2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/164472When a macroscopic metallic wire is subject to tensile stress, it necks down smoothly as it elongates. We show that nanowires with radii comparable to the Fermi wavelength display remarkably different behavior. Using concepts from fluid dynamics, a PDE for nanowire shape evolution is derived from a semiclassical energy functional that includes electron-shell effects. A rich dynamics involving movement and interaction of kinks connecting locally stable radii is found, and a new class of universal equilibrium shapes is predicted.4 pages, 3 postscript figures. New result on universal equilibrium shapesMesoscale and Nanoscale PhysicsPattern Formation and SolitonsFluid Dynamicstext