Schrödinger operators on graphs and geometry. II: Spectral estimates for \(L_1\)-potentials and an Ambartsumian theorem
The boundary value problem \(L(q)\) is considered for the Sturm-Liouville equation \[ -y''+q(x)y=\lambda y \] on a compact graph under the so-called standard boundary conditions. The main result is an estimate of the difference between eigenvalues of two boundary value problems \(L(q)\) and \(L(0)\). For Part I, see [the second author, J. Funct. Anal. 254, No. 4, 934--953 (2008; Zbl 1140.81387)].
scientific article; zbMATH DE number 6909750
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