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Dissertations / Theses on the topic 'Electrodynamics'
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1
Golz, Marcel. "Parametric quantum electrodynamics." Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/19776.
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In dieser Dissertation geht es um Schwinger-parametrische Feynmanintegrale in der Quantenelektrodynamik. Mittels einer Vielzahl von Methoden aus der Kombinatorik und Graphentheorie wird eine signifikante Vereinfachung des Integranden erreicht. Nach einer größtenteils in sich geschlossenen Einführung zu Feynmangraphen und -integralen wird die Herleitung der Schwinger-parametrischen Darstellung aus den klassischen Impulsraumintegralen ausführlich erläutert, sowohl für skalare Theorien als auch Quantenelektrodynamik. Es stellt sich heraus, dass die Ableitungen, die benötigt werden um Integrale aus der Quantenelektrodynamik in ihrer parametrischen Version zu formulieren, neue Graphpolynome enthalten, die auf Zykeln und minimalen Schnitten (engl. "bonds") basieren. Danach wird die Tensorstruktur der Quantenelektrodynamik, bestehend aus Dirac-Matrizen und ihren Spuren, durch eine diagrammatische Interpretation ihrer Kontraktion zu ganzzahligen Faktoren reduziert. Dabei werden insbesondere gefärbte Sehnendiagramme benutzt. Dies liefert einen parametrischen Integranden, der über bestimmte Teilmengen solcher Diagramme summierte Produkte von Zykel- und Bondpolynomen enthält. Weitere Untersuchungen der im Integranden auftauchenden Polynome decken Verbindungen zu Dodgson- und Spannwaldpolynomen auf. Dies wird benutzt um eine Identität zu beweisen, mit der sehr große Summen von Sehnendiagrammen in einer kurzen Form ausgedrückt werden können. Insbesondere führt dies zu Aufhebungen, die den Integranden massiv vereinfachen.This thesis is concerned with the study of Schwinger parametric Feynman integrals in quantum electrodynamics. Using a variety of tools from combinatorics and graph theory, significant simplification of the integrand is achieved. After a largely self-contained introduction to Feynman graphs and integrals, the derivation of the Schwinger parametric representation from the standard momentum space integrals is reviewed in full detail for both scalar theories and quantum electrodynamics. The derivatives needed to express Feynman integrals in quantum electrodynamics in their parametric version are found to contain new types of graph polynomials based on cycle and bond subgraphs. Then the tensor structure of quantum electrodynamics, products of Dirac matrices and their traces, is reduced to integer factors with a diagrammatic interpretation of their contraction. Specifically, chord diagrams with a particular colouring are used. This results in a parametric integrand that contains sums of products of cycle and bond polynomials over certain subsets of such chord diagrams. Further study of the polynomials occurring in the integrand reveals connections to other well-known graph polynomials, the Dodgson and spanning forest polynomials. This is used to prove an identity that expresses some of the very large sums over chord diagrams in a very concise form. In particular, this leads to cancellations that massively simplify the integrand.
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Hauck, John C. "Electrodynamics of accelerated systems /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3101024.
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Viehmann, Oliver. "Multi-qubit circuit quantum electrodynamics." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-160998.
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Kainth, Dherminder Singh. "Electrodynamics of mesoscopically structured systems." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624371.
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Ferris, Michael Raymond. "Problems in point charge electrodynamics." Thesis, Lancaster University, 2012. http://eprints.lancs.ac.uk/76343/.
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This thesis consists of two parts. In part I we consider a discrepancy in the derivation of the electromagnetic self force for a point charge. The self force is given by the Abraham-von Laue vector, which consists of the radiation reaction term proportional to the 4-acceleration, and the Schott term proportional to the 4-jerk. In the point charge framework the self force can be defined as an integral of the Lienard-Wiechert stress 3-forms over a suitably defined worldtube. In order to define such a worldtube it is necessary to identify a map which associates a unique point along the worldline of the source with every field point of the worldline. One choice of map is the Dirac time, which gives rise to a spacelike displacement vector field and a Dirac tube with spacelike caps. Another choice is the retarded time, which gives rise to a null displacement vector field and a Bhabha tube with null caps. In previous calculations which use the Dirac time the integration yields the complete self force, however in previous calculations which use the retarded time the integration produces only the radiation reaction term and the Schott term is absent. We show in this thesis that the Schott term may be obtained using a null displacement vector providing certain conditions are realized. Part II comprises an investigation into a problem in accelerator physics. In a high energy accelerator the cross-section of the beampipe is not continuous and there exist geometric discontinuities such as collimators and cavities. When a relativistic bunch of particles passes such a discontinuity the field generated by a leading charge can interact with the wall and consequently affect the motion of trailing charges. The fields acting on the trailing charges are known as (geometric) wakefields. We model a bunch of particles as a one dimensional continuum of point charges and by calculating the accumulated Lienard-Wiechert fields we address the possibility of reducing wakefields at a collimator interface by altering the path of the beam prior to collimation. This approach is facilitated by the highly relativistic regime in which lepton accelerators operate, where the Coulomb field given from the Lienard-Wiechert potential is highly collimated in the direction of motion. It will be seen that the potential reduction depends upon the ratio of the bunch length to the width of the collimator aperture as well as the relativistic factor and path of the beam. Given that the aperture of the collimator is generally on the order of millimetres we will see that for very short bunches, on the order of hundredths of a picosecond, a significant reduction is achieved.
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Habibian, Hessam. "Cavity Quantum Electrodynamics with Ultracold Atoms." Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/120180.
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Die vorliegende Arbeit befasst sich mit der Wechselwirkung ultrakalter Atome mit
der Mode eines optischen Resonators hoher Güte. Die Atome sind dabei in einem
periodischen Potenzial gefangen, dessen Periodizität nicht kommensurabel mit der
Wellenlänge des Resonators ist. Ein Laser regt die Atome an und sie streuen Photonen
in die Resonatormode, wobei die Emission inkohärent ist, falls die Laue-
Bedingung nicht erfüllt ist. Dieser Fall wird betrachtet und es werden Bedingungen
ermittelt, für welche nichtlineare optische Prozesse auftreten können. Die Eigenschaften
des Lichtes werden untersucht, wenn sich das System entweder wie ein
parametrischer Verstärker verhält oder wie eine Lichtquelle mit "Antibunching"-
Statistik. Weiterhin kann eine stationäre Verschränkung zwischen Licht und Spinwellen
der Atome erzeugt werden. Im zweiten Teil wird die Situation betrachtet,
in der die Nullpunktsbewegung der Atome für die Atom-Licht-Wechselwirkung relevant
ist. Für große Parameterbereiche zeigen numerische Berechnungen, dass die
Rückwirkung des Resonators die Formierung eines lokalen Schachbrettmusters in
der atomaren Dichteverteilung erzeugt. Die einzelnen Atomgruppe dieses Musters
stehen zueinander in fester Phasenbeziehung, was zur Erhöhung der Zahl der Resonatorphotonen
führt.In this thesis we investigate the interactions between ultracold atoms confined by a periodic potential and a mode of a high-finesse optical cavity whose wavelength is incommensurate with the potential periodicity. The atoms are driven by a probe laser and can scatter photons into the cavity field. When the von-Laue condition is not satisfied, there is no coherent emission into the cavity mode. We consider this situation and identify conditions for which different nonlinear optical processes can occur. We characterize the properties of the light when the system can either operate as a degenerate parametric amplifier or as a source of antibunched light. Moreover, we show that the stationary entanglement between the light and spinwavemodes of the array can be generated. In the second part we consider the regime in which the zero-point motions of the atoms become relevant in the dynamics of atom-photon interactions. Numerical calculations show that for large parameter regions, cavity backaction forces the atoms into clusters with a local checkerboard density distribution. The clusters are phase-locked to one another so as to maximize the number of intracavity photons.
