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In dieser Arbeit wird untersucht, ob es möglich ist, mit den Mitteln der Theoretischen Physik mehr auszusagen über das, was sich unter dem Vakuum, aus dem der Urknall erfolgte, verstehen lässt. Hierbei wird deutlich, dass es sich nicht mehr um eine Theorie im eigentlichen Sinne, also um widerlegbare Aussagen handeln, sondern stattdessen um eine Art Modell, das nur anhand von Indizien auf seine Tauglichkeit geprüft werden kann, indem z. B. bisher unbekannte Vorhersagen bestätigt werden oder nicht. Eine solche bisher unbekannte fundamentale Aussage ist, dass dieses Modell zum Ergebnis hat, Schwarze Riesenlöcher entstehen mit dem Freisetzen Dunkler Materie als erstes nach dem Urknall und sind für die Strukturierung des Universums maßgeblich. Beim Begründen dieses Modells wird auf die Methodik in der Veröffentlichung über die mögliche Anatomie Schwarzer Löcher zurückgegriffen. Allerdings konnte in jener Arbeit die mathematische Möglichkeit des Vakuums lediglich als Existenz zweier Antipoden, Energie und Dunkler Energie, am gleichen Ort genannt, aber kein physikalischer Weg dazu aufgezeigt werden. Dort hieß es „Zur Erklärung des Vakuumzustands sehe ich keine Möglichkeit, weil er durch den simplen Zusammenhang, dass gleichviel Energie beider Arten am gleichen Ort sich gegenseitig auslöschen, also von jeder der beiden Energiearten einzeln aus betrachtet praktisch nicht mehr vorhanden ist, mathematisch geradezu trivial, aber physikalisch nicht erklärbar scheint.“ Hier wird nun eine mögliche physikalische Lösung aufgezeigt, die aber ein Entstehen der G-Bosonen erst nach dem Urknall, wie dort noch angenommen, ausschließt. Jetzt muss vielmehr angenommen werden, dass die G-Bosonen bereits im Vakuum existieren und als Dunkle Materie der Gegenpart zur Dunklen Energie sind. Es wird gezeigt, dass sehr wohl zwei sich vollständig kompensierende Dinge, die sich auch noch abstoßen, dennoch einen stabilen Zustand haben können und alle Eigenschaften, die physikalisch von einem Vakuum erw

Durch die Lebenszyklusanalyse von Bauwerkintegrierten Photovoltaik(BIPV)-Fassaden werden deren ökologische Vorteile gegenüber konventionellen Fassadenlösungen aufgezeigt. Die frühzeitige Analyse zu Beginn des Planungsprozesses ermöglicht es, die individuellen Potentiale von Baukörpern zu ermitteln und ermöglicht sichere Planungsentscheidungen durch Kennwerten. In dem Beitrag erfolgen Lebenszyklusanalysen an einem Fallbeispiel mit unterschiedlichen Betrachtungsebenen und methodischen Ansätzen. Es wird geprüft, welche Ansätze die Entscheidungsfindung von Architekt:innen und Planer:innen im Entwurfsprozess am besten unterstützen. Außerdem werden anwendungsbezogenen Erkenntnisse und Randbedingungen bei der Bilanzierung der Treibhausgasemissionen über den gesamten Lebenszyklus von BIPV-Fassaden identifiziert., Life cycle analysis of building-integrated photovoltaic (BIPV) façades demonstrates their ecological advantages over conventional façade solutions. The early analysis at the beginning of the planning process makes it possible to determine the individual potential of building structures and enables reliable planning decisions based on characteristic values. In this article, life cycle analyses are carried out using a case study with different perspectives and methodological approaches. It is examined which approaches best support the decision-making of architects and planners in the design process. In addition, practical findings and boundary conditions for balancing greenhouse gas emissions over the entire life cycle of BIPV façades are identified.

Die Herkunft galaktischer sehr hochenergetischer und ultrahochenergetischer kosmischer Strahlung bleibt rätselhaft, aber Studien weisen auf zahlreiche galaktische Quellen namens PeVatrons hin, die Teilchen auf Petaelektronenvolt-Energien beschleunigen können, darunter Pulsarwindnebel, Supernovareste und Mikroquasare. Die Untersuchung der Gammastrahlung bei Giga- und Teraelektronenvolt-Energien bietet entscheidende Einblicke in ihre Eigenschaften und erweitert unser Verständnis hochenergetischer astrophysikalischer Phänomene. Diese Arbeit analysiert Daten des VERITAS-Gammastrahlenobservatoriums, bestehend aus vier 12-Meter-Tscherenkow-Teleskopen in Arizona, um ein umfassendes Verständnis von zwei galaktischen Quellen zu liefern: MGRO J1908+06, ein potenzieller PeVatron-Kandidat, und SS 433, ein Mikroquasar. MGRO J1908+06 wurde bereits in verschiedenen Wellenlängen untersucht, wobei mehrere potenzielle Ursprünge der Strahlung identifiziert wurden. Diese Arbeit führt eine umfassende Neuuntersuchung seiner ausgedehnten Gammastrahlenemissionen durch, um präzisere Abschätzungen des Gammastrahlenflusses zu liefern und frühere Ergebnisse zu aktualisieren. Die Untersuchung deutet auf einen möglichen Ursprung der Gammastrahlung sowohl aus einem Relikt eines Pulsar-Windnebels als auch aus einem neuen Pulsar-Windnebel im Feld von MGRO J1908+06 hin. Erstmals wird in den VERITAS-Daten eine signifikante Gammastrahlenemission von SS 433 festgestellt. Es werden die Gammastrahlen der Jets bei größeren Abständen und ihre Morphologie untersucht, und TeV-Spektren werden generiert. Modelle zeigen einen leptonischen Ursprung dieser Emissionen, ohne dass eine signifikante Gammastrahlenemission in der Nähe des Schwarzen Lochs oder Anzeichen für Variabilität beobachtet werden. Ausblickend präsentiert die Arbeit Untersuchungen zur Optimierung der Eigenschaften des Cherenkov-Teleskop-Array Observatoriums, mit Fokus auf die Platzierung von Illuminatoren und Abschattungseffekte zwischen Teleskop, The origins of galactic very-high energy and ultra-high energy cosmic rays remain elusive. Recent studies propose the existence of PeVatrons, galactic sources capable of accelerating particles to Petaelectronvolt energies, such as pulsar wind nebulae, supernova remnants, and micro-quasars. Exploring gamma-ray emission at Giga- and Teraelectronvolt energies offers crucial insights into their properties, enriching our understanding of high-energy astrophysical phenomena. This thesis focuses on analysing data from the VERITAS gamma-ray observatory, comprising four 12-meter imaging atmospheric Cherenkov telescopes in Arizona. Employing 3D maximum-likelihood analysis methods, the study aims to provide a comprehensive understanding of two extended galactic sources: MGRO J1908+06, a potential PeVatron candidate, and SS 433, a microquasar. MGRO J1908+06, though unidentified, has been scrutinized across various wavelengths, with several potential counterparts identified previously. This thesis undertakes a re-analysis of its extended gamma-ray emission, leveraging updated analysis methods and recent VERITAS observations. The improved analysis method provides a more accurate estimate of the gamma-ray flux, revising prior VERITAS flux estimates and suggesting a scenario involving both relic and new pulsar wind nebulae. Regarding SS 433, significant gamma-ray emission is detected in VERITAS data for the first time. The morphological properties of the gamma-ray emission regions seen at larger distances along the jets are examined, and their TeV spectra are constructed. Modelling supports a leptonic origin of these emissions, with no significant gamma-ray emission observed near the black hole or any indication of variability. Looking ahead, the thesis presents investigations aimed at optimizing the characteristics of the Cherenkov Telescope Array Observatory, focusing on illuminator placement and mutual shadowing effects to enhance telescope positioning within the array.

The IceCube Neutrino Observatory instruments about 1 km3 of deep, glacial ice at the geographic South Pole. It uses 5160 photomultipliers to detect Cherenkov light emitted by charged relativistic particles. An unexpected light propagation effect observed by the experiment is an anisotropic attenuation, which is aligned with the local flow direction of the ice. We examine birefringent light propagation through the polycrystalline ice microstructure as a possible explanation for this effect. The predictions of a first-principles model developed for this purpose, in particular curved light trajectories resulting from asymmetric diffusion, provide a qualitatively good match to the main features of the data. This in turn allows us to deduce ice crystal properties. Since the wavelength of the detected light is short compared to the crystal size, these crystal properties include not only the crystal orientation fabric, but also the average crystal size and shape, as a function of depth. By adding small empirical corrections to this first-principles model, a quantitatively accurate description of the optical properties of the IceCube glacial ice is obtained. In this paper, we present the experimental signature of ice optical anisotropy observed in IceCube light-emitting diode (LED) calibration data, the theory and parameterization of the birefringence effect, the fitting procedures of these parameterizations to experimental data, and the inferred crystal properties., Peer Reviewed

This repository contains the original experimental data plotted in the paper titled "Terrylene on monolayer WS2: coverage-dependent molecular re-orientation and interfacial electronic energy levels" submitted to the journal Materials Advances., Dieses Repository enthält die ursprünglichen experimentellen Daten, die in dem Artikel mit dem Titel „Terrylene on monolayer WS2: coverage-dependent molecular re-orientation and interfacial electronic energy levels“ aufgezeichnet wurden, der bei der Zeitschrift Materials Advances eingereicht wurde. Der Datensatz enthält alle relevanten Roh- und verarbeiteten Daten, die den im Artikel vorgestellten Erkenntnissen zugrunde liegen., This repository contains the original experimental data plotted in the paper titled "Terrylene on monolayer WS2: coverage-dependent molecular re-orientation and interfacial electronic energy levels" submitted to the journal Materials Advances. The dataset includes all relevant raw and processed data that underpin the findings presented in the paper.

Entertaining the possibility of time travel will invariably challenge dearly-held concepts in fundamental physics. It becomes relatively easy to construct multiple logical contradictions using differing starting points from various well-established fields of physics. Sometimes, the interpretation is that only a full theory of quantum gravity will be able to settle these logical contradictions. Even then, it remains unclear if the multitude of problems could be overcome. Yet as definitive as this seems to the notion of time travel in physics, such recourse to quantum gravity comes with its own, long-standing challenge to most of these counter-arguments to time travel: These arguments rely on time, while quantum gravity is (in)famously stuck with the problem of time. One attempt to answer this problem within the canonical framework resulted in the Page–Wootters formalism, and its recent gauge-theoretic reinterpretation as an emergent notion of time. Herein, we will begin a program to study toy models implementing the Hamiltonian constraint in quantum theory, with an aim toward understanding what an emergent notion of time can tell us about the (im)possibility of time travel., Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), Spanish Project, Czech Science Foundation, Marsden Fund, Peer Reviewed

Die konforme Feldtheorie findet in verschiedenen Bereichen Anwendungen, von statistischen Systemen in der Nähe kritischer Punkte bis hin zur Quantengravitation durch die AdS/CFT-Korrespondenz. Diese Theorien unterliegen starken Einschränkungen, die eine systematische nicht-perturbative Analyse ermöglichen. Konforme Defekte bieten eine kontrollierte Möglichkeit, die Symmetrie zu brechen und neue physikalische Phänomene einzuführen, während wichtige Vorteile der zugrunde liegenden konformen Symmetrie erhalten bleiben. Diese Dissertation untersucht konforme Liniendefekte sowohl im schwachen als auch im starken Kopplungsregimes. Es werden zwei verschiedene Klassen von Modellen untersucht. Wir konzentrieren uns zuerst auf die supersymmetrische Wilson-Linie in N = 4 Super Yang-Mills, die als ideales Testfeld für die Entwicklung innovativer Techniken wie dem analytischen konformen Bootstrap dient. Die zweite Klasse besteht aus magnetische Linien in Yukawa-Modellen, die faszinierende Anwendungen in 3d kondensierten Materiesystemen haben. Diese Systeme haben das Potenzial, Phänomene des Standardmodells in einem Niedrigenergieszenario nachzubilden., Conformal field theory finds applications across diverse fields, from statistical systems at criticality to quantum gravity through the AdS/CFT correspondence. These theories are subject to strong constraints, enabling a systematic non-perturbative analysis. Conformal defects provide a controlled means of breaking the symmetry, introducing new physical phenomena while preserving crucial benefits of the underlying conformal symmetry. This thesis investigates conformal line defects in both the weak- and strong-coupling regimes. Two distinct classes of models are studied. First, we focus on the supersymmetric Wilson line in N = 4 Super Yang–Mills, which serves as an ideal testing ground for the development of innovative techniques such as the analytic conformal bootstrap. The second class consists of magnetic lines in Yukawa models, which have fascinating applications in 3d condensed-matter systems. These systems have the potential to emulate phenomena observed in the Standard Model in a low-energy setting.

