STABILITY OF VORTEX LINES IN LIQUID HE-3-HE-4 MIXTURES AT ZERO-TEMPERATURE

At low temperatures and He-3 concentrations below similar to 6.6%, the re is experimental evidence about the existence in liquid helium mixtu res of stable vortices with He-3-rich cores. When the system is either supersaturated or submitted to a tensile strength, vortices lose stab ility becoming metastable and eventually completely unstable, so that their cores freely expand. Within a density functional approach, we ha ve determined the pressure-He-3 concentration curve along which this i nstability appears at zero temperature.