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Liléo, Sónia. "Auroral electrodynamics of plasma boundary regions." Doctoral thesis, KTH, Rymd- och plasmafysik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10446.
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The electrodynamic coupling between the auroral ionosphere and the magnetosphere is the main subject of this thesis. Satellite measurements of electric and magnetic fields and of charged particles are used to explore three distinct plasma boundaries, magnetically linked to the nightside auroral ionosphere. These boundaries are the inner edge of the plasma sheet (PS), and the inner and the outer edges of the plasma sheet boundary layer (PSBL). Strong ionospheric electric fields with amplitudes up to 400 mV/m may be observed in the subauroral ionosphere, in the vicinity of the ionospheric projection of the PS inner edge. Intense and dynamic auroral electric fields with local magnitudes up to 150 mV/m associated with upward ion beams and field-aligned currents are observed for the events treated here, at the inner and outer boundaries of the PSBL at an altitude of about 4-5 Earth radii, well above the acceleration region. Subauroral and auroral electric fields are the two main subjects of this thesis. Subauroral ion drifts (SAID) are associated with poleward electric fields, occurring predominantly in the premidnight region during the substorm recovery phase. The recently revealed abnormal subauroral ion drifts (ASAID) are associated with equatorward electric fields, occurring during extended periods of low auroral activity. The results indicate that the generation mechanism of SAID can neither be regarded as a pure voltage generator nor a pure current generator, but having certain characteristics of both generator types. Ionospheric feedback appears to play a major role for the development and maintenance of the SAID electric fields. The formation of ASAID is proposed to result from the proximity and interaction between different plasma boundaries of the innermost magnetosphere during extended periods of low auroral activity. The auroral electric fields observed in the upward current region at the PSBL inner and outer edges are associated with upward parallel electric fields, which partially decouple the high-altitude electric fields from the ionosphere. This is in contrast to the subauroral electric fields which are coupled. Multi-point measurements provided by the Cluster mission show that the observed electric fields are highly variable in space and time, revealing various types of acceleration processes. However, they appear to be tied to the boundary where they are originally formed. A case is presented where they are associated with large electromagnetic energy fluxes directed upward away from the ionosphere. The interaction between the magnetosphere and ionosphere, being more pronounced at plasma boundary regions, is important for the understanding of the formation and regulation of the highly structured auroral electric fields observed in the upward current region.QC 20100727
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Mansuripur, Masud. "Optical angular momentum in classical electrodynamics." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/625947.
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Invoking Maxwell's classical equations in conjunction with expressions for the electromagnetic (EM) energy, momentum, force, and torque, we use a few simple examples to demonstrate the nature of the EM angular momentum. The energy and the angular momentum of an EM field will be shown to have an intimate relationship; a source radiating EM angular momentum will, of necessity, pick up an equal but opposite amount of mechanical angular momentum; and the spin and orbital angular momenta of the EM field, when absorbed by a small particle, will be seen to elicit different responses from the particle.
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Stanwix, Paul Louis. "Testing local Lorentz invariance in electrodynamics." University of Western Australia. School of Physics, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0100.
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[Truncated abstract] This thesis presents the design, construction and operation of a new rotating mod- ern Michelson-Morley test of Lorentz invariance. The experiment measures the isotropy of the speed of light by comparing the frequencies of two orthogonally ori- ented cryogenic sapphire whispering gallery mode resonators. Putative violations of Lorentz invariance will manifest as periodic variations in the difference frequency between the two resonators, related to the changing orientation of the experiment with respect to a preferred cosmological frame. Actively rotating the experiment is advantageous for three reasons. Firstly, by careful selection of the rotation frequency in the laboratory we are able to sample the isotropy of the speed of light at a rate that coincides with the optimal frequency instabilities of the oscillators (18 seconds). Secondly, the statistics of this exper- iment are improved with respect to non-rotating (stationary) experiments, which rely on the motion of the Earth to sample the isotropy of the speed of light. This results from integrating over more periods of rotation per unit of time, compared to the sidereal rotation experienced by stationary experiments. ... Many noise sources and systematic disturbances have been characterized and the operation of the experiment optimized. Two frequencies are generated at 10 GHz with 226 kHz separation, exhibiting a fractional frequency instability of less than 2x10-14 from 5 to 500 seconds. Furthermore, the work includes a detailed analysis of the experiment within the Standard Model Extension and Robertson, Mansouri and Sexl frameworks. The sensitivity of the experiment to violations of Lorentz invariance has been derived in each of these frameworks, for both short data set and the complete full year analysis. The data has been analysed using two separate data analysis techniques, which were optimised for noise present in the data. We have operated the experiment over the course of more than one year, collect- ing data more than 30 percent of the time. By analysing over 1 year of data we were able to set the first independent limits on 8 parameters in the photon sector of the Standard Model Extension as low as 10-16 for Ke- and 10-12 for Ko+ parameters, improving upon previous non-rotating experiments by up to an order of magnitude. We have also set new a new limit on the isotropy parameter PMM = 9.4(8.1)x10-11 of the Robertson, Mansouri and Sexl framework, which is a factor of 25 improvement.
10
Beere, W. H. "Electrodynamics of a charged Bose-gas." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596522.
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This thesis is a comprehensive study of the charged Bose-gas (CBG). Special attention has been paid to the role of Bose-Einstein condensation, and it's effect on the superconducting properties of the system. The main motivation for this work has been the relevance of the CBG as a model for the high temperature superconductors, within the context of the bipolaron theory[1], the experimental and theoretical evidence for which is discussed in the introductory chapters. By using standard many body theory relevant properties of the CBG have been derived. Much attention has been placed on how to deal with the condensate in an interacting system. The Bogoliubov-de Gennes (BdG) equations are formulated for the Charged Bose Gas (CBG), and their extension to the Ginzburg-Landau-Abrikosov-Gor'kov (GLAG) type theory is discussed. The temperature dependence of the condensate density for the Coulomb Bose-gas (CBG) was studied using the Bogoliubov approximation. This enabled the calculation of the London penetration depth as a function of temperature. Other thermodynamic variables, such as the free energy and specific heat, were also calculated. The nature of the Bose-Einstein condensation of the CBG in a magnetic field was investigated for ultra-low temperatures and ultra-high magnetic fields. The temperature dependence of the upper critical field was found to have positive curvature, one of the remarkable features of the high temperature superconductors. The difference between the resistive transition and the peak in the specific heat is also discussed.
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Kannan, Bharath. "Waveguide quantum electrodynamics with superconducting qubits." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120400.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 85-87).
Experiments in quantum optics have long been implemented with atoms in 3D free space or with atoms interacting with cavities. Over the past decade, the field of microwave quantum optics using superconducting circuits has gained a tremendous amount of attention. In particular, the confinement of photonic modes to 1D enables a new parameter regime of strong interactions between qubits and open waveguides. In these setups, known as waveguide quantum electrodynamics (WQED), superconducting qubits interact with a continuum of propagating photonic modes. In this thesis, we will explore the physics of WQED devices that consist of multiple qubits and their potential application to quantum information and simulation.
by Bharath Kannan.
S.M.
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Broun, David McBride. "The microwave electrodynamics of unconventional superconductors." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621767.
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Kohler, Shane Jerome. "Non-linear effects in quantum electrodynamics." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5279.
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Diniz, Igor. "Quantum electrodynamics in superconducting artificial atoms." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENY048/document.