The article processing charge was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 491192747 and the Open Access Publication Fund of Humboldt-Universität zu Berlin., Data comparison problems are used in teaching and science education research that focuses on students’ ability to compare datasets and their conceptual understanding of measurement uncertainties. However, the evaluation of students’ decisions in these problems can pose a problem: e.g., students making a correct decision for the wrong reasons. Three previous studies, that share the same context and data comparison problem but where participants had increasing conceptual knowledge of measurement uncertainties, are revisited. The comparison shows a troublesome result: increasing conceptual knowledge does not lead to better decision making in the data comparison problem. In this research, we have looked into this apparent discrepancy by comparing and reanalyzing the data from these three studies. We have analyzed students’ justifications by coding them based on the compared quantity and the deciding criterion, giving a highly detailed insight into what they do when comparing the datasets. The results show clear differences in the quality of the justifications across the studies and by combining the results with the decisions, we could successfully identify four cases of correct and incorrect decisions for right or wrong reasons. This analysis showed a high prevalence of correct decisions for wrong reasons in two of the studies, resolving the discrepancy in the initial comparison of these studies. The implication of our analysis is that simply asking students to make a decision in data comparison problems is not a suitable probe to gauge their ability to compare datasets or their conceptual understanding of measurement uncertainties and a probe like this should always be complemented by an analysis of the justification., Peer Reviewed

Zeitabhängige Multimessenger-Astronomie ist die Studie von vorübergehenden astrophysikalischen Phänomenen mithilfe verschiedener Botschafterteilchen und -wellen. Das High Energy Stereoscopic System (H.E.S.S.) ist ein bodengestütztes Teleskop-Array, das Gammastrahlen im Bereich von 30 GeV bis 100 TeV misst. In dieser Arbeit werden drei H.E.S.S.-Programme zur Nachverfolgung von vorübergehenden Phänomenen diskutiert. Zuerst wird das Nova-Programm vorgestellt, zusammen mit der Entdeckung des Ausbruchs von RS Ophiuchi (RS Oph) im Jahr 2021. RS Oph ist eine Nova, welche schon mehrmals ausgebrochen ist. Die Analyse der Nova, zeigt eine klare Detektion über die ersten fünf Nächte sowie eine marginale Detektion bis zu vier Wochen nach dem Ausbruch. RS Oph ist damit das erste galaktische vorübergehende Phänomen, das bei Energien von ~1 TeV detektiert wurde. Eine klare Variabilität des Spektrums wird gezeigt. Eine Diskussion zeigt, dass die beobachteten Gammastrahlen höchstwahrscheinlich durch beschleunigte Protonen innerhalb eines astrophysikalischen Schocks stammt. Die Ergebnisse zeigen eine zeitaufgelöster Teilchenbeschleunigung. Das zweite Programm ist das Gravitationswellen (GW)-Programm. Hier wird die Analyse von vier beobachteten Verschmelzungsereignissen von binären schwarzen Löchern vorgestellt. Es wird keine Detektion gemeldet, stattdessen werden Himmelskarten mit Höchstgrenzen produziert. Die Effektivität der GW-Nachverfolgung mit H.E.S.S. wird diskutiert. Das dritte Programm ist das Pionierprogramm für Gezeiten-Sternzerrissereignisse (TDEs), das in den letzten Jahren etabliert wurde. Herausforderungen des Programms werden diskutiert, und die H.E.S.S.-Nachverfolgung des Ereignisses AT2019uqv wird vorgestellt. Es werden keine Detektionen gemeldet, stattdessen werden obere Grenzen für AT2019uqv angegeben. Abschließend erfolgt ein Vergleich der Programme sowie ein Ausblick auf das nächste Jahrzehnt bodengestützter Gammastrahlenbeobachtungen., Time-domain multi-messenger astronomy is the study of transient astrophysical phenomena using several messenger particles and waves. The High Energy Stereoscopic System (H.E.S.S.) is a ground-based telescope array, which measures very-high-energy gamma rays between 30 GeV and 100 TeV. Within this work, three H.E.S.S. transients follow-up programs and their results are shown. At first, the nova program is shown together with the detection of the 2021 RS Ophiuchi (RS Oph) outburst. RS Oph is a known nova with past eruptions. The analysis of the nova presented in this work shows a clear detection over the first five nights of observations, and a marginal detection two to four weeks after the eruption. RS Oph is thus the first Galactic transient phenomenon detected at ~1 TeV energies. A clear variability of the spectrum is shown. A discussion of the underlying physics concludes, that the observed gamma-ray emission most likely stems from cooled protons accelerated within an astrophysical shock. The results show time-resolved particle acceleration. The second program is the gravitational-waves (GWs) program. Here, the analysis of four observed binary black hole merger events is shown. No detection is reported, and upper limit sky maps are derived instead. The viability of GW follow-up with H.E.S.S. is discussed, and a case is made for a potential counterpart detection. The third program is the tidal disruption event (TDE) program, a pioneered program established at the emergence of the source class within the last few years. Unique challenges of the follow-up program are discussed, and the H.E.S.S. follow-up of the event AT2019uqv is shown. No detection is reported, and upper limits for AT2019uqv are given instead. The interest in follow-up observations of TDEs with gamma-ray instruments is stressed. In conclusion, a comparison of the different programs and their requirements is given, together with an outlook for the next decade of ground-based gamma-ray observations.

In dieser Arbeit untersuchen wir dualitätsinvariante höher-abgeleitete (alpha') Korrekturen an effektiven Stringtheorien mit niedriger Energie. Wir beschränken uns auf den universellen masselosen Sektor, bestehend aus Graviton, B-Feld und Dilaton, und spezialisieren uns auf Hintergründe mit d abelschen Isometrien, die O(d, d)-Invarianz genießen, und schließen Szenarien wie Kosmologie und Schwarze Löcher als Spezialfälle ein. Es wird erwartet, dass die O(d, d)-Symmetrie für beliebige Ableitungsordnungen erhalten bleibt, eine Tatsache, die Hohm und Zwiebach dazu motivierte, die kosmologische Klassifikation zu finden. Eine solche Konstruktion parametrisiert eine große Klasse rein zeitabhängiger dualitätsinvarianter Theorien für alle Ableitungsordnungen in Form einiger Koeffizienten. Stringtheorien stellen einzelne Punkte in diesem Theorieraum dar, die durch bestimmte Konfigurationen dieser Koeffizienten bestimmt werden. Wir berechnen die ersten Koeffizienten mit zwei Methoden: Verdichtungen und Beta-Funktionsberechnungen aus einer kosmologischen Weltenblattaktion. Anschließend untersuchen wir die Hohm-, Siegel- und Zwiebach-Theorie (HSZ) im kosmologischen Hintergrund, die die masselosen Stringmoden und neuartige massive Felder kodiert. Wir integrieren letztere heraus, um eine effektive Theorie für die masselosen Felder zu erhalten und lesen die entsprechenden Koeffizienten ab. Anschließend behalten wir die massiven Felder bei, finden eine zweifach abgeleitete Neuformulierung der Theorie, bestimmen die alpha'-genauen Friedmann-Gleichungen und erforschen die spannungsfreie Grenze. Wir überprüfen die Klassifikation für FRW-Hintergründe und stellen fest, dass alle Korrekturen trivial sind. Wir erweitern die Klassifikation auf zweidimensionale Hintergründe mit zeitähnlicher Isometrie, einem Raum, der Lösungen für schwarze Löcher zulässt. Wir finden alpha'-deformierte Schwarze Löcher mit und ohne Singularitäten. Letztere entsprechen regulären Kosmologien., In this thesis we study duality-invariant higher-derivative (alpha') corrections to string low energy effective theories. We restrict to the universal massless sector, consisting of the graviton, B-field and dilaton, and specialize to backgrounds with d abelian isometries, which enjoy O(d, d)-invariance and contain scenarios such as cosmology and black holes as particular cases. The O(d, d)-symmetry is expected to be preserved to arbitrary orders in derivatives, a fact that motivated Hohm and Zwiebach to arrive at the cosmological classification. Such construction parameterizes a large class of purely-time dependent duality-invariant theories to all orders in derivatives in terms of a countable infinite number of coefficients. String theories represent single points in this theory space, determined by specific configurations of these coefficients. We compute the first coefficients by following two methods: compactifications and beta-function computations from a worldsheet action already in cosmological backgrounds. We then study the Hohm, Siegel, and Zwiebach (HSZ) theory in cosmological backgrounds, which encodes the massless string modes plus novel massive fields. We integrate out the latter to arrive at an effective theory for the massless fields and read the corresponding coefficients. We then keep the massive fields, find a two-derivative reformulation of the theory, determine alpha'-exact Friedmann equations and explore the tensionless limit. Coming back to generic duality-invariant theories, we revisit the classification for FRW backgrounds and find that all corrections are trivial. We extend the classification to two-dimensional backgrounds with time-like isometry, a space that admits black-hole solutions. We prove that the dual of a solution with a regular horizon must have a curvature singularity, and find alpha'-deformed black holes with and without singularities. The latter correspond to regular cosmologies.

Die Erforschung von Gravitationswellen hat unsere Sicht auf das Universum revolutioniert. Mit dem bevorstehenden Start von LISA, einem Weltraum-Gravitationswellendetektor, und neuen Berichten über Hinweise auf einen Gravitationswellenhintergrund im Nanohertz-Bereich aus Pulsar Timing Array (PTA)-Experimenten, eröffnen sich neue Möglichkeiten und Herausforderungen. Diese Dissertation entwickelt innovative Datenanalysetechniken und Wellenformmodelle, um Erkenntnisse aus diesen Beobachtungen zu gewinnen. Ein Schwerpunkt liegt auf der Untersuchung von Extreme Mass Ratio Inspirals (EMRIs) durch LISA. Diese Quellen bestehen aus kleinen, kompakten Objekten, die sich um ein zentrales Schwarzes Loch bewegen. Die Wellenformen von EMRIs bieten die Möglichkeit präziser Parametermessungen, sind jedoch aufgrund ihrer langen Signaldauer und harmonischen Komplexität schwer zu berechnen. Wir präsentieren die Implementierung einsatzbereiter EMRI-Wellenformen im Frequenzbereich für Grafikprozessoren (GPUs) und zentrale Recheneinheiten (CPUs). Zudem untersuchen wir das wissenschaftliche Potenzial von EMRIs innerhalb von Akkretionsscheiben, erforschen den Einfluss von Umwelteffekten mittels bayesianischer Methoden und bewerten die Multimessenger-Aussichten dieser Systeme. Im PTA-Bereich entwickeln wir Methoden zur Optimierung der Datenkombinationen für PTA-Analysen und tragen zum European Pulsar Timing Array bei, indem wir alternative Sampling-Pipelines für die Analyse von Gravitationswellenhintergründen und individuellen Quellen implementieren. Mit transdimensionalen Sampling-Methoden suchen wir nach einzelnen supermassiven Schwarzen Löchern und bewerten deren Signifikanz. Diese Dissertation trägt zur Weiterentwicklung der Gravitationswellenastronomie bei, indem sie neue Methoden und Modelle entwickelt, die tiefere Einblicke in die kosmischen Phänomene ermöglichen, die von LISA- und PTA-Beobachtungen erfasst werden., Gravitational wave astronomy has reshaped our understanding of the cosmos. As we look towards the future launch of LISA, a space-based gravitational wave detector, and analyze recent evidence of a nanohertz gravitational wave background from Pulsar Timing Array (PTA) experiments, new opportunities and challenges emerge. This thesis delves into developing novel data analysis techniques and waveform models to extract information from these observations. Focusing on LISA, we delve into Extreme Mass Ratio Inspirals (EMRIs). These sources consist of small compact objects spiralling into massive black holes at the centres of galaxies. Their observations are expected to provide precise parameter measurements for these systems. However, EMRI waveform generation poses challenges due to the long signal duration and large harmonic content. For the first time, we provide a fast implementation of EMRI waveforms in the frequency domain, suitable for both graphics processing units (GPUs) and central processing units (CPUs). In addition, we explore the scientific potential of EMRIs embedded in accretion disks. Employing Bayesian inference, we investigate the measurability of environmental effects and explore these systems' multimessenger prospects. Transitioning to PTA, we develop methods to optimize data combinations for PTA analyses. We present our contributions to the second data release of the European Pulsar Timing Array collaboration, which consists of implementing alternative sampling pipelines for gravitational wave background and individual source analyses. Using trans-dimensional sampling methods, we search for individual supermassive black hole binaries and assess their significance. The burgeoning field of gravitational wave astronomy has the potential to transform our understanding of the Universe. The work in this thesis develops new approaches that will facilitate the delivery of the best possible scientific results from current and future gravitational wave observat

