Scale-free unique continuation estimates and applications to random Schr\"odinger operators

TL;DR

This paper establishes a scale-free unique continuation principle for Schr"odinger eigenfunctions, enabling new insights into eigenvalue perturbations and spectral properties of random Schr"odinger operators, with explicit parameter dependence.

Contribution

It introduces a scale-free unique continuation estimate for Schr"odinger eigenfunctions applicable to cubes of odd integer side length, with explicit constants and no dependence on the scale.

Findings

Derived Wegner estimates for Delone-Anderson models

Established lower bounds for spectral minimum shifts

Proved an uncertainty relation for spectral projectors

Abstract

We prove a unique continuation principle or uncertainty relation valid for Schr\"odinger operator eigenfunctions, or more generally solutions of a Schr\"odinger inequality, on cubes of side $L\in 2\NN+1$. It establishes an equi-distribution property of the eigenfunction over the box: the total $L^2$-mass in the box of side $L$ is estimated from above by a constant times the sum of the $L^2$-masses on small balls of a fixed radius $\delta>0$ evenly distributed throughout the box. The dependence of the constant on the various parameters entering the problem is given explicitly. Most importantly, there is no $L$-dependence. This result has important consequences for the perturbation theory of eigenvalues of Schr\"odinger operators, in particular random ones. For so-called Delone-Anderson models we deduce Wegner estimates, a lower bound for the shift of the spectral minimum, and an uncertainty relation for spectral projectors.