TESTING SINGULARITIES IN THE COMPLEX-PLANE - SUGGESTIONS FOR DENDRITIC-GROWTH EXPERIMENTS

The usual theories of selection in dendritic growth involve an analytical extension in the complex plane and a search of singularities for the profile function. We show here that the complex plane is in fact the liquid phase and that the zone of singularity lies on the growth axis. We find a selection mechanism, by using localized perturbations, for the dendritic growth even when the surface tension is isotropic. We show that it is possible to act on the complex plane and to modify at distances the growth rate and the shape of the solidification front. Moreover, we stress here the influence of localized perturbations on the measurement of the constant of stability sigma* of the needle crystal.