During the past few decades, abundant evidence for physics beyond the two standard models of particle physics and cosmology was found. Yet, we are tapping in the dark regarding our understanding of the dark sector. For more than a century, open problems related to the nature of the vacuum remained unresolved. As well as the traditional high-energy frontier and cosmology, technological advancement provides complementary access to new physics via high-precision experiments. Among the latter, the Casimir And Non-Newtonian force EXperiment (Cannex) has successfully completed its proof-of-principle phase and is going to commence operation soon. Benefiting from its plane parallel plate geometry, both interfacial and gravity-like forces are maximized, leading to increased sensitivity. A wide range of dark sector forces, Casimir forces in and out of thermal equilibrium, and gravity can be tested. This paper describes the final experimental design, its sensitivity, and expected results., This research was funded by the Austrian Science Fund (FWF) under grant No. P 36577-N and P 34240-N., Austrian Science Fund (FWF), Peer Reviewed

Die Ladungsinjektion (-extraktion) an einer Schnittstelle spielt in der organischen Elektronik eine entscheidende Rolle, da sie die Leistung des Bauelements stark beeinflusst. Eine der effizientesten Methoden zur Optimierung der Energiebarrieren für die Injektion ist die Modifikation der Austrittsarbeit der Elektroden. In dieser Dissertation untersuchen wir die Modifikation der Austrittsarbeit von Au(111) durch dithiol-terminiertes Polyethylenglykol (PEG(thiol)) sowie deren Abhängigkeit von der Anzahl der PEG-Wiederholungseinheiten. In beiden Fällen beobachten wir, dass die Austrittsarbeit des Au(111) durch eine Monoschicht PEG(thiol)-Moleküle reduziert wird. Unsere Berechnungen zeigen, dass diese Änderung der Austrittsarbeit hauptsächlich durch (i) die Ladungsumlagerung aufgrund der Chemisorption und (ii) das intrinsische Dipolmoment der PEG(thiol)-Monoschicht verursacht wird. Die Größe des letzteren Beitrags hängt spürbar von der Anzahl der Wiederholungseinheiten ab und bewirkt somit eine Variation in der Reduktion der Austrittsarbeit. Das oszillatorische Verhalten spiegelt einen ausgeprägten Odd-Even-Effekt wider. Dadurch kann die Austrittsarbeit der Metallelektrode unter Berücksichtigung des Odd-Even-Effekts gesteuert werden. Die Konvergenz der selbstkonsistenten Felditeration für unsere Systeme ist nicht garantiert. Um die Konvergenz zu verbessern, schlagen wir die Verwendung eines speziell auf die FP-LAPW-Methode zugeschnittenen Mischalgorithmus vor. In einem auf Ag(111) basierenden System zeigt sich, dass eine Struktur mit drei Leerstellen in der Substratschicht besonders stabil ist. Dabei ist eine kontinuierliche Abnahme der Austrittsarbeit des Ag(111) feststellbar. Ähnlich wie beim Au(111) manifestiert sich der Odd-Even-Effekt, der auf das Dipolmoment der Molekularschicht zurückzuführen ist., Charge injection (extraction) at an interface plays a crucial role to organic electronics because this injection (extraction) heavily affects the device performance. One of the most efficient way to optimize energy barriers of the injection (extraction) is modifying the work function of electrodes. In this dissertation, we investigate the modification of work function of Au(111) and Ag(111) induced by the dithiol-terminated polyethylene glycol (PEG(thiol)) as well as a dependence of the work function change on different numbers of PEG repeat units. We find that the work function of the Au(111) is reduced by a monolayer of PEG(thiol) molecules. Overall, our calculations indicate that the work function change is mainly induced by (i) the charge rearrangement due to chemisorption and (ii) the intrinsic dipole moment of the PEG(thiol) monolayer. The magnitude of the latter contribution noticeably depends on the number of repeat units and, thus, causes a variation in the reduction of the work function. The oscillatory behavior reflects a pronounced odd-even effect. As a result, the work function of the metal electrode would be controlled by considering the odd-even effect. Unfortunately, the convergence of the self-consistent field iteration is not guaranteed for our investigated systems. To make the smooth convergence, a mixing algorithm, which is applicable to FP-LAPW method, is devised. We add the Kerker preconditioner as well as further improvements to Pulay’s direct inversion in the iterative subspace. Using this method, one can avoid charge sloshing and noise in the exchange-correlation potential. This method is also implemented in the exciting code. We find the decrease of the work function of the Ag(111) surface is always presented. Similar to the Au(111) case, the odd-even effect is revealed, arising from the dipole moment of the molecular layer.

The article processing charge was funded by the Open Access Publication Fund of Humboldt-Universität zu Berlin., Missing transverse momentum is a crucial observable for physics at hadron colliders, being the only constraint on the kinematics of “invisible” objects such as neutrinos and hypothetical dark matter particles. Computing missing transverse momentum at the highest possible precision, particularly in experiments at the energy frontier, can be a challenging procedure due to ambiguities in the distribution of energy and momentum between many reconstructed particle candidates. This paper describes a novel solution for efficiently encoding information required for the computation of missing transverse momentum given arbitrary selection criteria for the constituent reconstructed objects. Pileup suppression using information from both the calorimeter and the inner detector is an integral component of the reconstruction procedure. Energy calibration and systematic variations are naturally supported. Following this strategy, the ATLAS Collaboration has been able to optimise the use of missing transverse momentum in diverse analyses throughout Runs 2 and 3 of the Large Hadron Collider and for future analyses., Peer Reviewed

Topological Insulator (TI) nanowires have attracted attention in recent years, not only because of the novel physics that are to be discovered in such systems, but also because they are a possible platform to realize Majorana fermions and topological quantum computation. In this thesis, electronic transport in TI nanowires is investigated. Bulk-insulating nanowires are grown by the vapor-liquid-solid method from the ternary topological insulators (Bi_{1-x}Sb_x)_2Te_3 ("BST") and Bi_2(Te_xSe_{1-x})_3 ("BTS"). At cryogenic temperatures, the particular properties of their quantum-confined topological surface states are studied through electrostatic gating, which gives rise to characteristic restiance oscillations originating from their quantized sub-band structure. In magnetic fields, Aharonov-Bohm-like oscillations are measured, and their peculiar pi-shift is observed. Furthermore, superconductivity is induced by the proximity effect from Nb and V (in the structure TiVTiAl) in nanowire Josesephson junction devices. The proximitization is characterized and interplay with the topological surface states is investigated. First attempts at tunneling spectroscopy on the proximitized TI nanowires are made.

In this doctoral thesis, new experimental findings on the nuclear structure of 130Cd and simulations for the HISPEC slowed down beam (SDB) campaign are presented. In this work 131In and 130Cd are investigated in an inflight-decay spectroscopy experiment performed at the RIKEN RIBF facility. 131In and 130Cd were produced in fragmentation fission reactions and proton knockout reactions with 9Be targets and were identified in the BigRIPS and ZeroDegee spectrometers. The excitation energies and half-lives of excited nuclear states populated in proton knockout reactions were inferred from the energies of gamma-rays emitted in their decays. This was achieved by comparing the energies of gamma-rays detected in the HiCARI array to Monte-carlo simulations. Two new gamma-decays were observed in 130Cd which were attributed to two previously unobserved excited states. These results were interpreted in the context of a nuclear shell model calculation which was shown to successfully describe the structure of 130Cd including the newly observed states. Simulations of the HISPEC SDB campaign, proposed to study the nuclear structure of rare-isotope beams produced in the SuperFRS at FAIR with AGATA, were produced. The transport of 64Ni through the SuperFRS and its slowing from 233 MeV/u to the Coulomb barrier in a 27Al degrader was simulated using the MOCADI ion-transport code. The kinematic reconstruction and identification of ions after the degrader was simulated in a Geant4 simulation of the proposed SDB setup. The performance, positioning and geometry of SDB detectors, required for the identification of ions and the reconstruction of the energies of gamma-rays emitted in the gamma-decay of ions excited in Coulomb excitations with a thin 197Au target, was evaluated. SDB experiments with the proposed setup were found to be feasible under the conditions identified as required of SDB detectors for experiments lasting five days with at least 10^4 p/s available 64Ni beam intensity.

Organic electronics are at the forefront of modern optoelectronic technologies. Their photophysical properties are determined not only by the organic molecules chosen, but also by their intermolecular interactions in an aggregated phase. These interactions have multiple fingerprints on ultrafast timescales, which can lead to deeper understanding of these materials and higher performance devices. The scope of this work covers the ultrafast and steady-state photophysical and excitonic properties of aggregates and blends based on the squaraine molecules nBSQ and ProSQ-C16, targeted for photodetection, photovoltaic and chiroptical applications. In detail, we utilized ultrafast transient absorption spectroscopy and steady-state absorption and emission spectroscopy, employing both experimental and simulation approaches. The use of a white light supercontinuum probe in transient absorption enabled us not only to study the lifetime of excitons, but also reveal their physical nature. Complementary to the experimentally obtained spectra, lightweight simulations of both steady-state and ultrafast transient spectra were employed. This approach unfolded the underlying large-scale aggregate structure, revealing the structure-property relationships in squaraine-based molecular aggregates.

For non-sexually reproducing organisms such as bacteria, natural transformation, a common mode of horizontal gene transfer (HGT), plays an important role in increasing genetic diversity, spreading beneficial mutations and curing deleterious ones. However, little is known about the genome-wide barriers, the effects of transformation on fitness and the role of the genetic background of the strains. In the first project, we elucidate the genome-wide barriers of transformation and their dependence on the genetic distance between donor and recipient. We conduct replacement accumulation experiments with Bacillus subtilis as recipient and different Bacillus species as well as a Geobacillus species as donors. For 20 cycles, we allow the recipient to transform for two hours in presence of donor DNA, ensure minimal selection by plating the hybrids directly after transformation, and apply a single cell bottleneck by selecting a monoclonal hybrid for the start of the next cycle. Following cycle 10 and 20, the DNA of the hybrids is sent for whole genome sequencing and the fitness is measured by competition experiments. By pooling all hybrids, we find 96% of core genes affected by replacements when supplying B. subtilis with Bacillus spizizenii DNA, indicating an almost unrestricted exchange between closely related species. In the less-related species Bacillus atrophaeus, we find replacement primarily in regions with high sequence identity, with an overrepresentation of ribosomal genes. A comparison of all donor-recipient pairs reveals an exponential relationship between core genome identity and transfer rate. Core genome identity also affects the length of replaced segments. At a low rate, the replacements entail insertions and deletions of accessory regions. We conclude that transformation between closely related species is strongly dependent on sequence identity and is dominated by replacements. In the second project, we characterize the fitness effects of transformation. To t

