@phdthesis{8425, abstract = {{This thesis studies three topics in quantum computation and information: The approximability of quantum problems, quantum proof systems, and non-classical correlations in quantum systems. In the first area, we demonstrate a polynomial-time (classical) approximation algorithm for dense instances of the canonical QMA-complete quantum constraint satisfaction problem, the local Hamiltonian problem. In the opposite direction, we next introduce a quantum generalization of the polynomial-time hierarchy, and define problems which we prove are not only complete for the second level of this hierarchy, but are in fact hard to approximate. In the second area, we study variants of the interesting and stubbornly open question of whether a quantum proof system with multiple unentangled quantum provers is equal in expressive power to a proof system with a single quantum prover. Our results concern classes such as BellQMA(poly), and include a novel proof of perfect parallel repetition for SepQMA(m) based on cone programming duality. In the third area, we study non-classical quantum correlations beyond entanglement, often dubbed "non-classicality". Among our results are two novel schemes for quantifying non-classicality: The first proposes the new paradigm of exploiting local unitary operations to study non-classical correlations, and the second introduces a protocol through which non-classical correlations in a starting system can be "activated" into distillable entanglement with an ancilla system. An introduction to all required linear algebra and quantum mechanics is included.}}, author = {{Gharibian, Sevag}}, pages = {{240}}, title = {{{Approximation, Proof Systems, and Correlations in a Quantum World}}}, year = {{2013}}, } @article{8173, abstract = {{We study three variants of multi-prover quantum Merlin-Arthur proof systems. We first show that the class of problems that can be efficiently verified using polynomially many quantum proofs, each of logarithmic-size, is exactly MQA (also known as QCMA), the class of problems which can be efficiently verified via a classical proof and a quantum verifier. We then study the class BellQMA(poly), characterized by a verifier who first applies unentangled, nonadaptive measurements to each of the polynomially many proofs, followed by an arbitrary but efficient quantum verification circuit on the resulting measurement outcomes. We show that if the number of outcomes per nonadaptive measurement is a polynomially-bounded function, then the expressive power of the proof system is exactly QMA. Finally, we study a class equivalent to QMA(m), denoted SepQMA(m), where the verifier's measurement operator corresponding to outcome "accept" is a fully separable operator across the m quantum proofs. Using cone programming duality, we give an alternate proof of a result of Harrow and Montanaro [FOCS, pp. 633--642 (2010)] that shows a perfect parallel repetition theorem for SepQMA(m) for any m.}}, author = {{Gharibian, Sevag and Sikora, Jamie and Upadhyay, Sarvagya}}, journal = {{Quantum Information & Computation}}, number = {{1-2}}, pages = {{135--157}}, title = {{{QMA variants with polynomially many provers}}}, volume = {{13}}, year = {{2013}}, } @article{41591, author = {{Fuchs, Christian}}, journal = {{The Political Economy of Communication}}, number = {{2}}, pages = {{3--27}}, title = {{{Theorising and Analysing Digital Labour: From Global Value Chains to Modes of Production}}}, volume = {{1}}, year = {{2013}}, } @article{41597, author = {{Fuchs, Christian and Sandoval, Marisol}}, journal = {{tripleC: Communication, Capitalism & Critique}}, number = {{2}}, pages = {{428--443}}, title = {{{The Diamond Model of Open Access Publishing: Why Policy Makers, Scholars, Universities, Libraries, Labour Unions and the Publishing World Need to Take Non-Commercial, Non-Profit Open Access Serious}}}, doi = {{https://doi.org/10.31269/triplec.v11i2.502}}, volume = {{11}}, year = {{2013}}, } @article{41600, author = {{Fuchs, Christian and Sevignani, Sebastian}}, journal = {{tripleC}}, number = {{2}}, pages = {{237--293}}, title = {{{What Is Digital Labour? What Is Digital Work? What’s Their Difference? And Why Do These Questions Matter for Understanding Social Media?