# Mathematics Colloquia and Seminars

### A simple variational bound for eigenvalues of discrete Schroedinger operators with potentials of arbitrary sign

Mathematical Physics & Probability

 Speaker: D. Hundertmark, Caltech Location: 693 Kerr Start time: Tue, Jun 4 2002, 3:10PM

Variational bounds have been one of the major tools in the study of discrete eigenvalues of Schr\"odinger operators. However, they are usually not applicable if the potential is allowed to change signs. We give a simple variational bound for eigenvalues of discrete Schr\"odinger operators which does not require the potential to be of fixed sign. A consequence of this bound is a simple proof of the fact that if the spectrum of a discrete Schr\"odinger operator on \$\mathbb{Z}\$ is [-2,2], then the potential must vanish identically. Also, certain eigenvalue moments must blow up for slowly decaying potentials, even if they are highly oscillating. Most results extend to higher dimensions.