This thesis focuses on the development of superconducting planar components for the CCAT Heterodyne Array instrument (CHAI). Planned to operate in two bands simultaneously, CHAI will feature two independent 64-pixel arrays covering 455 - 495 GHz (Low Frequency Array) and 780 - 820 GHz (High Frequency Array). The basic unit composing the arrays are 4-pixel waveguide blocks, fabricated in split block technology and designed to house four planar mixers fabricated on silicon substrates, which are suspended inside waveguide cavities. Each 4-pixel block also contains the local oscillator distribution network. The two topics of this thesis are the development of a power divider based on superconducting planar chip technology to perform the 1-to-4 power division for the LFA and the design of an integrated balanced mixer for the HFA. For the power division, a total of five different power dividers were designed in planar technology and fabricated in the I. Physikalisches Institut (Ph.I) microstructure fabrication laboratory. The individual components of the balanced mixers for the HFA have been designed and simulated, but could not be manufactured yet due to time constraints. Due to the impossibility of Vector Network Analyzer (VNA) measurement to characterise the power dividers fabricated in this work, the SIS junctions found in the Integrated BAlanced Mixer (IBAMI), the mixer of choice for the LFA, are used as power detectors. The experimental setup is then composed of two IBAMI connected by waveguides to the power divider’s outputs. This configuration has the advantage that it represents half of the 4-pixel block for CHAI, allowing for testing the components meant to populate the LFA in a simpler setup. This setup allows only for power division measurements with no possibility for direct measurement of the reflections at the waveguide ports of the power divider. Four units of the 2-pixel test block were fabricated in the mechanical workshop of the I. Physikalisches Instit

The Kitaev Quantum Spin Liquid (QSL) is a theoretical phase of matter proposed by physicist Alexei Kitaev in 2006. It is characterized by the absence of conventional long-range magnetic order in the magnetic moments of electrons, even at absolute zero temperature, distinguishing it from traditional magnetic systems. This QSL phase arises from anisotropic, direction-dependent spin interactions among spin-1/2 electrons on a two-dimensional honeycomb lattice. alpha-RuCl3 has emerged as a promising candidate for the observation of the QSL phase due to its direction-dependent exchange interactions. However, the presence of isotropic Heisenberg exchange interactions results in a zigzag antiferromagnetic order below 7 K, with additional complexity introduced by anisotropic off-diagonal interactions. Despite these challenges, numerous studies suggest that a QSL phase might be stabilized in the field-induced phase of the material. In this study, we employ Raman scattering to investigate alpha-RuCl3. We begin with angle-resolved Raman scattering to verify the crystal symmetry. Subsequently, we explore the field-induced phase, observing a transition in the Raman response from a featureless, gapless broad continuum and weak antiferromagnetic magnons in the magnetically ordered phase to sharp magnetic excitations and a gapped continuum in the disordered phase. Additionally, helicity-resolved Raman scattering with in-plane magnetic fields reveals the chiral nature of magnetic and phononic excitations. This technique identifies a distinct field regime between 7.5 and 10.5 T, correlating with the proposed stabilization of the QSL phase. Our study underscores the significance of the field-induced phase, providing insights into complex interactions such as chirality-selective hybridization between the continuum and phonons, and a particular non-reciprocal hybridized feature arising from phonon-magnon interaction.

During antigenic evolution, a virus alters its presentation to the immune system, reducing the ability of the immune system to recognize and protect against the virus. Those viruses that most successfully escape from immune protection are selected for in the evolutionary process. These viruses are most likely to predominate in the future viral population. The selection pressures that shape this evolution are computable from models that use molecular input data on the interaction between the virus and the immune system. Given these selection pressures, future evolutionary trajectories of viruses can be predicted. These predictions help the timely identification of emerging variants and inform the most protective antigenic composition of vaccinations. Alternatively, given frequency trajectories of viral evolution, key parameters can be learned that describe the molecular interaction between the virus and the immune system. These parameters describe the effects of immune therapy while considering the evolutionary response of the virus explicitly. In this thesis, I discuss the antigenic evolution of three fast-evolving viruses. First, I analyze the in vivo antigenic escape evolution of HIV-1 from a broadly neutralizing antibody. In this analysis, I use data from clinical trials to infer key fitness parameters that determine escape evolution across multiple hosts. Second, I present an antigenic model to predict the evolutionary trajectories of SARS-CoV-2. The model is the first to use human antigenic data to predict viral evolution. In this work, I combine genetic, epidemiological, and antigenic data to model the population immunity that determines viral fitness. The fitness model can predict the short-term evolution of SARS-CoV-2, as well as predict the antigenic profile of future escape variants. Finally, I present a set of methods for the evolutionary analysis of influenza. It contains methods on evolutionary tracking, inference of selection, inference and tracking of

Low-level mixed-phase clouds (LLMPCs) shroud large portions of Earth’s surface at high latitudes. They have been shown to dramatically affect the surface energy budget, yet, large uncertainties in their model representation remain, both in climate simulations, and in numerical weather prediction. Both computational limitations and poor understanding of a number of processes taking place in LLMPCs are thought to give rise to such uncertainties. In particular, precipitation formation processes have been relatively understudied in LLMPCs, and reaching a refined understanding is expected to lead to an improvement in model performance, as precipitation determines the cloud’s mass sink, and hence lifetime. In this dissertation, precipitation formation processes are investigated in LLMPCs at the high Arctic site of Ny-Ålesund, based on long-term cloud radar observations. Cloud radars are in fact especially suited for ice microphysical studies, due to the wide spectrum of observational fingerprints of ice microphysical processes that they provide. Doppler radar observations provide information on dynamics, multi-frequency radar observations on ice particle size, and polarimetric radar observations on particle shape and concentration. Radar data are combined with thermodynamic information, which further allows to discriminate between ice microphysical processes, due to their high sensitivity to temperature. In the first part of the dissertation, the relevance of the aggregation process for LLMPCs at Ny-Ålesund is assessed. Aggregation occurs when ice particles collide to form larger ice particles. A long-term dataset of dual-frequency radar observations, as well as thermodynamic information, is used to statistically assess the relevance of aggregation and its sensitivity to varying cloud thermodynamic conditions. The study finds that larger aggregate snowflakes are predominantly produced in LLMPCs whose mixed-phase layer is at temperatures compatible with the growth and subs

Pipeline transport is an efficient method for transporting fluids in energy supply and other technical applications. While natural gas is the classical example, the transport of hydrogen is becoming more and more important; both are transmitted under high pressure in a gaseous state. Also relevant is the transport of carbon dioxide, captured in the places of formation, transferred under high pressure in a liquid or supercritical state and pumped into underground reservoirs for storage. The transport of other fluids is also required in technical applications. Meanwhile, the transport equations for different fluids are essentially the same, and the simulation can be performed using the same methods. In this paper, the effect of control elements such as compressors, regulators and flaptraps on the stability of fluid transport simulations is studied. It is shown that modeling of these elements can lead to instabilities, both in stationary and dynamic simulations. Special regularization methods were developed to overcome these problems. Their functionality also for dynamic simulations is demonstrated for a number of numerical experiments.

Das Ziel dieser Arbeit ist, die elektronischen Eigenschaften von CZTS zu verstehen. Ein leistungsfahigesWerkzeug zu diesem Zweck ist die Rontgen-Nahkanten Absorptions-Spektroskopie (XANES). Die Interpretation von XANES-Spektren komplexer Materialien ist nicht trivial und erfordert daher theoretische Modellierung. Alle Rechnungen in dieser Arbeit wurden mittels der im exciting Code implementierten Linearized-Augmented-Plane- Wave-Methode, welche alle Elektronen gleichberechtigt behandelt, durchgefuhrt. Die genaue Beschreibung der Anregungen von Kernzustanden wird durch ein zweistufiges Verfahren erreicht. Zunachst wird die elektronische Struktur berechnet, indem die Kohn-Sham-Gleichungen (KS) der Dichtefunktionaltheorie (DFT) gelost werden. Die Absorptionsspektren unter Berucksichtigung der Elektron-Loch-Wechselwirkung (e-h) werden durch die Losung der Bethe-Salpeter Gleichung (BSE) der Vielteilchen-Storungstheorie (MBPT) unter Einsatz der KS-Zustonde als Ausgangspunkt beschrieben., The aim of this work is to understand the electronic properties of CZTS. X-ray absorption near edge structure (XANES) is a powerful tool for this purpose. Interpreting XANES of complex materials is nontrivial and thus requires theoretical modeling. Here, all the calculations are performed using an all-electron full-potential augmented plane-wave method as implemented in the exciting code. The accurate description of the core level excitations is performed by a two-step procedure. First, the electronic structure is calculated by solving the Kohn-Sham (KS) equation of density functional theory (DFT). The absorption spectra including electron-hole (e-h) is described by the solution of the Bethe-Salpeter equation (BSE) of many-body perturbation theory (MBPT) using the KS states as starting point.

Neutrinooszillationen sind das einzige Phänomen jenseits des Standardmodells, das experimentell mit hoher statistischer Signifikanz bestätigt wurde. Diese Arbeit präsentiert eine Messung der atmosphärischen Neutrinooszillationen unter Verwendung von acht Jahren an Daten, die zwischen 2011 und 2019 vom IceCube DeepCore-Detektor aufgenommen wurden. Die Ereignisauswahl wurde im Vergleich zu früheren DeepCore-Messungen verbessert, wobei ein besonderes Augenmerk auf ihre Robustheit gegenüber systematischen Unsicherheiten in den Detektoreigenschaften gelegt wurde. Die Oszillationsparameter werden über eine Maximum-Likelihood-Fit an gebinnte Daten in der gemessenen Energie und Zenitwinkel geschätzt, wobei die Erwartungswerte aus gewichteten simulierten Ereignissen abgeleitet werdem. Diese Arbeit diskutiert den Simulations- und Datenauswahlprozess sowie die statistischen Methoden, die verwendet werden, um einen genauen Erwartungswert unter variablen Detektoreigenschaften und anderen systematischen Unsicherheiten zu liefern. Die Messung wird zunächst unter Verwendung des Standardmodells der Drei-Flavor-Oszillation durchgeführt, wobei das atmosphärische Massensplitting und der Mischwinkel auf $\Delta m^2_{32} = 2.42_{-0.75}^{+0.77} \times10^{-3};\mathrm{eV}^2$ und $\sin^2\theta_{23} = 0.507_{-0.053}^{+0.050}$ geschätzt werden. Das Drei-Flavor-Modell wird dann um einen zusätzlichen Masseneigenzustand erweitert, der einem sterilen Neutrino mit Massensplitting $\Delta m^2_{41} = 1;\mathrm{eV}^2$ entspricht und mit den aktiven $\nu_\mu$- und $\nu_\tau$-Flavorzuständen mischen kann. Es wird kein signifikantes Signal eines sterilen Neutrinos beobachtet, und die Mischungsamplituden zwischen den sterilen und aktiven Zuständen werden auf $|U_{\mu 4}|^2 < 0.0534$ und $|U_{\tau 4}|^2 < 0.0574$ bei 90\% C.L. begrenzt. Diese Grenzwerte sind um den Faktor zwei bis drei strenger als das vorherige DeepCore-Ergebnis, und die Einschränkung von $|U_{\tau 4}|^2$ ist die stärkste der Welt., Neutrino oscillations are the only phenomenon beyond the Standard Model that has been confirmed experimentally to a very high statistical significance. This work presents a measurement of atmospheric neutrino oscillations using eight years of data taken by the IceCube DeepCore detector between 2011 and 2019. The event selection has been improved over that used in previous DeepCore measurements with a particular emphasis on its robustness with respect to systematic uncertainties in the detector properties. The oscillation parameters are estimated via a maximum likelihood fit to binned data in the observed energy and zenith angle, where the expectation is derived from weighted simulated events. This work discusses the simulation and data selection process, as well as the statistical methods employed to give an accurate expectation value under variable detector properties and other systematic uncertainties. The measurement is first performed first under the standard three-flavor oscillation model, where the atmospheric mass splitting and mixing angle are estimated to be $\Delta m^2_{32} = 2.42_{-0.75}^{+0.77} \times10^{-3}\;\mathrm{eV}^2$ and $\sin^2\theta_{23} = 0.507_{-0.053}^{+0.050}$, respectively. The three-flavor model is then extended by an additional mass eigenstate corresponding to a sterile neutrino with mass splitting $\Delta m^2_{41} = 1\;\mathrm{eV}^2$ that can mix with the active $\nu_\mu$ and $\nu_\tau$ flavor states. No significant signal of a sterile neutrino is observed and the mixing amplitudes between the sterile and active states are constrained to $|U_{\mu 4}|^2 < 0.0534$ and $|U_{\tau 4}|^2 < 0.0574$ at 90\% C.L. These limits are more stringent than the previous DeepCore result by a factor between two and three and the constraint on $|U_{\tau 4}|^2$ is the strongest in the world.

