Qizhen Shen | Searcharxiv

arXiv2026

A Quantitative Gidas--Ni--Nirenberg Theorem for the Fractional Laplacian

We establish a quantitative Gidas--Ni--Nirenberg theorem for the pure fractional Dirichlet problem \[ (-Δ)^s u=k(x)g(u)\quad\text{in }B_1, \qquad u=0\quad\text{in }\mathbb R^n\setminus B_1, \qquad 0<s<1. \] For positive bounded solutions under a two-sided $L^\infty$ normalization, we prove \[ \mathcal D(u)\le C\,\mathcal D(k)^γ,\qquad 0<γ<1, \] where $\mathcal D$ measures spherical oscillation and outward radial increase. To the best of our knowledge, this provides the first quantitative Gidas--Ni--Nirenberg estimate for the pure fractional Dirichlet problem. The key new ingredient is a shift-uniform, weak Harnack inequality for shifted antisymmetric supersolutions, which overcomes the exterior-tail obstruction in the quantitative moving-plane argument. This mechanism extends to nonseparable nonlinearities.

math.AP↗

arXiv2026

Pointwise regularity of solutions for fully fractional parabolic equations

This paper investigates the higher pointwise regularity of nonnegative classical solutions for fully fractional parabolic equations $(\partial_t -Δ)^{s} u = f,$ where $s\in(0,1)$. We establish $C^{k+α+2s}$ or $C^{k+α+2s,\ln} (k\geq 0,α\in[0,1))$ pointwise regularity according to $α+2s\notin \mathbb{Z}$ or $α+2s\in \mathbb{Z}$, which imply the classical local regularity directly. We provide a simplified and unified proof by introducing novel equivalent definitions for pointwise function spaces. Moreover, the equivalent integral representation and directional average for fractional heat kernel play an important role in our discussion.

math.AP↗