Resistivity of high-Tcsuperconductors in a vortex-liquid state

The theory of pinning of a vortex liquid by weak disorder is developed. Two different vortex-liquid dissipative regimes are shown to exist: the flux flow above some crossover temperature ${\mathit{T}}_{\mathit{k}}$, where the vortex liquid is unpinned, and the thermally assisted flux flow below ${\mathit{T}}_{\mathit{k}}$. The activation barriers in the latter regime are those associated with the plastic motion of the vortices in the liquid.