Der steigende weltweite Energiebedarf treibt die Entwicklung sauberer Energiequellen voran, die dazu beitragen werden, den Verbrauch fossiler Brennstoffe zu reduzieren. Brennstoffzellen und Metall-Luft-Batterien sind vielversprechende Alternativen, um traditionelle fossile Energie zu ersetzen und durch die Reduzierung von O2 an der Kathode grünen Strom zu erzeugen. Aufgrund der langsamen Reaktionsraten der Sauerstoffreduktionsreaktion (ORR) ist hierfür jedoch elektrokatalytisches Material mit geringen Kosten und hoher Effizienz erforderlich. In den letzten Jahrzehnten wurde eine Vielzahl von Materialien als Nicht-Pt-Katalysatoren getestet, von metallfreien Katalysatoren bis hin zu Katalysatoren auf Übergangsmetallbasis. Aufgrund des mangelnden Verständnisses des Reaktionsmechanismus und der Wechselwirkung zwischen Elektrolyt und Elektrokatalysator befinden sich neue Designs stickstoffhaltiger Katalysatoren auf Kohlenstoffbasis jedoch noch in der Entwicklungsphase. Zu diesem Zweck wurden verschiedene (in situ) spektroskopische und elektrochemische Techniken eingesetzt, um die Wechselwirkung zwischen N-dotiertem Kohlenstoff und Elektrolyten sowie die katalytischen Mechanismen zu verstehen. Darüber hinaus weisen die neu entwickelten Katalysatoren für die ORR eine überlegene elektrokatalytische Leistung auf, die in dieser Dissertation ausführlich diskutiert wird. Die Struktur-Leistungs-Beziehung unserer ORR-N-dotierten Kohlenstoffkatalysatoren wurde gründlich untersucht. Diese Forschung zeigt, wie die Kombination fortschrittlicher Spektroskopietechniken, einschließlich In-situ-Spektroskopie und elektrochemischer Charakterisierung, ein tieferes Verständnis der Katalysator-/Elektrolyt-Wechselwirkung, des katalytischen Mechanismus und der optimierten elektrokatalytischen Leistung stickstoffhaltiger Kohlenstoffmaterialien, ORR-Katalysatoren, insbesondere nanoporöser N-dotierter Kohlenstoff, fördern kann Eisen-Stickstoff-codotierte Kohlenstoffmaterialien., Increasing global energy demand drives the development of clean energy sources that will help reduce the consumption of fossil fuels. Fuel cells and metal-air batteries are promising alternatives to replace traditional fossil energy to generate green electricity by reducing O2 at the cathode. However, due to sluggish reaction rates of oxygen reduction reaction (ORR), this requires electrocatalytic material with low cost and high efficiency. Over the last few decades, a variety of materials have been tested as non-Pt catalysts, from metal-free catalysts to transition metal-based catalysts. However, due to the lack of understanding of the reaction mechanism and the interaction between electrolyte and electrocatalysts, new designs nitrogen-containing carbon-based catalysts are still under the development stage. To this aim, a variety of (in situ) spectroscopic and electrochemical techniques to understand N-doped carbon electrocatalysts/electrolyte interaction and catalytic mechanisms have been employed. Moreover, the newly-designed catalysts for ORR demonstrate superior electrocatalytic performance which are discussed in detail in this dissertation. The structure-performance relationship for our ORR N-doped carbon catalysts has been thoroughly investigated. This research highlights how the combination of advanced spectroscopy techniques including in situ spectroscopy and electrochemical characterization may promote a deeper understanding of catalyst/electrolyte interaction, catalytic mechanism and optimized electrocatalytic performance of nitrogen-containing carbon materials ORR catalysts, especially nanoporous N-doped carbon and iron-nitrogen-co-doped carbon materials.

Since their discovery many decades ago, relativistic jets have intrigued and fascinated astronomers. Besides being crucial elements in shaping the Universe as we observe it today, jets are unique laboratories to test and broaden our knowledge in many fields of physics, such as plasma physics and cosmology. This thesis aims at investigating the relativistic jets launched from radio galaxies, a specific class of Active Galactic Nuclei (AGN), with the goal of understanding the jet formation and propagation phenomena, as well as the connection between accretion and ejection. Specifically, the work focuses on NGC 315, a giant radio galaxy whose vicinity and large mass of the central black hole offer a unique opportunity to address these subjects. The study combines two approaches: the analysis of Very Long Baseline Interferometry (VLBI) observations is accompanied by a theoretical study carried out by means of numerical simulations. These are performed using a relativistic magnetohydrodynamic (RMHD) code. The thesis is composed of three introductory chapters followed by three results chapters. In Chapter 1, I introduce the fundamental physical and astronomical concepts concerning AGN, which are central throughout the thesis. In Chapter 2, I describe the basic elements of plasma physics and provide an overview of the state-of-the-art knowledge regarding the theory of jet formation and propagation together with the currently open questions. In Chapter 3, I explain the fundamental concepts concerning the VLBI technique, and how to perform the analysis of VLBI data. Finally, Chapters 4, 5, and 6 present the series of works on NGC 315, with Chapters 4 and 6 focusing on the observational studies and Chapter 5 describing the theoretical one. From the analysis of a multi-frequency and multi-epoch VLBI data set, the extents of the jet collimation and acceleration regions in NGC 315 are suggested to coincide. Namely, the jet is observed to collimate within ~ 0.6 pc from its apex

For decades, physicists have been fascinated by frustrated magnetism. Frustration arises when the pairwise interaction energies between localized magnetic moments in a system cannot be minimized simultaneously. This competition prevents the formation of long range magnetic order even at lowest temperatures and, eventually, leads to the hallmark of frustration in the form of a massive ground state degeneracy accompanied by a finite zero-point entropy. Thus, exotic magnetic analogs of ordinary fluids can be realized, where spins are highly correlated but remain strongly fluctuating. Such spin liquids are linked to remarkable unconventional collective phenomena, most notably emergent gauge fields and fractionalized quasi-particle excitations that can be conceived as magnetic monopoles. In this thesis, we study the dynamics of such quasi-monopoles in the presence of a magnetic field and address the question whether critical fluctuations at a phase transition always slow down equilibration or, conversely, can also help the system to thermalize. Employing large-scale dynamical Monte Carlo simulations, we show that the latter---a critical speeding up---can indeed be observed in two prototypical classical spin systems: dipolar spin ice in pyrochlore magnets and a Coulomb spin liquid in the triangular lattice Ising antiferromagnet. For the former, we also establish a relationship between Monte Carlo time and real time by comparing numerical and experimental data. Another part of this thesis is concerned with systems in which further-neighbor interactions stabilize certain non-coplanar magnetic orders. Such orders are particularly interesting because upon introducing quantum fluctuations, they may possibly melt into a chiral quantum spin liquid. To this end, we study two model systems that turn out to have non-coplanar classical ground states and are motivated by the recent synthesis of a number of Mott insulating square-kagome materials as well as of spin-1/2 maple-leaf latt

In dieser Arbeit wird Terahertzspektroskopie (THz) eingesetzt, um nichtlineare niederfrequente Anregungen von kondensierter Materie zu untersuchen. Insbesondere die Anwendung zweidimensionaler (2D) THz-Spektroskopie ermöglicht es, verschiedene Beiträge zu nichtlinearen Signalen zu entflechten. Zunächst wird die nichtlineare polaronische Antwort solvatisierter Elektronen und umliegenden Lösungsmittelmolekülen in der polaren Flüssigkeit Isopropanol erforscht. Solvatisierte Elektronen werden durch Multiphotonen-Ionisation erzeugt. Longitudinale Polaronoszillationen mit THz-Frequenzen werden während der ultraschnellen Lokalisierung der Elektronen impulsiv angeregt. Die Störung solcher Polaronschwingungen mit einem externen THz-Impuls führt zu nichtlinearen Änderungen der transversalen Polaron-Polarisierbarkeit, die sich in deutlichen Änderungen der Oszillationsphase zeigen. Darüber hinaus wird die Erzeugung monozyklischer THz-Impulse in asymmetrischen Halbleiter-Quantentrögen bei resonanter Intersubband-Anregung im Mittelinfraroten (MIR) demonstriert. Die zeitliche Form des emittierten elektrischen THz-Feldes wird durch die Steuerung der Impulsdauer und des elektrischen Feldes der MIR Impulse verändert. Phasenaufgelöste 2D-MIR-Experimente bestätigen, dass die THz-Emission vorrangig auf einen nichtlinearen Verschiebungsstrom bei Femtosekunden-Intersubband-Anregung zurückzuführen ist. Der Einfluss von Intra- und Interbandströmen auf Symmetrieeigenschaften wird in 2D-THz-Experimenten an Wismut demonstriert. Nichtperturbative langwellige Anregung von Ladungsträgern nahe der L-Punkte führt zu einer anisotropen Ladungsträgerverteilung, die sich in einer hexagonalen Winkelabhängigkeit der pump-induzierten THz Transmission manifestiert. Eine damit einhergehende Symmetrieverringerung für bestimmte elektrische Feldpolarisationen erlaubt die Anregung von Zonenrand-Phononen, welche sich in in oszillierenden Signalen in der nichtlinearen 2D-THz-Antwort manifestieren., This thesis exploits techniques of terahertz (THz) spectroscopy to investigate nonlinear low-frequency excitations of condensed matter. In particular, application of two-dimensional (2D) THz spectroscopy allows to disentangle different nonlinear signal contributions. The nonlinear polaronic response of solvated electrons and their surrounding solvent molecules in the polar liquid isopronal is studied. Solvated electrons are generated via multiphoton ionization. Longitudinal polaron oscillations with THz frequencies are impulsively excited during the ultrafast localization of the electrons. Perturbation of such polaron oscillations with an external THz pulse induces nonlinear changes of the transverse polaron polarizability, reflected in distinct modifications to the oscillation phase as mapped in 2D-THz experiments. Further, the generation of mono-cycle THz pulses from asymmetric semiconductor quantum wells upon resonant intersubband excitation in the mid-infrared (MIR) range is demonstrated. The temporal shape of the emitted THz electric field is modified by controlling pulse duration and peak electric field of the MIR driving pulses. Phase-resolved 2D-MIR experiments confirm that the THz emission is predominantly due to a nonlinear shift current generated upon femtosecond intersubband excitation. The influence of combined intra- and interband currents on symmetry properties, which opens novel quantum pathways for phonon excitation in narrow-band-gap materials, is demonstrated by 2D-THz experiments on bismuth. Nonperturbative long-wavelength excitation of charge carriers close to the L points leads to an anisotropic carrier distribution, reflected in a six-fold azimuthal angular dependence of the pump-induced change of THz transmission. A concomitant symmetry reduction for certain electric-field polarizations allows for the excitation of phonons at the zone boundary which are reflected in oscillatory signals in the nonlinear 2D-THz response.

