In the present paper we are discussing the influence of the fractal distribution of defects on the critical behavior of the system. We consider a case when the equation of motion for the order parameter contains influences of defects of random field and random temperature types at the same time and we show that it can lead to a change of distribution function from Gibbs distribution to Tsallis distribution or more general statistics of q-type. We are able to extend the Landau-Khalatnikov equation for the order parameter and represent it in the form of a differential equation of the fractional order. We deduce and we solve the corresponding renormalization group equation with the nonlinear dispersion law and we calculate the critical indices of the system.
The critical behavior of the classical Ising model on a three-dimensional fractal lattice with Hausdorff dimension
dH=ln32/ln4=2.5 is investigated using the higher-order tensor renormalization group (HOTRG) method. We determine the critical temperature
Tc≈2.65231 and the critical exponents for magnetization
β≈0.059 and field response
δ≈35. Unlike a previously studied 2D fractal with
dH≈1.792, the specific heat for this 3D fractal exhibits a divergent singularity at
Tc. The results are compared with those for regular lattices and other fractal structures to elucidate the role of dimensionality in critical phenomena.