Spin stiffness of canted antiferromagnets.

We use a nonlinear O(3)⊗O(2)/O(2) sigma model to describe the long-distance properties of two-dimensional classical Heisenberg canted antiferromagnets. The two-loop correlation length as well as the spin stiffness tensor are obtained by means of a renormalization-group calculation. Our results are applied to the triangular antiferromagnet. A discussion of possible comparison with Monte Carlo simulations is finally made