In den letzten Jahrzehnten haben Tischlaserquellen eine bemerkenswerte Entwicklung durchlaufen. Sie sind nun in der Lage, maßgeschneiderte ultrakurze Mehrfarben-Laserpulse zu erzeugen, die es ermöglichen, die elektronische Dynamik in Materialien auf ihrer natürlichen Zeitskala von Attosekunden zu untersuchen. In dieser Arbeit werden verschiedene Kombinationen von elektrischen Feldern genutzt, von extrem-ultravioletten (XUV) bis nahinfraroten Wellenlängen, um komplexe Elektronendynamiken in Atomen und chiralen Medien zu erforschen, zu rekonstruieren und zu kontrollieren. Dabei werden grundlegende Konzepte der Licht-Materie-Wechselwirkung eingeführt, einschließlich starker Feldprozesse, die im Kern der Attosekundenspektroskopie liegen. Ein Schwerpunkt liegt auf der Nutzung eines XUV-Pulses in Kombination mit einem nahinfraroten Puls, um den Bevölkerungstransfer zu hohen Drehimpulszuständen in Heliumatomen zu untersuchen. Durch Manipulation der Laserparameter wird die Rolle des AC Stark-Effekts von gebundenen Zuständen in der beobachteten Dynamik identifiziert. Weitere Untersuchungen umfassen die Verwendung eines bicirculären elektrischen Feldes zur Induktion von HHG in Argon, wobei Anzeichen einer starken Feldfangung von Elektronen in angeregten Zuständen im HHG-Spektrum entdeckt werden. Die Arbeit zeigt die entscheidende Rolle angeregter Zustände in der HHG auf. Zusätzlich wird die Anwendung synthetischer chiraler Felder erforscht, um Chiralität auf achirale Objekte wie Atome zu übertragen, und es wird eine Verbindung zwischen synthetischen chiralen Feldern und strukturiertem Licht hergestellt., In recent decades table-top laser sources have undergone remarkable development and are now capable of generating tailored ultrashort multicolor laser pulses, enabling the study of electronic dynamics in materials on their natural timescale of the attoseconds. In this thesis work various combinations of electric fields spanning from extreme-ultraviolet (XUV) to near-infrared wavelengths are used to investigate, reconstruct and control complex electron dynamics in atoms and chiral media. The initial chapter of this thesis introduces the fundamental concepts underlying light-matter interaction, including strong field processes which lie at the core of attosecond spectroscopy. The second chapter focuses on the utilization of an XUV pulse combined with a near-infrared pulse to study population transfer to high angular momentum states in helium atoms. By manipulating laser parameters, the study identifies the significant role played by the AC Stark shift of bound states in the observed dynamics. In the third chapter a bicircular electric field is employed to induce HHG in argon. Changing the timedelay between the two frequencies, indications of strong field trapping of electrons in excited states are uncovered within the HHG spectrum, confirming the existence of long-lived trajectories lasting multiple optical cycles. The study conclusively demonstrates the crucial role of excited states in HHG. The fourth chapter explores the application of synthetic chiral fields—whose polarization traces a chiral curve over the optical cycle—to imprint chirality on achiral objects such as atoms, both in the low- and strong-field regime. Moreover, the thesis establishes a connection between synthetic chiral fields and structured light, introducing chiral vortex beams with azimuthally varying handedness.

Wird DNA mit UV-Licht bestrahlt, kommt es zur Bildung von Photoschäden, die zu Zelltod oder Krebs führen können. In dieser Arbeit wird die primäre Elektronentransferreaktion des lichtaktivierten Reparaturprozesses des (6-4)-Schadens in Drosophila melanogaster charakterisiert. Der katalytische Reparaturzyklus wird durch das Flavoprotein (6-4)-Photolyase (PL) realisiert. Der Elektronentransfer (ET) vom Flavin-Adenin-Dinukleotid (FADH⁻) Kofaktor zum Schaden initiiert die molekularen Umlagerungen. Diese Arbeit charakterisiert die primäre ET Reaktion mithilfe von molekulardynamischen Langzeitsimulationen (µs) in Kombination mit Quantenmechanik/Molekularmechanik-Simulationen. Ab initio lokale Coupled-Cluster- und Dichtefunktionaltheorierechnungen wurden angewendet, um die relative Energetik von lokal angeregten und Ladungstransferzuständen des (6-4)-Reparaturkomplexes zu charakterisieren. Es zeigt sich, dass die Reduktion des (6-4)-Schadens durch einen Ladungstransferzustand ermöglicht wird an dem die Adeninstruktur des FADH⁻ -Kofaktors beteiligt ist. Über die Simulationen wird ein mikroskopisches Bild der Reaktionskoordinate der Elektronentransferreaktion im Marcusbild entwickelt. Diese ist nicht vollständig durch parabolische freie Energiekurven beschrieben sondern wird, durch Wechselwirkungen in der aktiven Tasche, ein Multiminima-Reaktionspfad ausgebildet. Hierbei hat die Rotation der Seitenkette der benachbarten, geladenen Aminosäure Lys246 dominanten Einfluss. Dies legt nahe, dass die primäre ET Reaktion der (6-4) Schadensreparatur, einen vom Adenin unterstützten ET Weg von der PL zur 5’ Seite des Schadens nimmt. Dieser Prozess wird durch benachbarte Aminosäuren und einer Stärkung der Wasserstoffbrücken mit Wassermolekülen stabilisiert. Die Ergebnisse dieser Arbeit zeigen, dass ET-Reaktionen in komplexen enzymatischen Systemen nicht im Kontinuumsbild von ET beschrieben werden können, da lokale Wechselwirkungen drastischen Einfluss auf die ET Reaktionen haben., UV-light irradiation of DNA leads to the formation of photolesions that can cause cell death and cancer. This thesis aims at the characterization of the primary electron transfer (ET) reaction in the photoactivated repair process of the (6-4) lesion in Drosophila melanogaster. The catalytic repair cycle is realized by a flavoprotein called photolyase (PL). The ET from the fully reduced flavin-adenine-dinucleotide (FADH⁻) cofactor of the PL to the lesion initiates molecular rearrangements. In this thesis fluctuation properties of the enzyme environment on the excited states are considered by conducting long-time (µs) molecular dynamics simulations combined with extensive quantum mechanical/molecular mechanical simulations. Ab initio local coupled cluster simulations and density functional theory are applied to characterize the relative energetics of locally excited and charge transfer (CT) states in the (6-4) lesion repair complex. Reduction of the (6-4) lesion is found to be enabled by a CT state involving the adenine moiety of the FADH⁻ cofactor. Microscopic characterization of a Marcus-type free energy reaction coordinate reveals that it cannot be fully described by parabolic free energy curves. Specifically, rotation of the side chain of nearby charged amino acid Lys246 imposes a double-well character on the potential energy surface along the reaction coordinate of the ET. For the ET reaction triggering the catalytic (6-4) lesion repair, the findings of this thesis suggest an ET pathway to the 5’ side of the (6-4) lesion mediated by the adenine moiety. The process is stabilized by neighboring amino acids and a strengthening of hydrogen bonds with water molecules. The presented results demonstrate that ET reactions in complex enzymatic systems cannot be described within the continuum ET picture, as local interactions drastically tune the ET reaction.

Im ersten Teil dieser Arbeit wird die zeitliche Korrelation von Photonen untersucht, welche durch parametrischer Fluoreszenz in einem nichtlinearen Medium innerhalb eines Resonators erzeugt werden. Dafür wird eine komplette theoretische Beschreibung hergeleitet, welche die zeitlichen Korrelationen zwischen signal-idler, signal-signal und signal-signal-idler Photonen mittels spektraler Eigenschaften der Photonenquelle beschreibt. Damit lässt sich der Einfluss des Resonators auf die zeitlichen Korrelationen bestimmen. Passende experimentelle Messungen werden präzise durch diese Theorie beschrieben, wodurch diese bestätigt werden konnte. Im zweiten Teil dieser Arbeit wird erstmalig die Austauschphase von Photonen direkt gemessen. Um die Austauschphase in einer direkten Messung zu bestimmen, muss der ursprüngliche Zwei-Photonen-Zustand mit seinem permutierten Zustand interferieren. Für die experimentelle Umsetzung wird ein neues spezielles Interferometer benötigt, welches hier vorgestellt und charakterisiert wird. Mithilfe der durchgeführten Experimente konnten die bosonischen Eigenschaften von Photonen nachgewiesen und eine untere Grenze für eine direkt gemessen Austauschphase festgelegt werden. Der letzte Teil dieser Arbeit untersucht Frequenzkonversion in nichtlinearen Medien. Durch die Verwendung mehrere Kornversionsschritte ist es z.B. möglich die Erzeugung von Rauschphotonen bei bestimmten Zielwellenlänge zu verhindern. Hier wird eine Möglichkeit vorgestellt bei der mehrere Kornversionsschritte innerhalb eines nichtlinearen Kristalls realisiert werden, indem der Kristall lokal verschieden temperiert wird. Die Durchführbarkeit dieser Technik wurde theoretisch untersucht und experimentell bestätigt. Weitere Anwendungsmöglichkeiten werden ausführlich diskutiert., The first part of this thesis investigates the temporal correlation of photons, generated in a spontaneous parametric down-conversion process inside of a nonlinear crystal, which is placed in a resonator to enhance specific emission lines. However, the cavity influences the temporal correlation of the photons, which is crucial for most applications. This thesis derives a complete theory to describe the temporal correlations of signal-idler, signal-signal and signal-signal-idler photons using the spectral properties of the photon source. The derived theoretical description precisely predicts the experimental measurements, which were performed to verify the theory. In the second part the exchange phase of photon is measured directly for the first time. Directly, this can only be verified experimentally by interference between the two-photon state and its permuted form. Here a new interferometer technique is introduced to directly determine the photon exchange phase. The experimental results provide evidence of the bosonic nature of photons and state a lower bound for a directly measured exchange phase of photons. The last part deals with frequency conversion in nonlinear materials. Depending on the wavelengths involved, the conversion processes introduce noise at the target wavelength, which is critical at the single photon level. Then multiple conversion steps are required for a low noise frequency conversion. We present an approach to realize multiple conversion steps with a single nonlinear crystal by applying different local temperatures to that nonlinear crystal. The feasibility of that approach is confirmed experimentally and further possible applications are considered.

Siliziumsensoren werden aufgrund ihrer hohen Strahlenhärte und mechanischen Stabilität in der Hochenergiephysik breit eingesetzt. Während des Herstellungsprozesses werden jedoch einige Defekte auf der Sensoroberfläche erzeugt, was zu komplexen Oberflächeneigenschaften führt. Die großflächigen Siliziumsensoren für das ATLAS Inner Tracker (ITK) Upgrade zeigen eine Sensitivität auf Luftfeuchtigkeit, was dazu führt, dass die Sensoren einen hohen Leckstrom aufweisen und dadurch mitunter nicht mehr als Teilchendetektoren unter einer hohen Spannung in einer Umgebung mit hoher Luftfeuchtigkeit betrieben werden können. Zur Erforschung der Oberflächeneigenschaften und um den Breakdown-Mechanismus zu verstehen, wird die Top Transient Current Technique (Top TCT) eingesetzt, um den Ladungstransportprozess in Siliziumsensoren zu analysieren. Diese Methode verwendet schnelle Laserpulse, die auf einen mikrometergroßen Bereich fokussiert sind, um die Vorderseite des Sensors zu beleuchten und Elektron-Loch-Paare innerhalb der ersten Mikrometer unter der Oberfläche zu erzeugen. Diese Ladungsträger bewegen sich unter dem Einfluss des angelegten elektrischen Feldes, wodurch transiente Ströme an der Elektrode induziert werden. Durch die Analyse dieser transienten Signale, in Abhängigkeit von der Position des laserinjizierten Bereiches und der angelegten Spannung, kann das elektrische Feld in der Nähe der Oberfläche qualitativ abgeschätzt werden. In dieser Arbeit werden sowohl Simulation als auch Messung unter Verwendung der Top TCT-Methode an einer planaren Diode durchgeführt. Die Simulation erfolgt mithilfe der Software Allpix Squared, einem Monte-Carlo-Simulationsframework, das speziell für Halbleiterdetektoren entwickelt wurde. Die effektive Dotierstoffkonzentration, die Vollverarmungsspannung und die aktive Dicke einer planaren Silizium n-in-p Diode werden mit der Top TCT-Methode gemessen. Die Übertragungsfunktion des externen Stromkreises wird durch Fourier-Transformationsanalyse so, Silicon sensors are widely used in high-energy physics due to their high radiation hardness and mechanical stability. However, during the fabrication process, several defects are introduced to the sensor surface, resulting in complex surface properties. The large-area silicon sensors for the ATLAS Inner Tracker (ITK) Upgrade show signs of early surface breakdown at high humidity. This results in the sensors experiencing a high leakage current and are not inoperable as particle detectors when biased in a high-humidity environment. To investigate the surface properties and understand the breakdown mechanism, the Top Transient Current Technique (Top TCT) is used to study the charge transport process in silicon sensors. This method utilizes fast laser pulses, focused to a micrometer-sized spot, to illuminate the front side of the sensor, generating electron-hole pairs within the first several micrometers from the surface. These charge carriers then drift under the influence of the applied electric field, inducing transient currents on the electrode. By analyzing these transient signals as a function of the laser-injected position and the applied bias voltage, the distribution of the surface electric field can be qualitatively estimated. In this work, both simulation and measurement using the Top TCT method on a planar diode are performed. The simulation is conducted using the Allpix Squared software, a Monte Carlo simulation framework specially developed for semiconductor detectors. The effective doping concentration, full-depletion voltage, and active thickness of a planar silicon n-in-p diode are measured using the Top TCT method. The transfer function of the read-out electric circuit is extracted through Fourier transform analysis of both the simulated and measured data. A new parameter ”surface reflectivity” is implemented and modified in Allpix Squared to simulate the charge transport at the silicon-silicon dioxide interface, where a field pushing the electrons tow

