Vortex dynamics in strong pinning theory
Magnetic field penetrates into a superconducting material via topological defect lines, vortices. Electric and magnetic properties of superconductors in a so called mixed state is determined by properties of ``Vortex matter". This vortex matter is pushed by the transport current and its motion induces an electric field and thus dissipation. It is pinning of vortices by material defects that recovers most valuable property of dissipation free current in superconductors. I review recent applications of strong pinning theory for vortex dynamics. We derive linear current voltage characteristic above depinning which resembles the Coulomb’s law of dry friction. We consider effect of thermal fluctuations (flux creep) and ac response in the mixed state.