Diluted Networks of Nonlinear Resistors and Fractal Dimensions of Percolation Clusters

TL;DR

This paper develops a renormalized field theory for nonlinear resistor networks to compute fractal dimensions of percolation clusters, confirming and extending previous theoretical results.

Contribution

It introduces a detailed field-theoretic approach to analyze nonlinear resistor networks and calculates several fractal dimensions, verifying and extending prior theoretical findings.

Findings

d_red = 1/nu at order O(ε^4)

d_min matches previous calculations up to second order in ε

D_B agrees with two-loop calculations by Harris and Lubensky

Abstract

We study random networks of nonlinear resistors, which obey a generalized Ohm's law, $V\sim I^r$. Our renormalized field theory, which thrives on an interpretation of the involved Feynman Diagrams as being resistor networks themselves, is presented in detail. By considering distinct values of the nonlinearity r, we calculate several fractal dimensions characterizing percolation clusters. For the dimension associated with the red bonds we show that $d_{\scriptsize red} = 1/\nu$ at least to order ${\sl O} (\epsilon^4)$, with $\nu$ being the correlation length exponent, and $\epsilon = 6-d$, where d denotes the spatial dimension. This result agrees with a rigorous one by Coniglio. Our result for the chemical distance, $d_{\scriptsize min} = 2 - \epsilon /6 - [ 937/588 + 45/49 (\ln 2 -9/10 \ln 3)] (\epsilon /6)^2 + {\sl O} (\epsilon^3)$ verifies a previous calculation by one of us. For the backbone dimension we find $D_B = 2 + \epsilon /21 - 172 \epsilon^2 /9261 + 2 (- 74639 + 22680 \zeta (3))\epsilon^3 /4084101 + {\sl O} (\epsilon^4)$, where $\zeta (3) = 1.202057...$, in agreement to second order in $\epsilon$ with a two-loop calculation by Harris and Lubensky.