The article processing charge was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 491192747 and the Open Access Publication Fund of Humboldt-Universität zu Berlin., Social semiotic discussions about the role played by representations in effective teaching and learning in areas such as physics have led to theoretical proposals that have a strong common thread: in order to acquire an appropriate understanding of a particular object of learning, access to the disciplinary relevance aspects in the representations used calls for the attainment of representational competence across a particular critical constellation of systematically used semiotic resources (which are referred to as modes, see more on this later). However, an affirming empirical investigation into the relationship between a particular object of learning and different representational formulations, particularly with large numbers of students, is missing in the literature, especially in the context of university-level physics education. To start to address, this research shortfall the positioning for this article is that such studies need to embrace the complexities of student thinking and application of knowledge. To achieve this, both factor and network analyses were used. Even though both approaches are grounded in different frameworks, for the task at hand, both approaches are useful for analyzing clustering dynamics within the responses of a large number of participants. Both also facilitate an exploration of how such clusters may relate to the semiotic resource formulation of a representation. The data were obtained from a questionnaire given to 1368 students drawn from 12 universities across 7 countries. The questionnaire deals with the refraction of light in introductory-level physics and involves asking students to give their best prediction of the relative visual positioning of images and objects in different semiotically constituted situations. The results of both approaches revealed no one-to-one relationship between a particular representational formulation and a particular cluster of student responses. The factor analysis used correct answer responses to, Peer Reviewed

Colonies of bacteria endowed with a pili-based self-propulsion machinery are ideal models for investigating the structure and dynamics of active many-particle systems. We study Neisseria gonorrhoeae colonies with a molecular-dynamics-based approach. A generic, adaptable simulation method for particle systems with fluctuating bond-like interactions is devised. In a first study, the simulations are employed to investigate growth of bacterial colonies and the dependence of the colony structure on cell-cell interactions. In colonies, pilus retraction enhances local ordering. For colonies consisting of different types of cells, the simulations show a segregation depending on the pili-mediated interactions among different cells. These results agree with experimental observations. Next, we quantify the power-spectral density of colony-shape fluctuations in silico. Simulations predict a strong violation of the equilibrium fluctuation-response relation. Furthermore, we show that active force generation enables colonies to spread on surfaces and to invade narrow channels. The methodology can serve as a foundation for future studies of active many-particle systems at boundaries with complex shape. Bacterial colonies can attach and wet on surfaces like liquid droplets. Little is known about what factors affect the wetting of bacterial colonies. In a second study, we combine experimental data with our particle-based simulations and analytical calculations to show that azithromycin treatment enhances the wettability of Neisseria gonorrhoeae colonies. We show that the steady-state contact angle is not only determined by parameters that determine an equilibrium state, but also depends on dynamical quantities like the friction constant. Thus, surface-wetting of Neisseria gonorrhoeae colonies is a genuine non-equilibrium process. The thickness of the diffuse interface of the colonies is non-negligible compared to the colony radius, which gives rise to a finite Tolman length and a con

The protoplanetary disks around YSOs have a key role in the still unclear processes of planet formation and evolution. However, their picture is not yet complete, especially with regards to their innermost regions, observed through long-baseline IR interferometry, required to probe sub-au scales. Particularly interesting are the YSOs belonging to the Herbig stars sub-group. With a stellar mass set to range between 2 and 12 solar masses, they are thought to be the bridge between the relatively well understood low mass pre-main-sequence stars and the still obscure high mass ones. In this work I study three different Herbig stars, each one of them being a benchmark for various open-ended questions on young stellar objects evolution and on the physical processes happening in their innermost circumstellar regions. The first is HD141569, a well-known Herbig star characterized by a transitional disk. GRAVITY detected a very faint dust emission in the first au of the system, previously thought to be dust-depleted. The system, despite his old age, shows a Br-gamma-line emission, for which the GRAVITY spectrum and differential phases suggest the emitting gas to lie in a Keplerian disk around the central star. Through the study of the second system, HD98922, a unique variability investigation of its innermost gas and dust material is presented. I suggest a way to bypass poor (u,v)-plane coverage and to assess variability through interferometric data geometrical modeling. The modeling suggests an orbiting, crescent, dusty feature, hinting to a dust-trap scenario at mas scale in the first au of the HD98922 circumstellar environment. A strongly time-variable Br-gamma-line emission is also observed, which follows at first order the orbital motion of the dusty feature. Lastly, the quadruple Herbig stars system HD52721 is studied and tested for interferometric binarity in au scales. A new companion is detected, as well as a complex and strongly time-variable Br-gamma-line emission.

In econophysics, the intersection of statistical physics and economics offers a unique viewpoint for deciphering complex economic systems. This thesis uses a complex systems framework to study the intricate dynamics of supply networks and energy systems. The research initially investigates the creation of supply networks, with economies of scale emerging as a critical influencer. The research highlights the process of globalization using an abstract theoretical model, demonstrating the shift from localized to centralized production. When the model accounts for differences in agent preferences, it reveals three unique trade regimes: local, centralized, and diversified production. The results emphasize the significant impact of transportation costs, preference diversity, and economic scale effects on global trade patterns. The following section of the thesis examines the concept of demand response in electric power systems, focusing on the advantages of load shifting at the individual household level through an agent-based model. However, the coordinated operation of these systems based on real-time pricing may result in synchronization, potentially creating grid stability issues. Additionally, the thesis presents an extensive statistical study of electricity price time series in the European electricity exchange market. The research identifies time scales intrinsic to price dynamics by addressing non-stationarities and fitting data to appropriate models. A significant finding is a strong correlation between weather conditions and electricity price dynamics, emphasizing the importance of considering external factors in agent-based models. This thesis aims to objectively understand collective behaviors within econo-physical models of supply networks and energy systems. The agent-based models presented establish a basis for future research, highlighting the potential integration of advanced tools such as machine learning. The research yields significant findings and ins

Characterizing the set of correlations that can arise from performing measurements in a quantum description of Nature is a relevant, but challenging task. Such a characterization, known as the quantum causal compatibility problem, provides us with insights in the advantages of quantum theory over a classical theory, but can also show its limitations. This problem becomes particularly challenging when the quantum states and measurements are required to be compatible with a given causal structure. A causal structure dictates the causal dependencies of the parties and systems involved in the experiment. One can think of the Bell scenario as one of the simplest causal structures, in which two spatially separated parties, Alice and Bob, are assumed to perform a measurement on a shared source. In more general causal structures we might have more parties, and more sources that are independent of each other. Recently, a systematic way of analyzing the correlations in classical and quantum causal structures was proposed in the form of the inflation technique. In the inflation technique the causal dependencies, which are difficult to encode algorithmically, are relaxed to easy-to-encode symmetry constraints on a larger number of parties. For the classical case, this provides a converging hierarchy of linear programs for the causal compatibility problem. For the quantum case, it instead yields a hierarchy of increasingly restrictive semidefinite programming relaxations. It is, however, unknown whether this hierarchy is also complete. One of the main results of this thesis is to show that a modified version of the quantum inflation technique is convergent for the quantum causal compatibility problem. This modified hierarchy introduces an additional parameter, r, that restricts the Schmidt rank of the observables. For each value of r we provide a hierarchy of compatibility tests that is complete in the sense that it will detect, at some finite level, any probability distribution

We investigate the applicability of the well-known multilevel Monte Carlo (MLMC) method to the class of density-driven flow problems, in particular the problem of salinisation of coastal aquifers. As a test case, we solve the uncertain Henry saltwater intrusion problem. Unknown porosity, permeability and recharge parameters are modelled by using random fields. The classical deterministic Henry problem is non-linear and time-dependent, and can easily take several hours of computing time. Uncertain settings require the solution of multiple realisations of the deterministic problem, and the total computational cost increases drastically. Instead of computing of hundreds random realisations, typically the mean value and the variance are computed. The standard methods such as the Monte Carlo or surrogate-based methods are a good choice, but they compute all stochastic realisations on the same, often, very fine mesh. They also do not balance the stochastic and discretisation errors. These facts motivated us to apply the MLMC method. We demonstrate that by solving the Henry problem on multi-level spatial and temporal meshes, the MLMC method reduces the overall computational and storage costs. To reduce the computing cost further, parallelization is performed in both physical and stochastic spaces. To solve each deterministic scenario, we run the parallel multigrid solver ug4 in a black-box fashion.

This thesis contains three theoretical works about certain aspects of the interplay of electronic correlations and topology in the Hubbard model. In the first part of this thesis, the applicability of elementary band representations (EBRs) to diagnose interacting topological phases, that are protected by spatial symmetries and time-reversal-symmetry, in terms of their single-particle Matsubara Green’s functions is investigated. EBRs for the Matsubara Green’s function in the zero-temperature limit can be defined via the topological Hamiltonian. It is found that the Green’s function EBR classification can only change by (i) a gap closing in the spectral function at zero frequency, (ii) the Green’s function becoming singular i.e. having a zero eigenvalue at zero frequency or (iii) the Green’s function breaking a protecting symmetry. As an example, the use of the EBRs for Matsubara Green’s functions is demonstrated on the Su-Schriefer-Heeger model with exact diagonalization. In the second part the Two-Particle Self-Consistent approach (TPSC) is extended to include spin-orbit coupling (SOC). Time-reversal symmetry, that is preserved in the presence of SOC, is used to derive new TPSC self-consistency equations including SOC. SOC breaks spin rotation symmetry which leads to a coupling of spin and charge channel. The local and constant TPSC vertex then consists of three spin vertices and one charge vertex. As a test case to study the interplay of Hubbard interaction and SOC, the Kane-Mele-Hubbard model is studied. The antiferromagnetic spin fluctuations are the leading instability which confirms that the Kane-Mele-Hubbard model is an XY antiferromagnet at zero temperature. Mixed spin-charge fluctuations are found to be small. Moreover, it is found that the transversal spin vertices are more strongly renormalized than the longitudinal spin vertex, SOC leads to a decrease of antiferromagnetic spin fluctuations and the self-energy shows dispersion and sharp features in momentu

Controlling and understanding electron correlations in quantum matter is one of the most challenging tasks in materials engineering. In the past years a plethora of new puzzling correlated states have been found by carefully stacking and twisting two-dimensional van der Waals materials of different kind. Unique to these stacked structures is the emergence of correlated phases not foreseeable from the single layers alone. In Ta-dichalcogenide heterostructures made of a good metallic “1H”- and a Mott insulating “1T”-layer, recent reports have evidenced a cross-breed itinerant and localized nature of the electronic excitations, similar to what is typically found in heavy fermion systems. Here, we put forward a new interpretation based on first-principles calculations which indicates a sizeable charge transfer of electrons (0.4-0.6 e) from 1T to 1H layers at an elevated interlayer distance. We accurately quantify the strength of the interlayer hybridization which allows us to unambiguously determine that the system is much closer to a doped Mott insulator than to a heavy fermion scenario. Ta-based heterolayers provide therefore a new ground for quantum-materials engineering in the regime of heavily doped Mott insulators hybridized with metallic states at a van der Waals distance.

Although iron-based catalysts are regarded as a promising alternative to precious metal catalysts, their precise electronic structures during catalysis still pose challenges for computational descriptions. A particularly urgent question is the influence of the environment on the electronic structure, and how to describe this properly with computational methods. Here, we study an iron porphyrin chloride complex adsorbed on a graphene sheet using density functional theory calculations to detail how much the electronic structure is influenced by the presence of a graphene layer. Our results indicate that weak interactions due to van der Waals forces dominate between the porphyrin complex and graphene, and only a small amount of charge is transferred between the two entities. Furthermore, the interplay of the ligand field environment, strong p − d hybridization, and correlation effects within the complex are strongly involved in determining the spin state of the iron ion. By bridging molecular chemistry and solid state physics, this study provides first steps towards a joint analysis of the properties of iron-based catalysts from first principles.

