Theoretical and experimental studies on intense laser atom interaction have drawn many interests over the past few decades. In this thesis, we consider strong-field tunnel ionization to explore two different problems dealing with the ionized-electron dynamics in the presence of an infrared, high-intensity, elliptically-polarized laser pulse. In the first part, we discover the electron dynamics from a static potential, this describes the complicated field-driven dynamics by a simple time-independent problem. In the second part, we set up an analytical expression for the attoclock offset angle. We use the time-dependent Kramers-Henneberger (KH) potential, and show how some approximations within the KH potential lead to the static potential and the analytical offset angle. We elucidate good agreement of our theory with the numerical results obtained from classical equations of motion. Finally, the comparison with the available experimental data has led to an interestingly new tunnel exit-radius different from the conventional models.

As of June 2020, the first all-sky X-ray survey with the eROSITA instrument aboard the spacecraft Spektr-RG has been completed. A high percentage of the 1.1 million objects included in the survey are expected to be active galactic nuclei (AGN). Such an extensive catalogue of X-ray sources offers a unique opportunity for large scale observations of distinct classes of X-ray emitters. This report explores methods of refining the catalogue to include only candidates for lensed AGN. Of the differing types of AGN known, quasi-stellar objects, or QSOs, are some of the most luminous, meaning they are well-suited for observation over large distances. This is particularly befitting for observation of gravitationally lensed objects as, for lensing effects to take place, large distances are required over which more faint objects would not be able to be viewed. An indication of strong gravitational lensing is several images of the same object seen in close proximity on the sky. In order to reduce the data to more likely candidates, counterparts within a given radius are found in the second data release from Gaia; a survey in the optical with higher resolution than eROSITA. An algorithm is produced which removes most likely stellar Gaia sources using their X-ray to optical flux ratios and astrometry parameters. The Gaia sources which have no neighbours within another given radius are then also removed, leaving a catalogue of potential multiply lensed QSOs. This automated script was then applied to an eROSITA catalogue and the results compared with known lenses. The remaining sources were also checked visually using Pan-STARRS optical survey data. The results seem to be promising, although a great deal further refinement is needed through visual inspection to find the most promising candidates for lensed QSOs. / <p>Written under the joint supervision of Georg Lamer at the Leibniz Institute for Astrophysics in Potsdam. The presentation was held online at the Institute due to the COVID-19 pandemic.</p>

Cette thèse est consacrée à l'étude des propriétés de convergence forte du schéma de Ninomiya et Victoir. Les auteurs de ce schéma proposent d'approcher la solution d'une équation différentielle stochastique (EDS), notée $X$, en résolvant $d+1$ équations différentielles ordinaires (EDOs) sur chaque pas de temps, où $d$ est la dimension du mouvement brownien. Le but de cette étude est d'analyser l'utilisation de ce schéma dans une méthode de Monte-Carlo multi-pas. En effet, la complexité optimale de cette méthode est dirigée par l'ordre de convergence vers $0$ de la variance entre les schémas utilisés sur la grille grossière et sur la grille fine. Cet ordre de convergence est lui-même lié à l'ordre de convergence fort entre les deux schémas. Nous montrons alors dans le chapitre $2$, que l'ordre fort du schéma de Ninomiya-Victoir, noté $X^{NV,eta}$ et de pas de temps $T/N$, est $1/2$. Récemment, Giles et Szpruch ont proposé un estimateur Monte-Carlo multi-pas réalisant une complexité $Oleft(epsilon^{-2}right)$ à l'aide d'un schéma de Milstein modifié. Dans le même esprit, nous proposons un schéma de Ninomiya-Victoir modifié qui peut-être couplé à l'ordre fort $1$ avec le schéma de Giles et Szpruch au dernier niveau d'une méthode de Monte-Carlo multi-pas. Cette idée est inspirée de Debrabant et Rossler. Ces auteurs suggèrent d'utiliser un schéma d'ordre faible élevé au niveau de discrétisation le plus fin. Puisque le nombre optimal de niveaux de discrétisation d'une méthode de Monte-Carlo multi-pas est dirigé par l'erreur faible du schéma utilisé sur la grille fine du dernier niveau de discrétisation, cette technique permet d'accélérer la convergence de la méthode Monte-Carlo multi-pas en obtenant une approximation d'ordre faible élevé. L'utilisation du couplage à l'ordre $1$ avec le schéma de Giles-Szpruch nous permet ainsi de garder un estimateur Monte-Carlo multi-pas réalisant une complexité optimale $Oleft( epsilon^{-2} right)$ tout en profitant de l'erreur faible d'ordre $2$ du schéma de Ninomiya-Victoir. Dans le troisième chapitre, nous nous sommes intéressés à l'erreur renormalisée définie par $sqrt{N}left(X - X^{NV,eta}right)$. Nous montrons la convergence en loi stable vers la solution d'une EDS affine, dont le terme source est formé des crochets de Lie entre les champs de vecteurs browniens. Ainsi, lorsqu'au moins deux champs de vecteurs browniens