Chiral transitions in three-dimensional magnets and higher order   \epsilon-expansion
  The critical behaviour of helimagnets and stacked triangular antiferromagnets is analyzed in (4 - \epsilon) dimensions within three-loop approximation. Numerical estimates for marginal values of the order parameter dimensionality N obtained by resummation of corresponding \epsilon-expansions rule out the possibility of continuous chiral transitions in magnets with Heisenberg or planar spins. 
S. A. Antonenko, A. I. Sokolov, K. B. Varnashev (Saint Petersburg   Electrotechnical University, St.Petersburg, Russia)