We prove that the projectivized strata of differentials are not contained in pointed Brill-Noether divisors, with only a few exceptions. For a generic element in a stratum of differentials, we show that many of the associated pointed Brill-Noether loci are of expected dimension. We use our results to study the Auel-Haburcak Conjecture: We obtain new non-containments between maximal Brill-Noether loci in Mg. Our results regarding quadratic differentials imply that the quadratic strata in genus 6 are uniruled.

Das Experiment ALICE (A Large Ion Collider Experiment) am CERN (Conseil Européen pour la Recherche Nucléaire) LHC (Large Hadron Collider) fokussiert sich auf die Untersuchung stark wechselwirkender Materie unter extremen Bedingungen. Solche Bedingungen existierten wenige Mikrosekunden nach dem Urknall, als die Temperaturen so hoch waren, dass Partonen (Quarks und Gluonen) nicht zu farbneutralen Hadronen gebunden waren. In solch einem Quark-Gluon-Plasma können sich die Partonen frei bewegen, wobei sie allerdings mit anderen Partonen aus dem Medium stark wechselwirken. Am LHC werden Bleikerne auf ultra-relativistische Energien von bis zu 2.68 TeV beschleunigt und zur Kollision gebracht, wobei für weniger als 10 fm/c ein QGP entsteht, das schnell expandiert. Die Partonen hadronisieren, wenn das QGP sich auf Temperaturen von weniger als der Phasenübergangstemperatur von ≈155MeV abkühlt. Die finalen Teilchen- und Impulsverteilungen werden werden vom ALICE Detektor gemessen und geben Aufschluss auf elementare Prozesse im QGP. Die TPC (Time Projection Chamber ) ist eines der wichtigsten Detektorsysteme von ALICE. Sie trägt maßgeblich zur Rekonstruktion von Teilchenspuren und zur Identifikation der Teilchensorten bei mittleren Rapiditäten bei. Die TPC ist eine große zylindrische Spurendriftkammer und besteht aus einem 88mˆ3 großen Gasvolumen, das von der zentralen Hochspannungselektrode in zwei Seiten geteilt wird. Durchquert ein Teilchen das Gasvolumen, ionisiert es entlang seiner Spur eine spezifische Menge von Gasatomen. Die Ionisationselektronen driften entlang des extrem homogenen elektrischen Feldes zu den Auslesekammern an den Endkappen auf beiden Seiten der TPC. Die Messung der Position und der Menge der Ionisationselektronen erlaubt die Rekonstruktion der Teilchenspur sowie, in Kombination mit der Impulsmessungen über die Krümmung der Teilchenspur im Magnetfeld, die Bestimmung der Teilchensorte über den spezifischen Energieverlust pro Wegstrecke im Gas. Das Gasvolu

The ALICE Collaboration reports a differential measurement of inclusive jet suppression using pp and Pb−Pb collision data at a center-of-mass energy per nucleon-nucleon collision sNN−−−√=5.02 TeV. Charged-particle jets are reconstructed using the anti-kT algorithm with resolution parameters R= 0.2, 0.3, 0.4, 0.5, and 0.6 in pp collisions and R= 0.2, 0.4, 0.6 in central (0−10%), semi-central (30−50%), and peripheral (60−80%) Pb−Pb collisions. A novel approach based on machine learning is employed to mitigate the influence of jet background. This enables measurements of inclusive jet suppression in new regions of phase space, including down to the lowest jet pT≥40 GeV/c at R=0.6 in central Pb−Pb collisions. This is an important step for discriminating different models of jet quenching in the quark-gluon plasma. The transverse momentum spectra, nuclear modification factors, derived cross section, and nuclear modification factor ratios for different jet resolution parameters of charged-particle jets are presented and compared to model predictions. A mild dependence of the nuclear modification factor ratios on collision centrality and resolution parameter is observed. The results are compared to a variety of jet-quenching models with varying levels of agreement.

By combining two unique facilities at the Gesellschaft fuer Schwerionenforschung (GSI), the Fragment Separator (FRS) and the Experimental Storage Ring (ESR), the first direct measurement of a proton capture reaction of stored radioactive isotopes was accomplished. The combination of well-defined ion energy, an ultra-thin internal gas target, and the ability to adjust the beam energy in the storage ring enables precise, energy-differentiated measurements of the (p,gamma) cross sections. The new setup provides a sensitive method for measuring (p,gamma) reactions relevant for nucleosynthesis processes in supernovae, which are among the most violent explosions in the universe and are not yet well understood. The cross sections of the 118Te(p,gamma) and 124Xe(p,gamma) reactions were measured at energies of astrophysical interest. The heavy ions were stored with energies of 6 MeV/nucleon and 7 MeV/nucleon and interacted with a hydrogen gas-jet target. The produced proton-capture products were detected with a double-sided silicon strip detector. The radiative recombination process of the fully stripped ions and electrons from the hydrogen target was used as a luminosity monitor. Additionally, post-processing nucleosynthesis simulations within the NuGrid [1] research platform have been performed. The impact of the new experimental results on the p-process nucleosynthesis around 124Xe and 118Te in a core-collapse supernova was investigated. The successful measurement of the proton capture cross sections of radioactive isotopes rises the motivation to proceed with experiments in lower energy regions. [1] M. Pignatari and F. Herwig, “The nugrid research platform: A comprehensive simulation approach for nuclear astrophysics,” Nuclear Physics News, vol. 22, no. 4, pp. 18–23, 2012., Durch die Kombination zweier außergewöhnlicher Anlagen der Gesellschaft für Schwerionenforschung (GSI), dem Fragmentseparator (FRS) und dem Experimentier-Speicherring (ESR), wurden die ersten direkten Messungen von Protoneneinfangsreaktionen an gespeicherten radioaktiven Isotopen durchgeführt. Die Kombination aus genau bekannter Ionenenergie, einem sehr dünnen Gastarget und der Möglichkeit, die Energie des Strahls im Ring zu regulieren, ermöglicht präzise, energiedifferenzierte Messungen der (p,) Wirkungsquerschnitte. Mit dem neuen Aufbau steht eine sensitive Methode zur Messung von (p,) Reaktionen zur Verfügung, die für Nukleosyntheseprozesse in Supernovae relevant sind, welche zu den gewaltigsten Explosionen im Universum gehören und noch nicht vollständig verstanden sind. Im Rahmen dieser Arbeit wurden die Wirkungsquerschnitte der Reaktionen 118Te(p,) und 124Xe(p,) bei Energien von astrophysikalischem Interesse gemessen. Die schweren Ionen wurden mit Energien von 6 MeV/Nukleon und 7 MeV/Nukleon gespeichert und wechselwirkten mit einem Wasserstoff-Gasjet-Target. Die beim Protoneneinfang entstandenen Ionen wurden mit einem doppelseitigen Siliziumstreifendetektor nachgewiesen. Die nach der Rekombination der ionisierten Atome mit den Elektronen aus dem Wasserstofftarget ausgesendete Strahlung, wurde als Luminositätsmonitor verwendet [1]. Diese Messungen folgen einem im Jahr 2016 durchgeführten Proof-of-Principle-Experiment zur Validierung der Methode an dem stabilen Isotop 124Xe [2]. Zusätzlich wurden post-processing Nukleosynthese Studien, innerhalb der Nu-Grid [3] Plattform durchgeführt. Der Einfluss der neuen experimentellen Daten auf die Nukleosynthese von 118Te und 124Xe in Kernkollaps Supernovae wurde untersucht. Die erfolgreiche Messung von Protoneneinfangswirkungsquerschnitten an radioaktiven Isotopen motiviert weitere Experimente in niedrigeren Energiebereichen durchzuführen.

In this thesis, the early time dynamics in a heavy ion collision of Pb-Nuclei at LHC center-of-mass energies of 5 TeV is studied. Right after the collision the system is out-of-equilibrium and essentially gluon dominated, with their density saturating at a specific momentum scale Q_s. Based on a separation of scales for the soft and hard gluonic degrees of freedom, the initial state is given from an effective model, known as the Color Glass Condensate. Within this model, the soft gluons behave classical to leading order, making it possible to study their dynamics in gauge invariant fashion on a three dimensional lattice, solving Hamiltonian field equations of motion, keeping real time. Quark-Antiquark pairs are produced in the gluonic medium, known as the Glasma and manifest themselves as a source of quantum fluctuations. They enter the dynamics of the gluons as a current, making the system semi-classical. In lattice simulations, the non-equilibrium system is tested for pressure isotropization, which is a necessary ingredient to reach a local thermal equilibrium (LTE), making a hydrodynamical description at a later stage possible. In addition, the occupation of energy modes is studied with its implications on thermalization and classicality.

In this work I investigate two different systems - spin systems and charge-density-waves. The same theoretical method is used to investigate both types of system. My investigations are motivated by experimental investigations and the goal is to describe the experimental results theoretically. For this purpose I formulate kinetic equations starting from the microscopical dynamics of the systems. First of all, a method is formulated to derive the kinetic equations diagrammatically. Within this method an expansion in equal-time connected correlation functions is carried out. The generating functional of connected correlations is employed to derive the method. The first system to be investigated is a thin stripe of the magnetic insulator yttrium-iron-garnet (YIG). Magnons are pumped parametrically with an external microwave field. The motivation of my theoretical investigations is to explain the experimental observations. In a small parameter range close to the confluence field strength where confluence processes of two parametrically pumped magnons with the same wave vector becomes kinematically possible the efficiency of the pumping is reduced or enhanced depending on the pumping field strength. Because it is expected that that confluence and splitting processes of magnons are essential for the experimental observations I go beyond the kinetic theories that are conventionally applied in the context of parametric excitations in YIG and investigate the influence of cubic vertices on the parametric instability of magnons in YIG. Furthermore, the influence of phonons is investigated. Usually in the literature these are taken into account as heat bath. Here, I want to explain experiments where an accumulation of magnetoelastic bosons - magnon-phonon-quasi-particles - has been observed. I employ the method of kinetic equations to investigate this phenomenon theoretically. The kinetic theory is able to reproduce the experimental observations and it is shown that the accumula, In dieser Arbeit werden zwei verschiedene Systeme untersucht - Spinsysteme, die Spinwellen bzw. deren elementare Anregungen, Magnonen, aufweisen, und elektronische Systeme mit Elektron-Phononkopplung, in dem Ladungsdichtewellen beobachtet werden können. Die Untersuchungen von beiden Systemen sind jeweils durch experimentelle Beobachtungen motiviert. Das Ziel dieser Untersuchungen ist es, diese Beobachtungen theoretisch zu erklären. Dazu gehe ich von der mikroskopischen Dynamik des Systems aus, die mithilfe von kinetischen Gleichungen beschrieben wird. Zunächst wird eine Methode eingeführt, mit der die kinetischen Gleichungen diagrammatisch hergeleitet werden können. Innerhalb dieser Methode wird eine Entwicklung in einzeitigen, verbundenen Korrelationsfunktionen durchgeführt und es wird das erzeugende Funktional der verbundenen Korrelationsfunktionen zur Herleitung der Methode verwendet. Das erste System, das untersucht werden soll, ist ein dünner Streifen bestehend aus dem magnetischen Isolator Yttrium-Eisen-Granat (YIG). Die Motivation liegt darin, ein Experiment zu erklären, in dem Magnonen in YIG parametrisch gepumpt wurden. Es wurde beobachtet, dass in einem kleinen Parameterbereich rund um die Konfluenzfeldstärke, bei der Konfluenzprozesse von zwei parametrisch gepumpten Magnonen mit gleichem Wellenvektor kinematisch möglich werden, die Effizienz des Pumpens abhängig von der Pumpstärke kleiner order größer wird. Da anzunehmen ist, dass Konfluenz und Splittingprozesse für den beobachteten Effekt relevant sind, gehe ich über die konventionellen kinetischen Theorien hinaus, die im Kontext vom YIG üblicherweise verwendet werden, und untersuche den Einfluss der kubischen Vertices auf die parametrische Stabilität von Magnonen in YIG. Anschließend wird ebenfalls der Einfluss der Phononen untersucht. Diese werden üblich erweise lediglich als Wärmebad betrachtet. Hier geht es allerdings darum, experimentelle Beobachtungen zu erklären, bei denen eine Akkumulation von ma