Resistive transition of high-temperature superconductors

The model proposed recently by Yeshurun and Malozemoff to explain the ``irreversibility line'' in high-temperature superconductors is extended to account for the experimentally measured width and shape of the resistive transition in a magnetic field, without invoking material inhomogeneity. It is argued that high T_c and H_c2 are necessary, but not sufficient, conditions for such materials to show zero resistance at room temperature in substantial magnetic fields.