ne commutent pas, la limite n'est pas triviale. Ce qui assure que l'ordre fort $1/2$ est optimal. D'autre part, ce résultat peut être vu comme une première étape en vue de prouver un théorème de la limite centrale pour les estimateurs Monte-Carlo multi-pas. Pour cela, il faut analyser l'erreur en loi stable du schéma entre deux niveaux de discrétisation successifs. Ben Alaya et Kebaier ont prouvé un tel résultat pour le schéma d'Euler. Lorsque les champs de vecteurs browniens commutent, le processus limite est nul. Nous montrons que dans ce cas précis, que l'ordre fort est $1$. Dans le chapitre 4, nous étudions la convergence en loi stable de l'erreur renormalisée $Nleft(X - X^{NV}right)$ où $X^{NV}$ est le schéma de Ninomiya-Victoir lorsque les champs de vecteurs browniens commutent. Nous démontrons la convergence du processus d'erreur renormalisé vers la solution d'une EDS affine. Lorsque le champ de vecteurs dritf ne commute pas avec au moins un des champs de vecteurs browniens, la vitesse de convergence forte obtenue précédemment est optimale / This thesis is dedicated to the study of the strong convergence properties of the Ninomiya-Victoir scheme, which is based on the resolution of $d+1$ ordinary differential equations (ODEs) at each time step, to approximate the solution to a stochastic differential equation (SDE), where $d$ is the dimension of the Brownian. This study is aimed at analysing the use of this scheme in a multilevel Monte Carlo estimator. Indeed, the optimal complexity of this method is driven by the order of convergence to zero of the variance between the two schemes used on the coarse and fine grids at each level, which is related to the strong convergence order between the two schemes. In the second chapter, we prove strong convergence with order $1/2$ of the Ninomiya-Victoir scheme $X^{NV,eta}$, with time step $T/N$, to the solution $X$ of the limiting SDE. Recently, Giles and Szpruch proposed a modified Milstein scheme and its antithetic version, based on the swapping of each successive pair of Brownian increments in the scheme, permitting to construct a multilevel Monte Carlo estimator achieving the optimal complexity $Oleft(epsilon^{-2}right)$ for the precision $epsilon$, as in a simple Monte Carlo method with independent and identically distributed unbiased random variables. In the same spirit, we propose a modified Ninomiya-Victoir scheme, which may be strongly coupled with order $1$ to the Giles-Szpruch scheme at the finest level of a multilevel Monte Carlo estimator. This idea is inspired by Debrabant and R"ossler who suggest to use a scheme with high order of weak convergence on the finest grid at the finest level of the multilevel Monte Carlo method. As the optimal number of discretization levels is related to the weak order of the scheme used in the finest grid at the finest level, Debrabant and R"ossler manage to reduce the computational time, by decreasing the number of discretization levels. The coupling with the Giles-Szpruch scheme allows us to combine both ideas. By this way, we preserve the optimal complexity $Oleft(epsilon^{-2}right)$ and we reduce the computational time, since the Ninomiya-Victoir scheme is known to exhibit weak convergence with order 2. In the third chapter, we check that the normalized error defined by $sqrt{N}left(X - X^{NV,eta}right)$ converges to an affine SDE with source terms involving the Lie brackets between the Brownian vector fields. This result ensures that the strong convergence rate is actually $1/2$ when at least two Brownian vector fields do not commute. To link this result to the multilevel Monte Carlo estimator, it can be seen as a first step to adapt to the Ninomiya-Victoir scheme the central limit theorem of Lindeberg Feller type, derived recently by Ben Alaya and Kebaier for the multilevel Monte Carlo estimator based on the Euler scheme. When the Brownian vector fields commute, the limit vanishes. We then prove strong convergence with order $1$ in this case. The fourth chapter deals with the convergence of the normalized error process $Nleft(X - X^{NV}right)$, where $X^{NV}$ is the Ninomiya-Victoir in the commutative case. We prove its stable convergence in law to an affine SDE with source terms involving the Lie brackets between the Brownian vector fields and the drift vector field. This result ensures that the strong convergence rate is actually $1$ when the Brownian vector fields commute, but at least one of them does not commute with the Stratonovich drift vector field

Dans une première partie, nous étudions la cohérence dans les systèmes transactionnels, en nous concentrant sur le problème de réconcilier la scalabilité avec des garanties transactionnelles fortes. Nous identifions quatre propriétés critiques pour la scalabilité. Nous montrons qu’aucun des critères de cohérence forte existants n’assurent l’ensemble de ces propriétés. Nous définissons un nouveau critère, appelé Non-Monotonic Snapshot Isolation ou NMSI, qui est le premier à être compatible avec les quatre propriétés à la fois. Nous présentons aussi une mise en œuvre de NMSI, appelée Jessy, que nous comparons expérimentalement à plusieurs critères connus. Une autre contribution est un canevas permettant de comparer de façon non biaisée différents protocoles. Elle se base sur la constatation qu’une large classe de protocoles transactionnels distribués est basée sur une même structure, Deferred Update Replication(DUR). Les