}}}, doi = {{https://doi.org/10.31269/triplec.v11i2.461}}, volume = {{11}}, year = {{2013}}, } @article{41596, author = {{Fuchs, Christian and Pieter, Verdegem}}, journal = {{Nordicom Review}}, number = {{2}}, pages = {{3--18}}, title = {{{Towards a Participatory, Co-operative and Sustainable Information Society? A Critical Analysis of Swedish ICT Policy Discourses}}}, volume = {{34}}, year = {{2013}}, } @article{41595, author = {{Fuchs, Christian}}, journal = {{Interface: A Journal for and about Social Movements}}, number = {{2}}, pages = {{345--376}}, title = {{{The Anonymous Movement in the Context of Liberalism and Socialism}}}, volume = {{5}}, year = {{2013}}, } @article{41598, author = {{Fuchs, Christian and Dyer-Witheford, Nick}}, journal = {{New Media & Society}}, number = {{5}}, pages = {{782--796}}, title = {{{Karl Marx @ Internet Studies}}}, doi = {{https://doi.org/10.1177/1461444812462854}}, volume = {{15}}, year = {{2013}}, } @article{42601, author = {{Fuchs, Christian}}, journal = {{tripleC}}, number = {{2}}, pages = {{294--309}}, title = {{{Why and How to Read Marx’s “Capital”? Reflections on Johan Fornäs’ book “Capitalism. A Companion to Marx’s Economy Critique“}}}, doi = {{https://doi.org/10.31269/triplec.v11i2.488}}, volume = {{11}}, year = {{2013}}, } @inbook{42925, author = {{Matzner, Tobias}}, booktitle = {{From the ALWS archives: A selection of papers from the International Wittgenstein Symposia in Kirchberg am Wechsel. Republication by the Wittgenstein Archives at the University of Bergen}}, title = {{{Morals in the world-picture}}}, year = {{2013}}, } @article{28146, author = {{Matzner, Tobias}}, issn = {{0951-5666}}, journal = {{AI & SOCIETY}}, number = {{1}}, pages = {{95--102}}, title = {{{The model gap: cognitive systems in security applications and their ethical implications}}}, doi = {{https://doi.org/10.1007/s00146-013-0525-4}}, volume = {{31}}, year = {{2013}}, } @article{43257, abstract = {{We demonstrate that trapping of dispersive waves between two optical solitons takes place when resonant scattering of the waves on the solitons leads to nearly perfect reflections. The momentum transfer from the radiation to solitons results in their mutual attraction and a subsequent collision. The spectrum of the trapped radiation can either expand or shrink in the course of the propagation, which is controlled by arranging either collision or separation of the solitons.}}, author = {{Yulin, A. V. and Driben, R. and Malomed, B.A. and Skryabin, D.V.}}, journal = {{Optics Express}}, number = {{12}}, title = {{{Soliton interaction mediated by cascaded four wave mixing with dispersive waves}}}, doi = {{10.1364/OE.21.014481}}, volume = {{21}}, year = {{2013}}, } @phdthesis{64748, author = {{Alzaareer, Hamza}}, title = {{{Lie groups of mappings on non-compact spaces and manifolds}}}, year = {{2013}}, } @phdthesis{64750, author = {{Schmeding, Alexander}}, title = {{{The diffeomorphism group of a non-compact orbifold}}}, year = {{2013}}, } @article{58526, author = {{Masri, Leila and Schulte, Rebecca D. and Timmermeyer, Nadine and Thanisch, Stefanie and Crummenerl, Lena Luise and Jansen, Gunther and Michiels, Nico K. and Schulenburg, Hinrich}}, journal = {{Ecology Letters}}, keywords = {{Bacillus thuringiensis, Bateman’s principle, Caenorhabditis elegans, ecological immunology, host–parasite coevolu- tion, Red Queen hypothesis, sexual selection}}, number = {{16}}, pages = {{461--468}}, title = {{{Sex differences in host defence interfere with parasite- mediated selection for outcrossing during host–parasite coevolution}}}, doi = {{10.1111/ele.12068}}, year = {{2013}}, } @article{13525, abstract = {{The