Hydrodynamic and Dynamical Phi^4 Limits of Ising-Kac Models with Diffusion-Based Interactions on the Sierpiński Gasket

Abstract

We introduce a general form of Ising--Kac interactions through heat-kernel averaging, with the heat-time parameter replacing the role of the interaction range. From the viewpoint of Dirichlet forms theory, this construction provides an intrinsic analogue of the mesoscopic averaging in classical Kac models when translation invariance is unavailable. We then investigate limits of this model on graph approximations of the Sierpiński gasket. For the associated Glauber dynamics, we establish a hierarchy of scaling limits for the magnetization field. First, at fixed interaction heat time and inverse temperature, we derive a nonlocal hydrodynamic equation on the continuum gasket. Second, as the heat time vanishes and the inverse temperature approaches its mean-field critical value, suitably rescaled hydrodynamic solutions converge to the solution of the deterministic Allen--Cahn equation. Finally, under a joint scaling of graph refinement, interaction heat time, and inverse temperature near criticality, we prove convergence of critical magnetization fluctuations to the solution of the dynamical $Φ^4$ equation. These results provide a concrete realization of the Ising-$Φ^4$ correspondence in a geometric setting with non-integer spectral dimension.