protocoles de cette classe ne diffèrent que par les comportements spécifiques d’un petit nombre de fonctions génériques. Nous présentons donc un canevas générique pour les protocoles DUR.La seconde partie de la thèse a pour sujet la cohérence dans les systèmes de stockage non transactionnels. C’est ainsi que nous décrivons Tuba, un stockage clef-valeur qui choisit dynamiquement ses répliques selon un objectif de niveau de cohérence fixé par l’application. Ce système reconfigure automatiquement son ensemble de répliques, tout en respectant les objectifs de cohérence fixés par l’application, afin de s’adapter aux changements dans la localisation des clients ou dans le débit des requête. / In the first part, we study consistency in a transactional systems, and focus on reconciling scalability with strong transactional guarantees. We identify four scalability properties, and show that none of the strong consistency criteria ensure all four. We define a new scalable consistency criterion called Non-Monotonic Snapshot Isolation (NMSI), while is the first that is compatible with all four properties. We also present a practical implementation of NMSI, called Jessy, which we compare experimentally against a number of well-known criteria. We also introduce a framework for performing fair comparison among different transactional protocols. Our insight is that a large family of distributed transactional protocols have a common structure, called Deferred Update Replication (DUR). Protocols of the DUR family differ only in behaviors of few generic functions. We present a generic DUR framework, called G-DUR. We implement and compare several transactional protocols using the G-DUR framework.In the second part, we focus on ensuring consistency in non-transactional data stores. We introduce Tuba, a replicated key-value store that dynamically selects replicas in order to maximize the utility delivered to read operations according to a desired consistency defined by the application. In addition, unlike current systems, it automatically reconfigures its set of replicas while respecting application-defined constraints so that it adapts to changes in clients’ locations or request rates. Compared with a system that is statically configured, our evaluation shows that Tuba increases the reads that return strongly consistent data by 63%.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18801号 / 理博第4059号 / 新制||理||1584(附属図書館) / 31752 / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 岩田 知孝, 教授 平原 和朗, 准教授 久家 慶子 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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Vägtrafik skapar flera negativa konsekvenser för miljön men även för människors hälsa. Kommuner ansvarar för lokal infrastruktur och är därför en betydande del i arbetet med hållbar stadsutveckling. Studien undersökte hur politiker och tjänstemän i Sveriges medelstora kommuner arbetar för att bilen ska bli mindre attraktiv och för att öka hållbar mobilitet. Undersökningen utgick från Sveriges miljömål samt den strategi som innefattar nya etappmål för hållbar stadsutveckling. Frågeställningen besvarades genom att använda semistrukturerade intervjuer med fyra politiker och fyra tjänstemän från medelstora kommuner i Sverige. Resultat som framkom var att kommunerna arbetar med hållbar mobilitet i olika utsträckning utifrån olika förutsättningar och behov, men att lönsamhet och invånarnas åsikter begränsar arbetet. De slutsatser som drogs var att effektiva strategier krävs för att uppnå hållbar mobilitet vilket inkluderar ökade möjligheter för hållbart resande samt motstånd för bilanvändning. Att ha ett fungerande samarbete mellan politiker och tjänstemän samt ha en sakkunnig person på plats ansågs även vara viktiga prioriteringar och åtgärder. Eftersom att kommunerna värderar ekonomisk lönsamhet och invånarnas åsikter högre än miljön krävs dessutom prioritering på att öka nationell styrning och att regeringen måste sätta hårdare krav på kommuner. / Road traffic creates several negative consequences for the environment but also for human health. Municipalities are responsible for local infrastructure and are therefore a significant part of the work with sustainable urban development. The study examined how politicians and civil servants in Sweden's medium-sized municipalities work to make the car less attractive and to increase sustainable mobility. The study was based on Sweden's environmental goals and the strategy that includes new milestones targets for sustainable urban development. The method consisted of semi-structured interviews with four politicians and four civil servants from medium-sized municipalities in Sweden. The results showed that municipalities work with sustainable mobility to different extents based on different conditions and needs, but that profit and residents opinion limit the work. The conclusions were that effective strategies are required to achieve sustainable mobility which includes increased opportunities for sustainable travel and resistance to car use. Having a functioning collaboration between politicians and civil servants and having an expert on site were also considered important priorities and measures. Since economic profit and residents' opinion is valued higher than the environment by the municipalities, it is necessary to prioritize the implementation of national governance and that the government must set demands on municipalities.

