UNILATERAL RIGIDITY FROM INFINITY FOR NONLINEAR ALFVEN WAVES IN IDEAL MAGNETOHYDRODYNAMICS

In this paper we develop the rigidity from infinity theory of Alfven waves in strong constant magnetic backgrounds. Our previous bilateral rigidity for two separate families of Alfven waves is now strengthened to the unilateral rigidity. It is proved in the whole spacetime that if the scattering field of Alfven wave in any family vanishes at infinity, then the Alfven wave in this family vanishes identically, and moreover the fluid velocity is equivalent in size to and collinear to the perturbation of magentic field.