frequency-dependent dielectric function and the second-order polarizability tensor of ferroelectric LiNbO3 are calculated from first principles. The calculations are based on the electronic structure obtained from density-functional theory. The subsequent application of the GW approximation to account for quasiparticle effects and the solution of the Bethe-Salpeter equation for the stoichiometric material yield a dielectric function that slightly overestimates the absorption onset and the oscillator strength in comparison with experimental measurements. Calculations at the level of the independent-particle approximation indicate that these deficiencies are, at least, partially related to the neglect of intrinsic defects typical for the congruent material. The second-order polarizability calculated within the independent-particle approximation predicts strong nonlinear coefficients for photon energies above 1.5 eV. The comparison with measured data suggests that the inclusion of self-energy effects in the nonlinear optical response leads to a better agreement with experiments. The intrinsic defects of congruent samples reduce the optical nonlinearities, in particular, for the 21 and 31 tensor components, further improving the agreement between experiments and theory.}}, author = {{Riefer, Arthur and Sanna, Simone and Schindlmayr, Arno and Schmidt, Wolf Gero}}, issn = {{1550-235X}}, journal = {{Physical Review B}}, number = {{19}}, publisher = {{American Physical Society}}, title = {{{Optical response of stoichiometric and congruent lithium niobate from first-principles calculations}}}, doi = {{10.1103/PhysRevB.87.195208}}, volume = {{87}}, year = {{2013}}, } @article{18476, abstract = {{We investigate the band dispersion and relevant electronic properties of rubrene single crystals within the GW approximation. Due to the self-energy correction, the dispersion of the highest occupied molecular orbital (HOMO) band increases by 0.10 eV compared to the dispersion of the Kohn-Sham eigenvalues within the generalized gradient approximation, and the effective hole mass consequently decreases. The resulting value of 0.90 times the electron rest mass along the Γ-Y direction in the Brillouin zone is closer to experimental measurements than that obtained from density-functional theory. The enhanced bandwidth is explained in terms of the intermolecular hybridization of the HOMO(Y) wave function along the stacking direction of the molecules. Overall, our results support the bandlike interpretation of charge-carrier transport in rubrene.}}, author = {{Yanagisawa, Susumu and Morikawa, Yoshitada and Schindlmayr, Arno}}, issn = {{1550-235X}}, journal = {{Physical Review B}}, number = {{11}}, publisher = {{American Physical Society}}, title = {{{HOMO band dispersion of crystalline rubrene: Effects of self-energy corrections within the GW approximation}}}, doi = {{10.1103/PhysRevB.88.115438}}, volume = {{88}}, year = {{2013}}, } @article{18479, abstract = {{The GW approximation for the electronic self-energy is an important tool for the quantitative prediction of excited states in solids, but its mathematical exploration is hampered by the fact that it must, in general, be evaluated numerically even for very simple systems. In this paper I describe a nontrivial model consisting of two electrons on the surface of a sphere, interacting with the normal long-range Coulomb potential, and show that the GW self-energy, in the absence of self-consistency, can in fact be derived completely analytically in this case. The resulting expression is subsequently used to analyze the convergence of the energy gap between the highest occupied and the lowest unoccupied quasiparticle orbital with respect to the total number of states included in the spectral summations. The asymptotic formula for the truncation error obtained in this way, whose dominant contribution is proportional to the cutoff energy to the power −3/2, may be adapted to extrapolate energy gaps in other systems.