnetic and antiferroquadrupolar systems and supported by actual
calculations of the transition temperatures and critical indices from
finite-size scaling analysis of data issued from Histogram Monte Carlo
simulations. In order to demonstrate the existence of two different
universality classes in the behavior of quadrupolar systems, the finite-size
scaling is also performed for the system with ferroquadrupolar exchange, which,
in contrast to the antiferroquadrupolar exchange system case, produced standard
critical behavior, as could also be anticipated from the mapping.