Starke Kopplung von Molekülen mit einem räumlich begrenzten Lichtfeld führt zur Bildung neuer polaritonischer Eigenzustände des Systems, die sowohl molekulare als auch photonische Eigenschaften erhalten und somit ein großes Potenzial für Anwendungen in der Chemie und Optoelektronik besitzen. In dieser Arbeit wird die Kopplung zwischen Oberflächenplasmonen Polaritonen (SPPs), die als das räumlich begrenzte Lichtfeld agieren, und molekularen Anregungen wie Schwingungen und polaronischen Resonanzen untersucht. Das starke Kopplungsregime zwischen einer Molekülschwingung und einem SPP wird zum ersten Mal im mittleren Infrarot unter Verwendung der Carbonylschwingung von Poly(vinylmethylketon) Polymer und Silber als Ausbreitungsmedium von SPPs demonstriert. Die neu gebildeten Hybridmoden werden durch Experimente und numerische Modellierung untersucht, wobei Messungen der abgeschwächten Totalreflexion und der thermischen Emission sowie Berechnungen mittels der Transfermatrix und der linearen Dispersionstheorie verwendet werden. Ein Anticrossing in der Dispersion der Polariton-Zweige mit einer Energieaufspaltung bis zu 15 meV, was die Hauptsignatur des starken Kopplungsregimes ist, wird beobachtet. Die starke Kopplung mit Zinkgalliumoxid, einem hochdotierten Halbleiter als Alternative zu Edelmetallen, wird auch untersucht. Experimentelle und simulierte Reflektometrie-Spektren sowie Dispersionsrelationen werden diskutiert, um Rückschlüsse auf die Eigenschaften des Systems zu ziehen. Außerdem wird ein Ansatz zur Verbesserung der Leitfähigkeit organischer Halbleiterpolymere durch starke Kopplung ihrer polaronischen Zustände an SPPs vorgestellt und Leitfähigkeitsmessungen durchgeführt. Ziel ist es, die Delokalisierung der Hybridzustände auszunutzen, um die Leitfähigkeit zu verändern. Die präsentierten Ergebnisse bieten neue Einblicke in den Nutzen der Eigenschaften der Licht-Materie-Hybridisierung, um ihr volles Potenzial für verschiedene Bereiche und Anwendungen zu erforschen. / Strong coupling of molecules with a confined light field results in the formation of new polaritonic eigenstates of the system called polaritons that inherit both molecular and photonic characteristics and thus holds strong potential for applications in chemistry and optoelectronics. In this work, coupling between propagating surface plasmon polaritons (SPPs), as confined light field, and molecular excitations, such as vibrational resonances and polaronic features, is investigated. The strong coupling regime between a molecular vibration and a propagating SPP is demonstrated for the first time in the mid-infrared spectral range using the carbonyl stretch vibration of Poly(vinyl methyl ketone) polymer and silver as metallic medium for SPPs propagation. The newly formed hybrid modes are investigated through experiments and numerical modelling, employing attenuated-total-reflection and thermal emission measurements as well as transfer-matrix and linear dispersion theory calculations. An anticrossing behavior in the dispersion of the polariton branches with an energy splitting up to 15meV, which is a key signature of the strong coupling regime, is observed. Strong coupling involving zinc gallium oxide, which is a highly doped semiconductor, as an alternative to noble metals is also investigated. Experimental and simulated reflectometry spectra as well as the dispersion relations are discussed so as to draw conclusions about the properties of the system. Furthermore, an approach to enhance the conductivity of organic semiconductor polymers by strongly coupling their polaronic states to SPPs is presented and four-point probe measurements are conducted. The goal is to exploit the delocalization of the hybrid states to alter the conductivity of the organic semiconductor. The results presented in this thesis provide new insights into the profit from the properties of light-matter hybridization in order to explore its full potential for several areas and applications.

This thesis demonstrates that the composite cascode differential stage, operating in the subthreshold region, can form the basis of a high gain (113 dB) and low-power op amp (28.1 µW). The circuit can be fabricated without adding a compensation capacitance. The advantages of this architecture include high voltage gain, low bandwidth, low harmonic distortion, low quiescent current and power, and small chip area. These advantages suggest that this design might be well-suited for biomedical applications where low power, low noise bio-signal amplifiers capable of amplifying signals in the millihertz-to-kilohertz range is required.