Theory of collective flux creep

The nature of flux-creep phenomena in the case of collective pinning by weak disorder is discussed. The Anderson concept of flux bundle is explored and developed. The dependence of the bundle activation barrier, U, on current j is studied and is shown to be of power-law type: U(j)\ensuremath{\propto}${\mathrm{j}}^{\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\alpha}}}$. The values of exponent \ensuremath{\alpha} for the different regimes of collective creep are found.