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This thesis focuses on two problems in circuit quantum electrodynamics. We first investigate theoretically the coupling of a resonator to a continuous distribution of inhomogeneously broadened emitters. Studying this formalism is strongly motivated by recent proposals to use collections of emitters as quantum memories for individual excitations. Such systems benefit from the collective enhancement of the interaction strength, while keeping the relaxation properties of a single emitter. We discuss the influence of the emitters inhomogeneous broadening on the existence and on the coherence properties of the polaritonic peaks. We find that their coherence depends crucially on the shape of the distribution and not only on its width. Taking into account the inhomogeneous broadening allows to simulate with a great accuracy a number of pioneer experimental results on a ensemble of NV centers. The modeling is shown to be a powerful tool to obtain the properties of the spin ensembles coupled to a resonator. We also suggest an original Josephson qubit readout method based on a dc-SQUID with high loop inductance. This system supports a diamond-shape artificial atom where we define logical and ancilla qubits coupled through a cross-Kerr like term. Depending on the logical qubit state, the ancilla is resonantly or dispersively coupled to the resonator, leading to a large contrast in the transmitted microwave signal amplitude. Simulations show that this original method can be faster and have higher fidelity than methods currently used in circuit QEDCette thèse porte sur deux problèmes théoriques d'électrodynamique quantique en circuits supraconducteurs. Nous avons d'abord étudié les conditions d'obtention du couplage fort entre un résonateur et une distribution continue d'émetteurs élargie de façon inhomogène. Le développement de ce formalisme est fortement motivé par les récentes propositions d'utiliser des ensembles de degrés de liberté microscopiques pour réaliser des mémoires quantiques. En effet, ces systèmes bénéficient du couplage collectif au résonateur, tout en conservant les propriétés de relaxation d'un seul émetteur. Nous discutons l'influence de l'élargissement inhomogène sur l'existence et les propriétés de cohérence des pics polaritoniques obtenus dans le régime de couplage fort. Nous constatons que leur cohérence dépend de façon critique de la forme de la distribution et pas uniquement de sa largeur. En tenant compte de l'élargissement inhomogène, nous avons pu simuler avec une grande précision de nombreux résultats expérimentaux pionniers sur un ensemble de centres NV. La modélisation s'est révélée un outil puissant pour obtenir les propriétés des ensembles de spins couplés à un résonateur. Nous proposons également une méthode originale de mesure de l'état de qubits Josephson fondée sur un SQUID DC avec une inductance de boucle élevée. Ce système est décrit par un atome artificiel avec des niveaux d'énergie en forme de diamant où nous définissons les qubits logique et ancilla couplés entre eux par un terme Kerr croisé. En fonction de l'état du qubit logique, l'ancilla est couplée de manière résonante ou dispersive au résonateur, ce qui provoque un contraste important dans l'amplitude du signal micro-onde transmis par le résonateur. Les simulations montrent que cette méthode originale peut être plus rapide et peut aussi avoir une plus grande fidélité que les méthodes actuellement utilisées dans la communauté des circuits supraconducteurs
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Грицунов, А. В., И. Н. Бондаренко, А. Б. Галат, О. В. Глухов, and А. Г. Пащенко. "On the quantum electrodynamics of nanosystems." Thesis, Kharkiv, bookfabrik, 2019. http://openarchive.nure.ua/handle/document/10408.
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Problems of quantum dynamics of nanoobjects essential for development of new nanoelectronic systems are discussed. According to the theory of natural oscillatory systems (NOSs), “interaction” between the objects is interpreted as a quantum-dynamic phenomenon meaning a stable trend arising from the quantum chaos. As an opposite, “interchange” is denominated as the permanent stochastic exchange with action quanta between different NOSs in 4D spacetime, being the physical base of the quantum chaos. The Tetrode-Wheeler-Feynman’s concept of “direct interparticle action” is reconciled with both the quantum radiation-absorption and the Coulomb interaction. A conservation law for the action is supposed as a necessary condition for the momentum-energy conservation. The “classic” conservation law for the momentum-energy is considered as derivative, being valid for the momentum as well as some physical value that is an integral over 3D space from a linear combination of stress-energy tensor principal diagonal terms. Such redefinition enables the unconditional quantization of the energy unlike “orthodox” quantum theory.
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Liléo, Sónia. "Auroral electrodynamics of plasma boundary regions /." Stockholm : Skolan för elektro- och systemteknik, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10446.
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Dordevic, Sasa V. "Electrodynamics of strongly correlated electron systems /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3044790.
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Jeantet, Adrien. "Cavity quantum electrodynamics with carbon nanotubes." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC010/document.
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Les nanotubes de carbone sont largement étudiés pour leurs propriétés mécaniques et électroniques étonnantes. Optiquement, ils sont d'excellents candidats pour les sources à un seul photon à la demande car ils peuvent être excités électriquement et ils peuvent émettre une lumière dégroupée à température ambiante dans les bandes de télécommunications. Cependant, leur efficacité d'émission est faible, les origines de l'émission restent peu claires et la forme spectrale de leur photoluminescence est compliquée.Dans ce travail, nous construisons une configuration originale combinant un microscope confocal et une micro-cavité à base de fibres optiques qui est à la fois spatialement et spectralement réglable. Avec ce dispositif, nous avons observé l'apparition des effets de l'électrodynamique quantique en cavité en analysant l'évolution du couplage dipôle-cavité en fonction du volume de la cavité. Nous avons obtenu une forte accélération du taux d'émission spontanée, grâce à des facteurs Purcell supérieurs à 100. L'efficacité effective associée de la source atteint jusqu'à 50%, conduisant à une luminosité jusqu'à 10%, tout en conservant d'excellentes caractéristiques de dégroupement.Nous observons l'effet du couplage de la cavité en fonction du désaccord de la cavité et développons un modèle pour tenir compte des émetteurs soumis au couplage exciton-phonon en présence d'une cavité. Nous montrons que notre source de photons uniques est accordable sur une gamme de fréquences plus de cent fois supérieure à la largeur spectrale de la cavité, ouvrant ainsi la voie à un multiplexage étendu.Un renforcement supplémentaire du couplage peut ouvrir la voie à la très riche physique des polaritons de cavité unidimensionnels. Inversement, les polaritons de cavité pourraient être un outil pour mieux comprendre la diffusion et les propriétés de localisation des excitons dans les nanotubes de carbone. Enfin, la configuration initiale ici est extrêmement polyvalente et pourrait être utilisée pour coupler d'autres types d'émetteurs, comme les nano-diamants ou les moléculesCarbon nanotubes are extensively investigated for their amazing mechanical and electronic properties. Optically, they are excellent candidates for on-demand single-photon sources because they can be electrically excited and they can emit anti-bunched light at room temperature in the telecoms bands. However, their emission efficiency is low, its origins remain unclear and the spectral shape of their photoluminescence is complicated. In this work, we build an original setup combining a confocal microscope and a fiber based micro-cavity which is both spatially and spectrally tunable. With this device, we observed the rise of cavity quantum electrodynamics effects by analyzing the evolution of the dipole-cavity coupling as a function of the cavity volume. We obtained a strong acceleration of the spontaneous emission rate, due to Purcell factors above 100. The associated effective efficiency of the source reaches up to 50%, leading to a brightness of up to 10%, while keeping excellent anti-bunching features. We observe the effect of the cavity coupling as a function of the cavity detuning, and develop a model to account for emitters undergoing exciton-phonon coupling in the presence of a cavity. We show that our single-photon source is tunable on a range of frequencies more than a hundred times higher than the cavity spectral width, opening the way to extensive multiplexing. Further strengthening of the coupling may open the way to the very rich physics of one-dimensional cavity polaritons. And conversely, cavity polaritons could be a tool to understand better the diffusion, and localization properties of excitons in carbon nanotubes. Finally, the original setup build here is extremely versatile and could be used to coupled other types of emitters, such as nano-diamonds or molecules
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Petry, Robert George. "Atomic field electrodynamics and classical radiation reaction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0008/MQ34986.pdf.
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Baxter, Colin. "Gauge transformations in non-relativistic quantum electrodynamics." Thesis, University of Essex, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292876.
