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Dissertations / Theses on the topic 'QED'
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1
De, Souza Stephen William. "Lattice QED." Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/14759.
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We consider the question of the existence of an interacting continuum limit of Quantum Electrodynamics (QED). After a mention of why this limit may not exist and a discussion of how to formulate QED on a spacetime lattice we review the recent analytic and numerical work on the strong-coupling phase of QED. We take the view that there definitely exists a strong-coupling fixed point in the space of bare parameters but that the behaviour of renormalised quantities in its neighbourhood is not yet understood. For non-compact lattice QED with staggered fermions we develop an expansion in the inverse bare fermion mass that we use to calculate charge and fermion mass renormalisation. We evalute the vacuum polarisation to sixth order and present Feynman rules that allow its evaluation to higher orders. We also calculate the mass of the lowest lying pseudoscalar bound state and the chiral condensate. These physical quantities enable us to construct renormalisation group flow for all values of the bare charge. The expansion is checked against lattice perturbation theory and leads to a systematically improvable bound on the renormalised charge at the new fixed point. We also discuss compact QED coupled to scalars and find a chiral symmetry breaking transition at a non-zero value of the scalar coupling by using mean field theory. After establishing that this transition has Landau exponents we attempt to develop corrections to mean field theory by introducing fluctuations. The conclusion discusses the future of the large-mass expansion and lists some unresolved issues in lattice QED.
2
Gray, Norman. "Dimensionally regulated on-shell renormalisation in QCD and QED." Thesis, n.p, 1991. http://oro.open.ac.uk/19423/.
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Zemp, Peter. "Pionic hydrogen in QCD + QED : decay width at NNLO /." Bern : [s.n.], 2004. http://www.zb.unibe.ch/download/eldiss/04zemp_p.pdf.
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MANTOVANI, LUCA. "Applications of Light-Front Quantization in QED and QCD." Doctoral thesis, Università degli studi di Pavia, 2018. http://hdl.handle.net/11571/1214851.
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The goal of this thesis is to present some novel applications of the light-front quantization formalism to the fields of Quantum Electrodynamics (QED) and Quantum Chromodynamics (QCD). Light-Front quantization proves to be an elegant language for the description of a composite particle in terms of its elementary constituents; as such, it has recently become a very effective language for
Quantum Field Theories and, in particular, for Hadronic Physics. we first provide an intriduction to the light-front formalism and study the gauge-field propagator in light-cone gauge. We then introduce the partonic distribution functions on the light cone and calculate the Transverse-Momentum Dependent (TMDs) and the
Generalized TMDs (GTMDs) in the context of QED, thus obtaining a multi-dimensional picture of the electron cloud. We finally address the problem of properly defining angular-momentum densities inside the nucleon.
5
Gorbahn, Martin. "QCD and QED anomalous dimension matrix for weak decays at NNLO." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=970226101.
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Phipps, Martin. "Applications of perturbative QCD and QED using fully relativistic wave functions." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56669.
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In this thesis, a method for calculating the decay rates and branching ratios using perturbative QCD and QED is proposed. Among the assumptions used are that heavy mesons are non-relativistic quark/anti-quark bound states and that light mesons can be treated as quarks in a bag. The method will be applied to the $ eta sb{c} to phi phi$ decay and to 1-loop contributions to the leptonic widths of mesons.
7
Montero, J. C. [UNESP]. "Quebra dinamica da simetria quiral em teorias vetoriais: QED e QCD." Universidade Estadual Paulista (UNESP), 1987. http://hdl.handle.net/11449/132820.
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Montero, J. C. (Juan Carlos). "Quebra dinamica da simetria quiral em teorias vetoriais : QED e QCD /." São Paulo, 1987. http://hdl.handle.net/11449/132820.
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Bashir, Adnan. "Constructing vertices in QED." Thesis, Durham University, 1995. http://etheses.dur.ac.uk/5124/.
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We study the Dyson Schwinger Equation for the fermion propagator in the quenched approximation. We construct a non-preservative fermion-boson vertex that ensures the fermion propagator satisfies the Ward-Takahashi identity, is multiplicatively renormalizable, agrees with the lowest order perturbation theory for weak couplings and has a critical coupling for dynamical mass generation that is strictly gauge independent. This is in marked contrast to the rainbow approximation in which the critical coupling changes by 50% just between the Landau and Feynman gauges. We also show how to construct a vertex which not only has the aforementioned properties but also agrees with the results obtained from the CJT effective potential for the critical exponent of the mass function. These vertices are expressed in terms of two functions which satisfy an integral and a derivative condition. By considering the perturbative expansion for the transverse vertex, we have performed numerical evaluation of the first of these functions which will hopefully guide their non-perturbative structure. The use of vertices satisfying these properties should lead to a more believable study of mass generation.
10
Ahlig, Steven. "Analytical properties of the quark propagator QED 3, QCD and Kaon photoproduction /." [S.l. : s.n.], 2001. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB9403127.
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Martini, Ullrich. "Cavity QED with many atoms." Diss., [S.l.] : [s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=963141449.
