Noise exponent in superconducting-normal metal mixtures

The noise exponent ${\kappa }^{\prime }$ is calculated in a superconductor-normal-conductor network near the percolation threshold using the Midgal-Kadanoff bond-moving method. In two dimensions, ${\kappa }^{\prime }=1.339=\kappa$, where $\kappa$ is the noise exponent in a normal conductor-insulator network, consistent with duality arguments. In three dimensions, ${\kappa }^{\prime }=0.660\mathrm{}$, which lies between the exact upper and lower bounds $0.38\le {\kappa }^{\prime }\le 1.02$.