
Stability of a Szegő-type asymptotics
P. Müller, R. Schulte
We consider a multi-dimensional continuum Schrödinger operator H which is given by a perturbation of the negative Laplacian by a compactly supported bounded potential. We show that, for a fairly large class of test functions, the second-order Szegő-type asymptotics for the spatially truncated Fermi projection of H is independent of the potential and, thus, identical to the known asymptotics of the Laplacian.

Special issue on Mathematical Results in Quantum Mechanics
M. Christandl, H. Cornean, S. Fournais, P. Müller, J.Schach Møller (Editors)
Rev. Math. Phys. 33 (1), (2020).

Stability of the Enhanced Area Law of the Entanglement Entropy
P. Müller, R. Schulte
Ann. H. Poincaré 21, 3639 – 3658 (2020).
We consider a multi-dimensional continuum Schrödinger operator which is given by a perturbation of the negative Laplacian by a compactly supported potential. We establish both an upper bound and a lower bound on the bipartite entanglement entropy of the ground state of the corresponding quasi-free Fermi gas. The bounds prove that the scaling behaviour of the entanglement entropy remains a logarithmically enhanced area law as in the unperturbed case of the free Fermi gas. The central idea for the upper bound is to use a limiting absorption principle for such kinds of Schrödinger operators.