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Pieterse, Cornelius Louwrens. "Mathematical and numerical analysis of electrospraying electrodynamics." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95529.
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Thesis (MEng) -- Stellenbosch University, 2014ENGLISH ABSTRACT: The electrodynamics of arbitrary, point-to-plane electrospraying geometries, were investigated in this research both analytically and numerically. Electrospraying is the process during which particles of sizes in the nanometre range are simultaneously generated and charged by means of an applied electrostatic field. A high electrostatic potential is applied to a conductive capillary needle, which overcomes the force exerted by the liquid surface tension. One of the primary limitations of this process are corona discharges. The effect of corona discharges have not been studied quantitatively, even though it is frequently reported in the electrospraying literature. The main objective of this research was to understand the corona discharge thresholds associated with electrospraying. Previously, only one theoretical, and two empirical investigations studied this phenomenon, over a time period of approximately forty years. It was clear that by better understanding these thresholds, electrospraying could be applied much more effectively. A corona discharge threshold model is proposed, using either a numerical or analytical model for the calculation of polarization fields. When compared with the experimental results of other researchers, both these two models have average relative percentage errors of approximately 15%. These are the first models proposed in the literature for the calculation of electrospraying corona thresholds. A new method to determine surface tension using electrospraying is described theoretically. In addition to this method, the calculation of corona discharge thresholds have various applications. For example, the dynamics of electrostatic ion thrusters are much better described, powder production by means of electrospraying can be optimised, and pattern generation using pulsed electrospraying cone-jets can be optimised as well.
AFRIKAANSE OPSOMMING: Die elektrodinamika van arbitrêre, punt-tot-vlak elektrosproei geometrieë was beide analities en numeries ondersoek in hierdie tesis. Dit is die proses waartydens nanodeeltjies gelyktydig gegenereer en elektrostaties gelaai word. Deur 'n hoë elektriese potensiaal aan te lê tot 'n geleidende kapillêr, is dit moontlik om die krag van die oppervlakte spanning te oorkom. Een van die primêre beperkings van elektrosproei is corona ontladings. Die effek van corona ontladings was nog nie kwantitatief bestudeer nie, selfs al word dit dikwels rapporteer in die elektrosproei literatuur. Die primêre doel van hierdie navorsing was om die corona ontlading drempels te verstaan wat geassosieer word met elektrosproei. In die verlede was daar nog net een teoretiese, en twee empiriese ondersoeke gewees wat hierdie verskynsel bestuur het, oor 'n tydperk van ongeveer veertig jaar. Dit was duidelik dat deur 'n beter begrip te hê van hierdie elektrosproei drempels, kan hierdie proses baie meer doeltreffend toegepas word. In hierdie tesis word 'n corona ontlading drempel model voorgestel, wat gebruik maak van 'n analitiese of numeriese model om die polarisasie velde te bereken. Wanneer vergelyk met die resultate van ander navorsers, het beide die modelle 'n gemiddelde relatiewe persentasie fout van ongeveer 15%. Hierdie is die eerste modelle wat voorgestel word vir die berekening van corona ontlading drempels. Deur gebruik te maak van elektrosproei, word 'n nuwe metode ook voorgestel om die oppervlakte spanning te bereken. In byvoeging tot hierdie, het die berekening van corona ontlading drempels vele ander toepassings. As 'n voorbeeld, die dinamika van elektrostatiese ioon stuwers word beter beskryf, en poeier produksie deur middel van elektrosproei kan optimeer word.
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Lepert, Guillaume. "Integrated optics for coupled-cavity quantum electrodynamics." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/11175.
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This thesis reports on the development of an array of plane-concave Fabry-Perot microcavities containing atoms (or other quantum emitters), interconnected by UV-written waveguides on a silica-on-silicon chip. The microcavities are formed by a mirror coated on the end facet of the chip and an array of spherical micromirrors etched on silicon. This is to our knowledge the first attempt at implementing the emerging coupled-cavities QED paradigm. The device we propose possesses a degree of control, flexibility and tuning unmatched in other suggested implementations: The atoms can be manipulated inside the cavity by auxiliary lasers and the cavity-cavity coupling rate as well as the atom-cavity coupling can be tuned. It is highly scalable. Calculation of the complete (classical) optical spectrum of the device is presented. The quantum dynamics that may eventually be observed has also been studied. Waveguide chips containing couplers and phase shifter have been fabricated. We have successfully demonstrated the operation of the elementary sub-systems: the strong optical coupling between a microcavity and a waveguide resonator, and the tunable strong coupling between two evanescently coupled waveguide resonators. No experiments with atoms or other quantum emitters were attempted, because the waveguide propagation loss is so large that no quantum physics can be observed. There is hope that this can be overcome in the future by using other waveguide technologies.
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Frenzel, Alex J. "Terahertz Electrodynamics of Dirac Fermions in Graphene." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17467397.
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Charge carriers in graphene mimic two-dimensional massless Dirac fermions with linear energy dispersion, resulting in unique optical and electronic properties. They exhibit high mobility and strong interaction with electromagnetic radiation over a broad frequency range. Interband transitions in graphene give rise to pronounced optical absorption in the mid-infrared to visible spectral range, where the optical conductivity is close to a universal value $\sigma_0 = \pi e^2/2h$. Free-carrier intraband transitions, on the other hand, cause low-frequency absorption, which varies significantly with charge density and results in strong light extinction at high carrier density. These properties together suggest a rich variety of possible optoelectronic applications for graphene.
In this thesis, we investigate the optoelectronic properties of graphene by measuring transient photoconductivity with optical pump-terahertz probe spectroscopy. We demonstrate that graphene exhibits semiconducting positive photoconductivity near zero carrier density, which crosses over to metallic negative photoconductivity at high carrier density. These observations are accounted for by the interplay between photoinduced changes of both the Drude weight and carrier scattering rate. Our findings provide a complete picture to explain the opposite photoconductivity behavior reported in (undoped) graphene grown epitaxially and (doped) graphene grown by chemical vapor deposition. Our measurements also reveal the non-monotonic temperature dependence of the Drude weight in graphene, a unique property of two-dimensional massless Dirac fermions.Physics
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Walker, Philip. "Radiation and reaction in scalar quantum electrodynamics." Thesis, University of York, 2010. http://etheses.whiterose.ac.uk/996/.
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This thesis is a report of work which develops the study of electromagnetic radiation by accelerating charges in the scalar quantum electrodynamic theory. We investigate aspects of this theory in flat spacetime, and in a class of conformally flat and curved spacetimes. In particular, we show that in flat spacetime, the quantum-theoretic prediction for the emission of energy by the particle, in the limit h-bar tends to 0 and to order e^2 in the coupling constant, may be shown to match the classical calculation. We also calculate the order h-bar correction to this quantity for two specific classes of problem. In the class of conformally flat and curved spacetimes, we compare the change in position due to the radiation reaction with the classical result, and we also consider some of the one-loop corrections to the theory. We show that as h-bar tends to 0, the conformally flat result and the classical result match, but that in that limit the general spacetime results differ.
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Barlow, Thomas Michael. "Cavity quantum electrodynamics of fibre-cavity networks." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/12646/.
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Quantum mechanics, despite its abstract and unintuitive nature, is increasingly used in real-life applications. This thesis explores the current status of cavity quantum electrodynamics and its role in applications of quantum optics to quantum technologies. Various approaches to the treatment of optical cavities are discussed, with particular focus on a treatment in terms of cavities as linear optical devices, with a nonlinearity introduced by an atom, molecule, quantum dot etc in the cavity. Open quantum systems such as optical cavities coupled to a free external radiation field can be described by a quantum master equation. This thesis develops a description of such a system in which the Hamiltonian describes the coherent evolution of light inside the cavity, and the damping term describes the leaking of light out of the cavity mirrors. The goal of this approach is to describe couple networks of optical cavities in which information is transferred across the network coherently.
