Static and dynamic vortex transitions in clean YBa{sub 2}Cu{sub 3}O{sub 7}

The evidence establishing first order melting of the vortex lattice in clean YBa{sub 2}Cu{sub 3}O{sub 7} is reviewed. Dynamic transitions in the moving vortex system are demonstrated experimentally through resistivity and magnetization measurements. In general there is a strong interplay between dynamic transitions and equilibrium phase transitions, because the character of the motion is determined in part by the same thermal fluctuation and interaction energies among vortices and pin sites which control the equilibrium phases