We prove that the Hausdorff dimension of the spectrum of a discrete Schrödinger operator with Sturmian potential of bounded type tends to one as coupling tends to zero. The proof is based on the trace map formalism.
A Hamiltonian-Krein (instability) index theory for KdV-like eigenvalue problems
Hamiltonian-Krein(不稳定性)指标涉及确定具有正实部的Hamiltonian本征值问题$ J L u=λu$的特征值的数目,其中$J$是反对称的,并且$L$是自伴的。如果$J$有一个有界的逆的指数是良好建立的,它是由运营商$L$限制到一些有限余维子空间上的负特征值的数量。有一类重要的问题--即KdV型问题--对于这些问题,$J$没有有界逆。本文克服了这一困难,推导出了KdV型本征值问题的指标。利用该指数讨论了KdV类问题和BBM类问题的同宿行波的谱稳定性。
We study the spectrum of the spin-boson Hamiltonian with two bosons for arbitrary coupling $α>0$ in the case when the dispersion relation of the free field is a bounded function. We derive an explicit description of the essential spectrum which consists of the so-called two and three-particle branches that can be separated by a gap if the coupling is sufficiently large. It turns out, that depending on the location of the coupling constant and the energy level of the atom (with respect to certain constants depending on the maximal and the minimal values of the boson energy) as well as the valid…
We prove the limiting absorption principle and discuss the continuity properties of the boundary values of the resolvent for a class of form bounded perturbations of the Euclidean Laplacian $Δ$ that covers both short and long range potentials with an essentially optimal behaviour at infinity.