# On s-harmonic functions on cones

## TL;DR

This paper investigates the behavior of s-harmonic functions on cones as s approaches 1, revealing that convergence to harmonic functions depends on the cone's opening via an eigenvalue problem, with implications for free boundary problems.

## Contribution

It introduces an analysis of s-harmonic functions on cones as s approaches 1, linking convergence to an eigenvalue problem on the sphere, and explores implications for free boundary problems.

## Key findings

- Convergence of s-harmonic functions depends on the cone opening.
- Eigenvalue problem on the sphere determines the limit behavior.
- Results impact the study of free boundary problems and monotonicity formulas.

## Abstract

We deal with non negative functions satisfying \[ \left\{ \begin{array}{ll} (-\Delta)^s u_s=0 & \mathrm{in}\quad C, u_s=0 & \mathrm{in}\quad \mathbb{R}^n\setminus C, \end{array}\right. \] where $s\in(0,1)$ and $C$ is a given cone on $\mathbb R^n$ with vertex at zero. We consider the case when $s$ approaches $1$, wondering whether solutions of the problem do converge to harmonic functions in the same cone or not. Surprisingly, the answer will depend on the opening of the cone through an auxiliary eigenvalue problem on the upper half sphere. These conic functions are involved in the study of the nodal regions in the case of optimal partitions and other free boundary problems and play a crucial role in the extension of the Alt-Caffarelli-Friedman monotonicity formula to the case of fractional diffusions.