Analysis of non-linear fractal functions on PCF self-similar sets
Aaryan Dharmesh Shah, Sangita Jha, Anarul Islam Mondal
TL;DR
This work develops a general nonlinear fractal interpolation framework on post-critically finite (PCF) self-similar sets using Edelstein contractions and nonconstant harmonic functions. It proves the existence and uniqueness of a graph-finite fractal interpolation function $f^*$ whose graph is the invariant set of a nonlinear IFS on $\mathcal{K}\times\mathcal{J}$ and satisfies $f^*(l_n(x)) = s_n(f^*(x)) + h_n(x)$ with prescribed data on $V_1$. The authors derive explicit box-dimension bounds for the graphs on the Sierpinski gasket and von-Koch curve, supported by examples, and analyze energy and normal derivatives, establishing finite-energy criteria in terms of $\Psi = \sum (L(s_n))^2$. By extending FIF theory beyond Lipschitz mappings, the paper provides a robust framework for nonlinear FIFs on a broad class of PCF fractals and clarifies their geometric and analytic properties.
Abstract
This article deals with (1) the construction of a general non-linear fractal interpolation function on PCF self-similar sets, (2) the energy and normal derivatives of uniform non-linear fractal functions, (3) estimation of the bound of box dimension of the proposed fractal functions on the Sierpinski gasket and the von-Koch curve. Here, we present a more general framework to construct the attractor and the functions on the PCF self-similar sets using the Edelstein contraction, which broadens the class of functions. En route, we calculate the upper and lower box dimensions of the graph of non-linear interpolant. Finally, we provide several graphical and numerical examples for illustration of the construction and estimate the dimensions for different data sets.
