On the vortex motion in high temperature superconductors

We show that prominent features in voltage-current characteristics, recently measured in the mixed state of high-Tc superconductors and interpreted as evidence for an irreversibility line or a vortex-glass transition, may very well be explained with the simplest Kim-Anderson approach describing the vortex motion. In this case, the irreversibility line is not related to a transition in the system of vortices. Consulting numerous experimental reports on this subject we have not found a single example, which is in contradiction with this view.