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Raji, Rufai Odutayo. "Nonlinear low frequency wave phenomena in space plasmas." Thesis, University of the Western Cape, 2013. http://hdl.handle.net/11394/4036.
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Philosophiae Doctor - PhDIn this thesis, using multispecies fluid plasma models, nonlinear electrostatic solitary wave fluctuations will be investigated in magnetized plasmas. The different models used for the investigation will be guided by the satellite observations in different regions of the Earth magnetosphere. These investigations will enable us to attempt theoretical explanations for the nonlinear potential structures observed in the satellite data. Multispecies plasma consisting of cool and hot electrons with Maxwellian distributions and fluid ions will be considered to study low frequency solitons. The ions will be considered as magnetized. The study will be extended to include magnetized oxygen ions. The model will be modified for regions of the magnetosphere consisting of two ions having Maxwellian distributions and magnetized electrons. The nonthermal distributions of energetic hot electrons and the Maxwellian distributions of cool electrons with magnetized cold ions fluid will also be considered. For all the models, the effect of ion and electron densities, temperatures, magnetic field strength and propagation angle will be studied during the investigation of soliton structures. In all the above mentioned studies, arbitrary amplitude theory is carried out by the Sagdeev pseudo-potential method. Further investigations on the charateristics and existence domains of the solitons is found both analytically and numerically, using satellite data where applicable
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Carlson, Andrew F. "Optimal orbit maneuvers with electrodynamic tethers." Thesis, Monterey, Calif. : Naval Postgraduate School, 2006. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Sep%5FCarlson.pdf.
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Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, June 2006.Thesis Advisor(s): Ross, I. Michael ; Danielson, Don A. "June 2006." Description based on title screen as viewed on November 7, 2007. Includes bibliographical references (p. 65-67). Also available in print.
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Wild, James. "Electrodynamics of the auroral ionosphere during magnetospheric substorms." Thesis, University of Leicester, 2000. http://hdl.handle.net/2381/30641.
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One of the principal consequences of magnetic reconnection at the dayside magentopause is the transfer of solar wind energy in the Earth's magnetotail. The expansion phase of a magnetospheric substorm corresponds to the sudden release of this energy and is characterised in the ionosphere by the sudden brightening and poleward expansion of the auroral oval near midnight and the intensification of the ionospheric currents flowing in the auroral zone. Observations of various high-latitude ionospheric phenomena associated with magnetospheric substorm are presented. In particular, use is made of the Co-operative UK Twin Located Auroral Sounding System (CUTLASS), a high frequency bistatic coherent-scatter radar with sites in Finland and Iceland. Azimuthally Propagating Vortical Currents (APVCs) are the ionospheric flow signatures of upward directed field-aligned currents in the nightside ionosphere. Two case studies of APVCs are presented and their structure examined in detail. In addition, the results of a statistical study of APVC occurrence encompassing over 1000 hours of high-time resolution data are discussed with particular focus on the relationship of APVCs to magnetospheric substorm phase. Omega bands are a distinct class of auroral form that have previously been observed in the morning sector during the recovery phase of magnetospheric substorms. High-time resolution measurements of the ionospheric flow within a series of omega bands from the CUTLASS Finland radar are presented. Complementary observations from the Scandinavian Twin Auroral Radar Experiment (STARE) and ground magnetometers of the IMAGE array are employed in order to characterise the electric and magnetic field structure of omega bands. Revised descriptions of omega band structure and formation mechanism are proposed. Finally, multi-instrument observations of the evolution of a high-latitude polar auroral arc during the recovery phase of an isolated substorm are presented and its relation to upstream interplanetary magnetic field conditions discussed.
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Ho, Andy C. T. "Imaginary charge quantum electrodynamics : a running coupling analysis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0005/NQ34551.pdf.
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Nadeau, Raymond. "Two-loop effective potential of supersymmetric quantum electrodynamics." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75872.
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The formalism of effective potential method is first studied for usual field theory and extended to supersymmetric field theory. The specific case of supersymmetric quantum electrodynamics is then introduced. The superfields are shifted as required by Weinberg's method for the evaluation of effective potentials and superpropagators are derived with the method developed by Helayel-Neto for cases where supersymmetry is explicitly broken. Then, the one and two loop corrections to the effective potential may be calculated. These corrections are seen to be complex everywhere but at the minimum of the potential. Tile theory is then renormalized in a modified minimal substraction scheme and a finite expression is finally obtained for the effective potential. Thereon, the renormalized coupling constant and the $ beta$-function are calculated.
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Braverman, Boris. "Cavity quantum electrodynamics with ensembles of ytterbium-171." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120364.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 313-328).
In this thesis, I present the realization of a system applying the tools of cavity quantum electrodynamics to an atomic optical lattice clock. We design and implement a unique experimental cavity structure, with a small radius of curvature mirror on one side and a large mirror on the other side. With this structure, we are able to probe ytterbium-171 atoms in both the weak and strong coupling regimes of cavity quantum electrodynamics. This asymmetric micromirror structure simultaneously offers strong light-atom coupling, mechanical robustness, and excellent access to a large cavity volume. We develop a simple but accurate model for strong light-atom interactions in our system, which allows us to predict the performance of both cavity-assisted quantum non demolition measurements of the atomic state, and the back-action of the probing light onto the atomic state. We find theoretically, and confirm experimentally, that probing the atom-cavity system with two frequencies at the vacuum Rabi peaks of a system with strong collective light-atom coupling generates the largest possible entanglement between the probing light and the atomic state. With this scheme, we demonstrate atomic number measurements within a factor of 2 of the quantum Fisher information limit. By using the quantum back-action of the probing light on the atomic ensemble, we perform squeezing by cavity feedback. We produce states with -11±1 dB of variance squeezing and 14±1 dB of anti squeezing. Using theoretical simulations, we show that states with near-unitary squeezing offer significant advantages for improving atomic clocks compared to previous work. The ability to load large atomic ensembles in the strong coupling regime in our system offers several routes to the generation of highly entangled non-Gaussian quantum states. Such states can be produced by heralded measurements, or by global atom-atom interactions based on unitary spin squeezing. Altogether, we realize a system of unprecedented versatility and great potential for performing a large variety of hybrid atomic clock and cavity QED experiments.
by Boris Braverman.
Ph. D.
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Golyk, Vladyslav Alexander. "Non-equilibrium fluctuation induced-phenomena in quantum electrodynamics." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91076.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2014.138
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 120-129).
We study fluctuation-induced phenomena in systems out of thermal equilibrium, resulting from the stochastic nature of quantum and thermal fluctuations of electromagnetic currents and waves. Specifically, we study radiative heat transfer and Casimir forces by applying the scattering formalism that expresses results solely in terms of the classical scattering matrices of the objects. For example, we obtain exact formulas for the heat radiation emitted by long cylindrical objects, as well as for Casimir forces that arise between them. We apply our results to explore the dependence of these phenomena on size and material properties of cylinders. While the scattering formalism is very general and technically can be employed for arbitrary shapes, in practice it is very time-consuming to apply it to the most experimentally-relevant and complex case of objects at close proximity. We examine easier ways to compute the heat transfer in such case. In particular, we develop a small distance expansion for the heat transfer between gently curved objects, in terms of the ratio of distance to radius of curvature. This expansion allows us to rigorously justify the widely used approach of "proximity transfer approximation", and to quantify corrections to it in the limit of small separation. Moreover, we study the role of surface roughness, and show that it may change the distance dependence of the heat transfer as well as Casimir forces between curved objects at proximity. Finally, as an alternative approach we construct general Green-Kubo relations that connect radiative heat transfer, non-equilibrium Casimir forces and vacuum friction between arbitrary objects to fluctuations in equilibrium which may be easier to consider from the perspective of experiment and simulations.
by Vladyslav Alexander Golyk.
