Proceedings of the London Mathematical Society Advance Access published online on May 1, 2008
Proceedings of the London Mathematical Society, doi:10.1112/plms/pdn020
© 2008 London Mathematical Society
Spectra of graph neighborhoods and scattering
Institut für Mathematik
Carl von Ossietzky Universität Oldenburg
D-26111 Oldenburg
Germany
Received 20 November 2007.
Let (G
)
>0 be a family of
-thin Riemannian manifolds modeled on a finite metric graph G, for example, the
-neighborhood of an embedding of G in some Euclidean space with straight edges. We study the asymptotic behavior of the spectrum of the Laplace–Beltrami operator on G
, as 
0, for various boundary conditions. We obtain complete asymptotic expansions for the kth eigenvalue and the eigenfunctions, uniformly for k
C
–1, in terms of scattering data on a non-compact limit space. We then use this to determine the quantum graph which is to be regarded as the limit object, in a spectral sense, of the family (G
). Our method is a direct construction of approximate eigenfunctions from the scattering and graph data, and the use of a priori estimates to show that all eigenfunctions are obtained in this way.
2000 Mathematics Subject Classification 58J50 35P99 (Primary) 47A55 81Q10 (Secondary).