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Boozer, Allen David Kimble H. Jeff. "Raman transitions in cavity QED /." Diss., Pasadena, Calif. : California Institute of Technology, 2005. http://resolver.caltech.edu/CaltechETD:etd-05272005-160246.
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Birnbaum, Kevin Michael Kimble H. Jeff. "Cavity QED with multilevel atoms /." Diss., Pasadena, Calif. : California Institute of Technology, 2005. http://resolver.caltech.edu/CaltechETD:etd-05272005-103306.
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Northup, Tracy Eleanor Kimble H. Jeff Kimble H. Jeff. "Coherent control in cavity QED /." Diss., Pasadena, Calif. : California Institute of Technology, 2008. http://resolver.caltech.edu/CaltechETD:etd-05242008-114227.
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Takahashi, Kazuyoshi. "D-brane physics from QED." 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/144172.
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Kyoto University (京都大学)0048
新制・課程博士
博士(理学)
甲第12089号
理博第2983号
新制||理||1445(附属図書館)
23925
UT51-2006-J84
京都大学大学院理学研究科物理学・宇宙物理学専攻
(主査)助教授 國友 浩, 教授 畑 浩之, 助教授 笹倉 直樹
学位規則第4条第1項該当
16
Williams, Richard. "Schwinger-Dyson equations in QED and QCD : the calculation of fermion-antifermion condensates." Thesis, Durham University, 2007. http://etheses.dur.ac.uk/2558/.
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We present non-perturbative solutions for the fermion and boson propagators of QED in both three- and four-dimensions, and QCD. In doing so, we solve the coupled system of Schwinger-Dyson equations numerically in Euclidean space, investigating criticality, gauge dependence and phenomenology of the solutions. We do so by exploiting a new and novel three-point ansatz, the Kizilersü-Pennington vertex, designed to satisfy multiplicative renormalisability in unquenched QED. The efficacy of this is demonstrated numerically for QED(_4), where we find a marked improvement in the gauge-invarance of the photon wave-function. The critical coupling associated with dynamical mass generation is investigated for a variety of gauges; remarkably a lessening of this dependence is seen, despite the ansatz’s origins from a massless theory, which is improved further by constructing a hybrid system. As with many studies in the past, we apply this ansatz to the three-dimensional non-compact formulation of QED, checking gauge covariance of the propagators through a momentum-space formulation of the Landau-Khalatnikov-Pradkin transformations. The critical dependence on the number of active fermions was investigated, with the gauge dependence of the condensate unresolved. As an aside, we found numerically that LKF transforming the propagators gave rise to a constant condensate; a fact supported analytically through an explicit proof. We turn our attention towards QCD, where we explore a variety of phenomeno-logical models, including the full ghost-gluon system, in which we make comparisons between traditional vertices and the new KP-Vertex. These models are used in a determination of the physical quark condensate for massive quarks, through the exploitation of a class of non-positive definite solutions accessible for small quark masses. Finally, we examine Generalised Ward-Takahashi identities, which hold promise to further constrain the tranvserse part of the vertex. The identity is shown to hold true at one-loop through an explicit calculation, and a constraint on one of the basis coefficients is given as an example of its use.
17
Kurcz, Andreas. "Qed in periodischen und absorbierenden Medien." Master's thesis, Universität Potsdam, 2005. http://opus.kobv.de/ubp/volltexte/2009/3528/.
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Das Strahlungsfeld in einem absorbierenden, periodischen Dielektrikum ist kanonisch quantisiert worden. Dabei wurde ein eindimensionales Modell mit punktförmigen Streuern betrachtet, deren Polarisierbarkeit den Kramers-Kronig Relationen gehorcht. Es wurde ein Quantisierungsverfahren nach Knöll, Scheel und
Welsch [1] verwendet, das als eine Ergänzung zum mikroskopischen Huttner-Barnett Schema [2] aufgefaßt werden kann und in dem auf der Basis der phänomenologischen Maxwell Gleichungen eine bosonische Rauschpolarisation als die Quelle des Feldes auftritt. Das Problem reduziert sich dabei auf die Bestimmung der klassischenGreens Funktion.
Die Kramers-Kronig Relationen der komplexen Polarisierbarkeit der Punktstreuer sichert die korrekte Verknüpfung zwischen Dispersion und Absorption. Der Punktstreuer ist dabei ein idealisiertes Modell, um periodische Hintergrundmedien, denen das Strahlungsfeld ausgesetzt ist, zu beschreiben. Er bedarf jedoch eines Kompromisses, um die entsprechenden Rauschquellen zu konstruieren. Es konnte gezeigt werden, daß der Punktstreuer dasselbe Streuverhalten wie eine dünne Potentialschwelle besitzt und damit die technischen Schwierigkeiten für den Fall eines absorptiven Punktstreuers überwunden werden können. An Hand dieses Beispiels konnte das Quantisierungsschema nach Knöll, Scheel und Welsch auf periodische und absorbierende Strukturen angewendet werden.