Ph. D.
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Dakers, Paul A. "Superlattice electrodynamics as a source of Terahertz radiation." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/10228.
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Charge-carriers propagating in superlattices exhibit the related phenomena known as negative differential conductivity and Bloch oscillation. This behaviour may be utilised for the generation of tunable electromagnetic radiation. In this work, the dependence of the drift velocity and displacement of charge-carriers on external, applied electric fields is investigated. The theory is extended to incorporate a different miniband structure, with the aim of modelling a superlattice made from graphene. I predict that, for a chosen set of electric field parameters, a semiconductor superlattice will emit radiation in the terahertz range. I create an original mathematical framework within which to calculate the charge-carrier behaviour in a triangular miniband structure, while incorporating an arbitrary variable to account for the effects of corrugation or disorder, and predict the appearance of conductivity multistability. This may be of interest to further work done on the use of graphene for superlattice device construction.
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Holland, Eric T. "Cavity State Reservoir Engineering in Circuit Quantum Electrodynamics." Thesis, Yale University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10012490.
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Engineered quantum systems are poised to revolutionize information science in the near future. A persistent challenge in applied quantum technology is creating controllable, quantum interactions while preventing information loss to the environment, decoherence. In this thesis, we realize mesoscopic superconducting circuits whose macroscopic collective degrees of freedom, such as voltages and currents, behave quantum mechanically. We couple these mesoscopic devices to microwave cavities forming a cavity quantum electrodynamics (QED) architecture comprised entirely of circuit elements. This application of cavity QED is dubbed Circuit QED and is an interdisciplinary field seated at the intersection of electrical engineering, superconductivity, quantum optics, and quantum information science. Two popular methods for taming active quantum systems in the presence of decoherence are discrete feedback conditioned on an ancillary system or quantum reservoir engineering. Quantum reservoir engineering maintains a desired subset of a Hilbert space through a combination of drives and designed entropy evacuation. Circuit QED provides a favorable platform for investigating quantum reservoir engineering proposals. A major advancement of this thesis is the development of a quantum reservoir engineering protocol which maintains the quantum state of a microwave cavity in the presence of decoherence. This thesis synthesizes strongly coupled, coherent devices whose solutions to its driven, dissipative Hamiltonian are predicted a priori. This work lays the foundation for future advancements in cavity centered quantum reservoir engineering protocols realizing hardware efficient circuit QED designs.
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Zhang, Ou. "Effective field theories for quantum chromo- and electrodynamics." Thesis, The University of Arizona, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10247445.
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Effective field theories (EFTs) provide frameworks to systematically improve perturbation expansions in quantum field theory. This improvement is essential in quantum chromodynamics (QCD) predictions, both at low energy in the description of low momentum hadron-hadron scattering and at high energy in the description of electron-positron, proton-proton, proton-electron collisions. It is also important in quantum electrodynamics (QED), when electrons interact with a high-intensity, long-wavelength classical field. I introduce the principles and methods of effective field theory and describe my work in three EFTs: First, in the perturbative QCD region, I use soft collinear effective theory (SCET) to prove that strong interaction soft radiation is universal and to increase the QCD accuracy to next-to-next-to-next-to leading logarithm order for new particle searches in hadron colliders. I also compute a new class of non-perturbative, large logarithmic enhancement arising near the elastic limits of deep inelastic scattering and Drell-Yan processes. Second, in the QCD confinement region, I use heavy hadron chiral perturbation theory to study near-threshold enhancements in the scattering of D and π mesons near the threshold for the excited D-meson state, D*, as well as in the scattering of D and D* mesons near the threshold for the exotic hadron X(3872). This work provides a clear picture of the hadronic molecule X(3872) and more profound understanding of the nuclear force between hadrons. Finally, inspired by SCET, I construct a new electron-laser effective field theory to describe highly-relativistic electrons traveling in strong laser fields, extract the universal distribution of electrons in strong electromagnetic backgrounds and its evolution in energy from the separated momentum scales of emitted photons and classical radiation, and predict the rate of wide angle photon emission. I conclude with limitations of EFT methods and some perspectives on what new work may be achieved with these EFTs.
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Zhang, Ou, and Ou Zhang. "Effective Field Theories for Quantum Chromo- and Electrodynamics." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621825.
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Effective field theories (EFTs) provide frameworks to systematically improve perturbation expansions in quantum field theory. This improvement is essential in quantum chromodynamics (QCD) predictions, both at low energy in the description of low momentum hadron-hadron scattering and at high energy in the description of electron-positron, proton-proton, proton-electron collisions. It is also important in quantum electrodynamics (QED), when electrons interact with a high-intensity, long-wavelength classical field. I introduce the principles and methods of effective field theory and describe my work in three EFTs: First, in the perturbative QCD region, I use soft collinear effective theory (SCET) to prove that strong interaction soft radiation is universal and to increase the QCD accuracy to next-to-next-to-next-to leading logarithm order for new particle searches in hadron colliders. I also compute a new class of non-perturbative, large logarithmic enhancement arising near the elastic limits of deep inelastic scattering and Drell-Yan processes. Second, in the QCD confinement region, I use heavy hadron chiral perturbation theory to study near-threshold enhancements in the scattering of 𝐷 and 𝜋 mesons near the threshold for the excited 𝐷-meson state, 𝐷*, as well as in the scattering of 𝐷 and 𝐷* mesons near the threshold for the exotic hadron X(3872). This work provides a clear picture of the hadronic molecule X(3872) and more profound understanding of the nuclear force between hadrons. Finally, inspired by SCET, I construct a new electron-laser effective field theory to describe highly-relativistic electrons traveling in strong laser fields, extract the universal distribution of electrons in strong electromagnetic backgrounds and its evolution in energy from the separated momentum scales of emitted photons and classical radiation, and predict the rate of wide angle photon emission. I conclude with limitations of EFT methods and some perspectives on what new work may be achieved with these EFTs.
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Cardoso, Lucas Tavares. "Towards renormalizability of string-localized massive quantum electrodynamics." Universidade Federal de Juiz de Fora (UFJF), 2017. https://repositorio.ufjf.br/jspui/handle/ufjf/5621.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
A construção de campos com localização em cordas foi realizada rigorosamente há pouco mais de uma década. Nesta abordagem, os campos são operadores em algum espaço de Hilbert, e portanto não há graus de liberdade não-físicos tais como "ghosts". Além de permitir a construção de campos carregados inteiramente num espaço espaço de Hilbert, os campos com localização em cordas exibem um bom comportamento no regime ultravioleta e, entre outras características, são possíveis candidatos para descreverem consistentemente a matéria escura. No intuito de obter uma prova da renormalizabilidade em modelos perturbativos no esquema de Epstein-Glaser com campos quânticos localizados em cordas, é necessário evidenciar a liberdade que se tem ao definir produtos temporalmente ordenados do Lagrangeano de interação. Este trabalho proporciona um primeiro passo significativo nesta direção. O problema básico é a presença de um conjunto aberto de n-uplas de cordas que não podem ser cronologicamente ordenadas. Nós resolvemos este problema ao mostrar que quase todas (i.e. exceto num subconjunto de medida nula) tais configurações de cordas podem ser dissecadas num número finito de pedaços, os quais por sua vez podem ser cronologicamente ordenados. Com isso, tem-se que o produto temporalmente ordenado de fatores lineares de campos está fixo fora de um conjunto de medida nula de configurações de cordas. A construção do ordenamento temporal geométrico de cordas é feita de modo a servir para o estudo da renormalizabilidade de quaisquer teorias quânticas de campos com localização em cordas.
