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A Hybrid Method for Inverse Obstacle Scattering Problems / Ein hybride Verfahren für inverse StreuproblemePicado de Carvalho Serranho, Pedro Miguel 02 March 2007 (has links)
No description available.
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On the Construction of Quantum Field Theories with Factorizing S-Matrices / Über die Konstruktion von quantenfeldtheoretischen Modellen mit faktorisierenden S-MatrizenLechner, Gandalf 24 May 2006 (has links)
No description available.
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Spectral theory of automorphism groups and particle structures in quantum field theory / Die Spektraltheorie von Automorphismengruppen und Teilchenstrukturen in der QuantenfeldtheorieDybalski, Wojciech Jan 15 December 2008 (has links)
No description available.
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Transport in nicht-hermiteschen niedrigdimensionalen Systemen / Transport in Non-Hermitian Low-Dimensional SystemsBendix, Oliver 20 September 2011 (has links)
No description available.
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Unitary aspects of Hermitian higher-order topological phasesFranca, Selma 01 March 2022 (has links)
Robust states exist at the interfaces between topologically trivial and nontrivial phases of matter. These boundary states are expression of the nontrivial bulk properties through a connection dubbed the bulk-boundary correspondence. Whether the bulk is topological or not is determined by the value of a topological invariant. This quantity is defined with respect to symmetries and dimensionality of the system, such that it takes only quantized values. For static topological phases that are realized in ground-states of isolated, time-independent systems, the topological invariant is related to the properties of the Hamiltonian operator. In contrast, Floquet topological phases that are realized in open systems with periodical pumping of energy are topologically characterized with a unitary Floquet operator i.e., the time-evolution operator over the entire period.
Topological phases of matter can be distinguished by the dimensionality of robust boundary states with respect to the protecting bulk. This dissertation concerns recently discovered higher-order topological phases where the difference between dimensionalities of bulk and boundary states is larger than one. Using analytical and numerical single-particle techniques, we focus on instances where static higher-order topology can be understood with insights from the mature field of Floquet topology. Namely, even though static systems do not admit a Floquet description, we find examples of higher-order systems to which certain unitary operators can be attributed. The understanding of topological characteristics of these systems is therefore conditioned by the knowledge on topological properties of unitary operators, among which the Floquet operator is well-known.
The first half of this thesis concerns toy models of static higher-order topological phases that are topologically characterized in terms of unitary operators. We find that a class of these systems called quadrupole topological insulators exhibit a wider range of topological phases than known previously. In the second half of this dissertation, we study reflection matrices of higher-order topological phases and show that they can exhibit the same topological features as Floquet systems. Our findings suggest a new route to experimental realizations of Floquet systems, the one that avoids noise-induced decoherence inevitable in many other experimental setups.
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Tailored disorder and anisotropic scattering in photonic nanostructuresVarytis, Paraschos 11 December 2019 (has links)
In dieser Arbeit untersuchen wir das optische Antwortverhalten von planaren Spektrometern basierend auf ungeordneten Streuzentren, dielektrischen Verbundnanopartikeln mit einer plasmonischer Ummantelung, sowie volldielektrischen magnetooptischen formveränderten Metaoberflächen. Dafür benutzen wir sowohl Mie und Mehrfach-Streutheorie als auch ein unstetiges Galerkin Zeitraumverfahren basierend auf finiten
Elementen zur numerischen Berechnung der elektromagnetischen Felder. Wir stellen
insbesondere eine theoretische Designstudie vor, um ungeordnete Spektrometer mit
hoher spektraler Auflösung zu erhalten. Darüber hinaus geben wir eine alternative
Strategie an, um durch Untersuchung der optischen Eigenschaften von Verbundnanopartikeln eine Erhöhung der bevorzugten Rückstreuung zu erreichen. Zum Schluss präsentieren wir eine Erhöhung der Faraday-Rotation bei gleichzeitig hoher Transmission von
volldielektrischen magnetooptischen Metaoberflächen, welche aus formangepassten Nanodisks bestehen. / In this thesis, we study the optical response of planar spectrometers based on disorder scatterers, composite dielectric nanoparticles with plasmonic shell, and all-dielectric
magneto-optical shape-modified metasurfaces. Therefore, we employ both Mie and multiple scattering theory as well as a discontinuous Galerkin time-domain method based on
finite elements for the numerical computation of the electromagnetic fields. Specifically,
we present a theoretical design study for obtaining random spectrometers with high
spectral resolution. Furthermore, we provide an alternative strategy to achieve preferentially high backscattering by studying the optical properties of composite nanoparticles.
Finally, we present enhanced Faraday rotation along with high transmittance in all-dielectric magneto-optical metasurfaces composed of shape-modified nanodisks.
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