Nadirashvili' Conjecture for Elliptic PDEs and its Applications

TL;DR

This paper proves Nadirashvili's conjecture for harmonic functions, extends it to general elliptic PDEs, and explores various applications using nodal set bounds and elliptic estimates.

Contribution

The paper confirms Nadirashvili's conjecture for harmonic functions and general elliptic PDEs, providing new bounds and applications in the field.

Findings

Bounded nodal volume implies finite derivative sum bounds.

Extension of the conjecture to elliptic PDEs with smooth coefficients.

Applications in analysis and PDE theory.

Abstract

In this article, we investigate the conjecture posed by Nadirashvili in 1997. It states that if a harmonic function has bounded nodal volume in the unit ball, then the supermum over the half-ball can be bounded by a finite sum of derivatives at the center. The main tool in this paper is the lower bound of nodal sets, which is first proved by Alexander Logunov. Also we combine the propagation of smallness property and elliptic estimates to give a positive answer to this conjecture. In fact, we can extend this conjecture to general elliptic PDEs with smooth coefficients and also obtain a weak verison for less regular coefficients. Finally, we give several applications of this conjecture.