The construction of string-localized fields was rigorously accomplished a little over a decade ago. In this approach, the fields are operators in some Hilbert space, and therefore there are no unphysical degrees of freedom such as ghosts. In addition to allowing the construction of charged fields entirely in a Hilbert space, the string-localized fields exhibit, in general, a good behavior in the ultraviolet regime and, among other features, the class (representation) of string-localized fields with m = 0 and s = oo are possible candidates to consistently describe dark matter. In order to obtain a proof of renormalizability of perturbative models in the Epstein—Glaser scheme with string-localized quantum fields, one needs to know what freedom one has to define time-ordered products of the interaction Lagrangian. This work provides a first significant step in that direction. The basic issue is the presence of an open set of n-tuples of strings which cannot be chronologically ordered. We resolve it by showing that almost all (i.e. outside a null set) such string configurations can be dissected into finitely many pieces which can indeed be chronologically ordered. This fixes the time-ordered products of linear field factors outside a nullset of string configurations. The construction of the geometric time ordering of strings is realized in such a way that it will serve to study the renormalizability of any quantum field theories with string-localized fields
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Asker, Andreas. "Axion Electrodynamics and Measurable Effects in Topological Insulators." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-67519.
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Topological insulators are materials with their electronic band structure in bulk resembling that of an ordinary insulator, but the surface states are metallic. These surface states are topologically protected, meaning that they are robust against impurities. The topological phenomena of three dimensional topological insulators can be expressed within topological field theories, predicting axion electrodynamics and the topological magnetoelectric effect. An experiment have been suggested to measure the topological phenomena. In this thesis, the underlying theory and details around the experiment are explained and more detailed derivations and expressions are provided.
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Stokes, Adam. "On gauge freedom and subsystems in quantum electrodynamics." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/6833/.
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I analyse different decompositions of composite light-matter systems into constituent subsystems. I show that given a single description of a composite atomfield system, many different decompositions into “atom” and “field” subsystems can be made. I show that these decompositions are generally physically inequivalent, and that they can be understood as corresponding to different choices of gauge. I discuss some of the implications this has for the ontology of QED, and find experimental signatures that could be used to distinguish between different theoretical subsystem decompositions.
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Flatten, Lucas Christoph. "Quantum electrodynamics of semiconducting nanomaterials in optical microcavities." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:a5f4797f-ea23-49e4-bd1e-2483154508d6.
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Semiconducting nanocrystals in open-access microcavities are promising systems in which enhanced light-matter interactions lead to quantum effects such as the modulation of the spontaneous emission process and exciton-polariton formation. In this thesis I present improvements of the open cavity platform which serves to confine the electromagnetic field with mode volumes down to the λ3 regime and demonstrate results in both the weak and strong coupling regimes of cavity quantum electrodynamics with a range of different low-dimensional materials. I report cavity fabrication details allowing a peak finesse of 5 × 104 and advanced photonic structures such as coupled cavities in the open cavity geometry. By incorporating two-dimensional materials and nanoplatelets in the cavity I demonstrate the strong coupling regime of light-matter interaction with the formation of exciton-polaritons, quasi-particles composed of both photon and exciton, at room temperature. In the perturbative weak coupling regime I show pronounced modulation of the single-photon emission from CdSe/ZnS quantum dots and the two-dimensional material WSe2 and demonstrate Purcell enhancement of the spontaneous emission rate by factors of 2 at room temperature and 8 at low temperature. The findings presented in this thesis pave the way to establish open microcavities as a platform for a wide range of applications in nanophotonics and quantum information technologies.
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Wohlwend, Christian Stephen. "Modeling the Electrodynamics of the Low-Latitude Ionosphere." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/11.
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The electrodynamics of the Earth's low-latitude ionosphere is dependent on the ionospheric conductivity and the thermospheric neutral density, temperature, and winds present. This two-part study focused on the gravity wave seeding mechanism of equatorial plasma depletions in the ionosphere and the associated equatorial spread F, as well as the differences between a two-dimensional flux tube integrated electrodynamics model and a three-dimensional model for the same time period. The gravity wave seeding study was based on a parameterization of a gravity wave perturbation using a background empirical thermosphere and a physics-based ionosphere for the case of 12 UT on 26 September 2002. The electrodynamics study utilized a two-dimensional flux tube integrated model in center dipole coordinates, which is derived in this work. This case study examined the relative influence of the zonal wind, meridional wind, vertical wind, temperature, and density perturbations of the gravity wave. It further looked at the angle of the wave front to the field line flux tube, the most influential height of the perturbation, and the difference between planar and thunderstorm source gravity waves with cylindrical symmetry. The results indicate that, of the five perturbation components studied, the zonal wind is the most important mechanism to seed the Rayleigh-Taylor instability needed to develop plasma plumes. It also shows that the bottomside of the F-region is the most important region to perturb, but a substantial E-region influence is also seen. Furthermore, a wave front with a small angle from the field line is necessary, but the shape of the wave front is not critical in the gravity wave is well developed before nightfall. Preliminary results from the three-dimensional model indicate that the equipotential field line assumption of the two-dimensional model is not valid below 100 km and possibly higher. Future work with this model should attempt to examine more of the differences with the two-dimensional model in the electric fields and currents produced as well as with the plasma drifts that lead to plume development.
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Watts, Frank. "The effect of electrical potential on drop formation : a basis for an automated interfacial tensionmeter." Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/10122.
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Wood, Jeffrey C. "An analysis of mixed finite element methods for Maxwell's equations on non-uniform meshes." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282161.
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Brown, Solly. "The photon model of the quantum electromagnetic field /." [St. Lucia, Qld.], 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16777.pdf.
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Marghitu, Octav. "Auroral arc electrodynamics with FAST satellite and optical data." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=967869188.
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López, Bara Fernando Ignacio. "Electrodynamics and phase transitions in materials with magnetic monopoles." Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/665231.
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El trabajo está dirigido a analizar dos aspectos que están intrínsecamente relacionados. El primero se refiere al estudio de los estados globales y característicos de las estructuras magnéticas de los compuestos denominados “spin-ices” y el segundo se analizan los comportamientos bajo interacción electromagnética en medios infinitos y en sistemas confinados.
La principal novedad de estos compuestos es la existencia de estados excitados globales a bajas temperaturas en los cuales surgen entidades estructurales que mimetizan el comportamiento de monopolos magnéticos. En la primera parte del trabajo, los estados excitados de baja temperatura son estudiados en compuestos del tipo (ETR)₂Ti₂ O₇, dónde ETR se refiere a uno de los diversos lantánidos, principalmente Dy₂Ti₂O₇ y Ho₂Ti₂O₇ . A temperaturas comprendidas entre 0.05K a 0.17K, hay una transición de fase con características similares a un condensado Bose-Einstein cuyos componentes individuales están constituidos por dipolos magnéticos (dos monopolos, una carga magnética positiva y la otra negativa conectados por la interacción Coulombiana y separados por una distancia equivalente a la altura de cada tetraedro de la estructura cristalina la cual es descrita en el texto). Al incrementar la temperatura, dichos dipolos se rompen formando un plasma magnético de cargas positivas y negativas libres o cuasi libres cuya estadística es del tipo Fermi-Dirac. Los procesos de transición termodinámica son descritos por modelos analíticos para estados excitados de baja energía y la descripción de las sucesivas transiciones de fase. Se han determinado los potenciales termodinámicos, calor específico y entropía con los cuales se pueden mostrar las posibles transiciones de fase que ocurren en estos compuestos.
En la segunda parte, se realiza un análisis de las ecuaciones de Maxwell modificadas, así como de la fuerza de Lorentz generalizada ante la presencia de estas cargas magnéticas. La solución de estas ecuaciones nos permite obtener resultados que podrían tener interés empírico con tal de detectar monopolos magnéticos en otros compuestos naturales. Se ha estudiado la propagación transversal electromagnética en estos materiales al añadir un intenso campo eléctrico externo que permite deducir la densidad de monopolos por unidad de volumen y la masa efectiva de los mismos.
