Electrical networks on $n$-simplex fractals

The decimation map $\mathcal{D}$ for a network of admittances on an $n$-simplex lattice fractal is studied. The asymptotic behaviour of $\mathcal{D}$ for large-size fractals is examined. It is found that in the vicinity of the isotropic point the eigenspaces of the linearized map are always three for $n\ge 4$; they are given a characterization in terms of graph theory. A new anisotropy exponent, related to the third eigenspace, is found, with a value crossing over from $\ln [(n+2)\mathrm{/}3]\mathrm{/}\ln 2$ to $\ln [(n+2{)}^3\mathrm{/}n(n+1{)}^2]\mathrm{/}\ln 2$.