# Analysis Seminar: Dirk Hundertmark (Karlsruhe) "Quantum Systems at the Brink: Helium"

## Location:

Title: Quantum Systems at the Brink: Helium

Abstract: Perturbation theoryworks well for the the discrete spectrum below the essential spectrum. Whathappens if a parameter of a quantum system is tuned in such a way that abound state energy (e.g. the ground state energy) hits the bottom of theessential spectrum? Does the eigenvalue survive, i.e., the correspondingeigenfunction stays $L^2$, or does it dissolve into the continuumenergies?

It turns out the