}}, author = {{Schindlmayr, Arno}}, issn = {{1550-235X}}, journal = {{Physical Review B}}, number = {{7}}, publisher = {{American Physical Society}}, title = {{{Analytic evaluation of the electronic self-energy in the GW approximation for two electrons on a sphere}}}, doi = {{10.1103/PhysRevB.87.075104}}, volume = {{87}}, year = {{2013}}, } @article{30766, abstract = {{Modelle Allgemeiner Didaktik sind in der Regel weder empirisch fundiert noch ist ihr Verhältnis zum realen Planungshandeln von Lehrerinnen und Lehrern geklärt. Theoretische Basis für empirische Studien zur Unterrichtsplanung sind selten allgemeindidaktische Modelle, sondern eher psychologische Theorien. Auch die Forschungzu Aufgaben ist bislang eher kognitionspsychologisch orientiert. Vor diesem Hintergrund knüpft der vorliegende Beitrag an die allgemeindidaktische Aufgabenforschung an. Allerdings erwies sich der Begriff der Aufgabe im Laufe des Forschungsprozesses als zu eng bzw. voraussetzungsvoll und wurde daher zugunsten des Konzepts der Schüleraktivitäten erweitert. Die zentrale Frage der explorativen Studie lautet demnach, wie Lehrerinnen und Lehrer Schüleraktivitäten planen. Die Überlegungen wurden dabei mit der Methode des Lauten Denkens erfasst und qualitativ inhaltsanalytisch ausgewertet. Erste Ergebnisse zeigen, dass Lehrerinnen und Lehrer zwar implizit in ihrer Planung einige der Dimensionen berücksichtigen, die mit allgemeindidaktischen Modellen in Einklang stehen, dass aber noch ungenügend erforscht wurde, wie Schüleraktivitäten in den subjektiven Planungsüberlegungen vorkommen.}}, author = {{Koch, Barbara and Koch-Priewe, Barbara and Köker, Anne and Kullmann, Harry and Pineker, Anna and Störtländer, Jan Christoph}}, isbn = {{978-3-3840-1172-5}}, journal = {{Jahrbuch für Allgemeine Didaktik}}, keywords = {{Unterrichtsplanung, Schüleraktivitäten, kritisch-konstruktive Didaktik}}, pages = {{267–277}}, title = {{{Schüleraktivitäten in den Planungsüberlegungen von Lehrerinnen und Lehrern: Eine explorative Studie zur Didaktik im Kontext der kritisch-konstruktiven Didaktik}}}, volume = {{3}}, year = {{2013}}, } @inbook{30990, abstract = {{Die Kooperation von Lehrkräften wird als ein zentrales Merkmal „guter Schulen“ eingestuft. Gleichwohl sind die zugehörigen Befunde mitunter wi- dersprüchlich. Vor dem Hintergrund eines theoretischen Wirkungsmodells referiert der vorliegende Beitrag sowohl bestätigende als auch relativierende Ergebnisse im Hinblick auf die Bedeutung der Lehrerkooperation für die Schulleistung, welche ihrerseits zunächst als Indikator des Erfolgs kumulati- ver Bildungsprozesse theoretisch gefasst wird. Bestätigende Befunde lassen sich etwa im Hinblick auf einen Konsens zwi- schen Lehrkräften bei der Umsetzung des Curriculums, den Lerngelegenhei- ten für Lehrkräfte oder den fachdidaktischen Impulsen innerhalb von Kolle- gien ausmachen. Relativierende Hinweise liefern beispielsweise – vor dem Hintergrund einer elaborierten Kooperationskultur – die häufig erwartungs- widrig schlechten Schulleistungen an Gesamtschulen sowie die fehlenden Effekte der Kooperationspraktiken auf das kumulative Kompetenzniveau in Deutsch und Englisch gemäß der DESI-Studie. Die aufgezeigten Perspektiven für die Forschung beziehen sich u.a. auf eine präzisere Erfassung solcher Faktoren des Unterrichts, die einerseits durch Lehrerkooperation verbessert werden können und andererseits in großer Proximität zum Schülerlernen stehen, zum Beispiel die kognitive Aktivierung.}}, author = {{Kullmann, Harry}}, booktitle = {{Professionalität und Kooperation in Schulen. Beiträge zur Diskussion über Schulqualität}}, editor = {{Keller-Schneider, Manuela and Albisser, Stefan and Wissinger, Jochen}}, isbn = {{978-3-7815-1891-9}}, pages = {{123–137}}, publisher = {{Klinkhardt}}, title = {{{Der Zusammenhang von Lehrerkooperation und Schulleistung – Zentrale Befunde und Perspektiven für die Forschung}}}, year = {{2013}}, }