Hemos deducido las soluciones de las ecuaciones duales de Maxwell en medios confinados con simetrías rectangular y cilíndrica. En dichos medios en fase de plasma magnético, se ha obtenido la ecuación no lineal del parámetro de orden del sistema. Las características y propiedades de las soluciones de las ecuaciones de Maxwell modificas han sido determinados en los modos TM, obteniendo la conductividad magnética como una función dependiente de la frecuencia (llamada Magnetricidad); susceptibilidad magnética, tanto como picos de absorción electromagnética, y otras variables como la frecuencia de precesión y la frecuencia característica del plasma o frecuencia del plasmón. El poder obtener dichas frecuencias no ha permitido determinar la masa específica de estas cuasi partículas, siendo básica esta magnitud física para determinar y justificar las propiedades de conducción.
El objetivo fundamental de esta parte ha sido poder realizar un análisis sistemático para detectar en otros materiales la presencia de posibles cargas magnéticas efectivas que pudieran aparecer en otros compuestos artificiales a temperatura ambiente, con el interés práctico que esta novedad podría implicar. Por tanto, la finalidad de la segunda parte de la tesis es encaminar un futuro estudio de posibles nuevos materiales que permitiesen construir dispositivos “magnetrónicos” que posibilitaran la transmisión de energía e información.The work is addressed to analyze two parts that are intimately related. The first one refers to studying the global states and characteristics of their magnetic structures of the compounds called spin-ices and in the second part the behaviors under the electromagnetic interaction in infinite media and in confined systems are analyzed. The main novelty in these compounds is the existence of excited global states at low-temperatures in which structural entities that mimic the behavior of magnetic monopoles arise. In the first part, the low temperature excited states or quasiparticles are studied in compounds of the type (REE)₂Ti₂ O₇, where REE refers to one of the 15 lanthanides, fundamentally Dy₂Ti₂O₇ andHo₂Ti₂O₇. At these temperatures (between 0.05 K and 0.17 K) there is a phase transition with characteristics similar to a Bose Einstein condensate whose individual components are in the form of magnetic dipoles (two monopoles, one with positive magnetic charge and the other negative connected by the "Coulomb interaction" and separated by a distance equivalent to the high of each tetrahedron of the crystalline structure which we described in the text). By increasing the temperature, said dipoles are broken forming a magnetic plasma of free and quasi-free positive and negative magnetic charges whose statistic is of the Fermi-Dirac type. The thermodynamic transition processes are described by analytical models for low energy excitation states and we describe the successive phase transitions. We determine the thermodynamic potentials, specific heat and entropy in which we can show the two possible phase transitions that occur in these compounds. In the second part, we make an analysis of the modified Maxwell equations as well as the generalized Lorentz force in the presence of these magnetic charges. The solution of these equations allows us to obtain data that may have empirical interest in order to detect magnetic monopoles in other natural compounds. We study the transverse electromagnetic propagation in these materials by adding a strong external electric field with which we deduce the density of monopoles per unit volume and the effective mass of the same. We deduce the solutions of these dual Maxwell equations in confined media with rectangular and circular symmetries. In these media in the magnetic plasma phase we obtain the non-linear equation of the system order parameter. The characteristics and properties of the solutions of the modified Maxwell equations are determined in the form of TM modes, obtaining magnetic conductivity as a function of frequency (called magnetricity), magnetic susceptibility, as well as peaks in electromagnetic absorption and other data such as the frequencies of precession and the characteristic frequency of plasma or frequency of plasmon. The achieving of these two frequencies allows us to determine the specific mass assigned to these quasiparticles, being physical magnitude is basic for determining and justifying the conduction properties. The fundamental objective of this part is to perform a systematic analysis to detect in other materials the presence of these possible effective magnetic charges that may appear and have appeared in other artificial compounds even at room temperature, with the practical interest that this novelty may have. The last objective of this second part of the thesis is to make a prospective to study the possibilities of new materials with which to build "magnetronic" devices that allow to transmit energy and information.
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Helmer, Ferdinand. "Quantum information processing and measurement in circuit quantum electrodynamics." Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-102919.
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Tignone, Edoardo. "Cavity quantum electrodynamics : from photonic crystals to Rydberg atoms." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAF008/document.
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Dans le premier chapitre de la thèse, nous étudions la possibilité d’améliorer le couplage opto- mechanique photon-phonon entre le mode de résonance d’une cavité Fabry-Pérot de haute finesse et les vibrations mécaniques des éléments diélectriques (membranes) à l’intérieur de la cavité. En introduisant un défaut quadratique dans la disposition des membranes, nous montrons que le deux couplages (linéaire et quadratique) augmentent. Enfin, nous proposons un modèle très simple avec lequel on cherche à simuler un cristal photonique quasipériodique. Dans le deuxième chapitre de cette thèse, nous présentons nos résultats de recherche sur le transport d’excitons à travers une cavité visant à augmenter l’efficacité du transport. Le modèle que l’on étudie est une chaîne unidimensionnelle d’atomes froids comprenant chacun deux niveaux énergétiques. Grâce au couplage entre exciton et photon, ces deux quanta s’hybrident et forment deux branches de polariton à l’intérieur de la cavité. Nous avons observé qu’à résonance avec un des deux modes de polariton, on peut transmettre l’exciton via le mode polaritonique dans un temps très court. En outre, le désordre n’affecte la propagation excitonique que de façon algébrique. Dans le troisième chapitre de cette thèse, nous présentons nos résultats de recherche sur la réalisa- tion d’interactions entre photons grâce à la médiation d’atomes ultrafroids piégés dans un réseaux optique unidimensionnelle et placés à l’intérieur d’une fibre à cristaux photoniques. Nous avons détecté un régime dans lequel on peut réaliser le “bunching” photon-photon.Dans le quatrième et dernière chapitre de cette thèse, nous étendons les résultats du chapitre précédent aux atomes de RydbergIn the first chapter of this thesis, we study a quasiperiodic array of dielectric membranes inside a high-finesse Fabry-Pérot cavity. We work within the framework of the transfer matrix formal- ism. We show that, in a transmissive regime, the introduction of a quadratic spatial defect in the membrane positions enhances both the linear and quadratic optomechanical couplings between optical and mechanical degrees of freedom. Finally, we propose a theoretical model to simulate a one-dimensional quasiperiodic photonic crystal. In the second chapter of this thesis, we consider the problem of the transport of an exciton through a one-dimensional chain of two-level systems. We embed the chain of emitters in a transverse optical cavity and we show that, in the strong coupling regime, a ultrafast ballistic transport of the exciton is possible via the polaritonic modes rather than ordinary hopping. Due to the hybrid nature of polaritons, the transport efficiency is particularly robust against disorder and imperfections in the system. In the third chapter of this thesis, we consider an ordered array of cold atoms trapped in an optical lattice inside a hollow-core photonic crystal fiber. We study photon-photon interactions mediated by hard-core repulsion between excitons. We show that, in spite of underlying repulsive interac- tion, photons in the scattering states demonstrate bunching, which can be controlled by tuning the interatomic separation. We interpret this bunching as the result of scattering due to the mismatch of the quantization volumes for excitons and photons, and discuss the dependence of the effect on experimentally relevant parameters. In the fourth chapter of the thesis, we extend the results of the previous chapter to Rydberg atoms
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Striet, Jelper. "Alice electrodynamics on the gauging of charge conjugation symmetry /." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2003. http://dare.uva.nl/document/67123.
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Dutra, Sergio Mendes. "Generation and detection of fields in cavity quantum electrodynamics." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307569.
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