title: Spectral properties of microwave graphs with local absorption.
abstract: The influence of absorption on the spectra of microwave graphs has been studied experimentally. The microwave networks were made up of coaxial cables and T junctions. First, absorption was introduced by attaching a 50Ω load to an additional vertex for graphs with and without time-reversal symmetry. The resulting level-spacing distributions were compared with a generalization of the Wigner surmise in the presence of open channels proposed recently by Poli et al. [Phys. Rev. Lett. 108, 174101 (2012)]. Good agreement was found using an effective coupling parameter. Second, absorption was introduced along one individual bond via a variable microwave attenuator, and the influence of absorption on the length spectrum was studied. The peak heights in the length spectra corresponding to orbits avoiding the absorber were found to be independent of the attenuation, whereas, the heights of the peaks belonging to orbits passing the absorber once or twice showed the expected decrease with increasing attenuation.
authors.affiliation: Fachbereich Physik der Philipps-Universität Marburg, D-35032 Marburg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Allgaier
authors.affiliation: Fachbereich Physik der Philipps-Universität Marburg, D-35032 Marburg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Gehler
authors.affiliation: Fachbereich Physik der Philipps-Universität Marburg, D-35032 Marburg, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Barkhofen
authors.affiliation: Fachbereich Physik der Philipps-Universität Marburg, D-35032 Marburg, Germany.
authors.forename: H-J
authors.initials: HJ
authors.lastname: Stöckmann
authors.affiliation: LPMC, CNRS UMR 7336, Université de Nice Sophia-Antipolis, F-06108 Nice, France and Fachbereich Physik der Philipps-Universität Marburg, D-35032 Marburg, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kuhl