  We report on our experimental evidence of a substantial geometrical
ingredient characterizing the problem of incipient dissipation in high-T_c
superconductors(HTS): high-resolution studies of differential
resistance-current characteristics in absence of magnetic field enabled us to
identify and quantify the fractal dissipative regime inside which the actual
current-carrying medium is an object of fractal geometry. The discovery of a
fractal regime proves the reality and consistency of critical-phenomena
scenario as a model for dissipation in inhomogeneous and disordered HTS, gives
the experimentally-based value of the relevant finite-size scaling exponent and
offers some interesting new guidelines to the problem of pairing mechanisms in
HTS.