Es ist bekannt, daß die Bestimmung der Modenstruktur für den Fall der Modenzerlegung des Strahlungsfeldes ein rein klassisches Problem darstellt. Mit Ausnahme des Vakuums ist eine zweckmäßige Modenzerlegung nur dann durchführbar, wenn mit einer reellen Polarisierbarkeit die Absorption vernachlässigt werden kann. Aus den Kramers-Kronig Relationen wird klar, daß solch eine Annahme nur in bestimmten Intervallen des Frequenzspektrums gerechtfertigt werden kann. Es wurde gezeigt, daß auch das quantisierte Strahlungsfeld in Anwesenheit der Punktstreuer in eben solchen Intervallen in Quasimoden entwickelt werden kann, wenn man neue Quasioperatoren als Erzeuger und Vernichter einführt. Die bosonischen Vertauschungsrelationen dieser Operatoren konnten bestätigt werden. Die allgemeine Vertauschungsrelation kanonisch konjugierter Variablen im Sinne der kanonischen Quantisierung kann für das elektrische Feld und das Vektorpotential beibehalten werden.
In der Greens Funktion sind sämtliche Informationen über die dispersiven und absorptiven Eigenschaften des Dielektrikums sowie über die räumliche Struktur enthalten. Die wesentlichen Merkmale werden dabei durch den Reflexionskoeffizienten nach Boedecker und Henkel [3] bestimmt, der das Reflexionsverhalten an einem unendlich ausgedehnten Halbraum aus periodisch angeordneten Punktstreuern beschreibt. Mit Hilfe des Transfermatrixformalismus war es möglich einen allgemeinen Zugang zum Reflexionsverhalten zunächst endlicher Strukturen zu erhalten. Die Ausdehnung auf den Halbraum mit Hilfe der Klassifizierung in Untergruppen der Transfermatrizen nach ermöglichte es, den Reflexionskoeffizienten nach Boedecker und Henkel [3] auch geometrisch plausibel zu machen.
Ein wesentlicher Aspekt von periodischen Systemen ist die Translationssymmetrie, die im Fall unendlich ausgedehnter, verlustfreier Systeme auf eine ideale Bandstruktur führt. Mit Hilfe der Untergruppenklassifizierung kann im verlustfreien Fall die Geometrie der Anordnung indirekt mit der Bandstruktur verknüpft werden. Es konnte nachgewiesen werden, daß auch der einzelne Punktstreuer immer in einer dieser Untergruppen zu finden ist. Dabei besitzt die Bandstruktur der unendlich periodischen Anordnung dieser Streuer immer eine von der Polarisierbarkeit abhängige Bandkante und eine von der Polarisierbarkeit unabhängige Bandkante. Die Bandstruktur, die mit den verlustbehafteten Feldern einhergeht, ist eine doppelt komplexe. Alternativ zu dieser nur schwer zu
interpretierenden Bandstruktur wurden die Feldfluktuationen selektiv nach reellen Frequenzen und Wellenzahlen sondiert. Es zeigt sich, daß Absorption besonders in der Nähe der Bandkanten die Bänder verbreitert. Die Ergebnisse, die mit Hilfe der lokalen Zustandsdichtefunktion gewonnen wurden, konnten dabei
bestätigt werden.
[1] S. Scheel, L. Knöll and D. G. Welsch, Phys.Rev. A 58, 700 (1998).
[2] B. Huttner and S. M. Barnett, Phys. Rev. A 46, 4306 (1992).
[3] G. Boedecker and C. Henkel, OPTICS EXPRESS 11, 1590 (2003).A canonical scheme based on the phenomenological Maxwell equations in the presence of dielectric matter is used to quantize the electromagnetic field in a periodic and lossy linear dielectric. We focus on a one-dimensional model of point scatterers with given frequency-dependent complex permittivity, and construct an expansion of the field operators that is based on the Green function and preserves the canonical equal-time commutation relations. Translation symmetry is secured by working with an infinite lattice. The impact of absorption is examined using the local density of states and the decay rate of a phase-coherent dipole chain located inside the structure. Incidentally the model is used to bring about a geometrical interpretation of the reflection from multilayers
18
Alqahtani, Moteb M. "Multi-photon processes in cavity QED." Thesis, University of Sussex, 2014. http://sro.sussex.ac.uk/id/eprint/49632/.
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Based on a multi-mode multi-level Jaynes-Cummings model and multi-photon resonance theory, a set of universal two-qubit and three-qubit gates has been realized where dual-rail qubits are encoded in cavities. In this way, the information has been stored in cavities and the off-resonant levels have been eliminated by the theory of an effective two-level Hamiltonian. A further model, namely the spin-J model, has been introduced so that a complete population inversion for levels of interest has been achieved and periodic multilevel multi-photon models have been performed. The combination of the two models has been employed to address two-level, three-level, four-level, and even five-level configurations. Considering the present cavity-QED experiments, several numerical simulations have been designed in order to check the robustness of the logic gates to variations in experimentally important parameters including the coupling constants and the detunings. Finally, based on Liouville's equation, and the wave-function treatments, the impact of decoherence processes on the fidelity of the qubit states in the iSWAP and the Fredkin gates has been studied. This thesis may have applications to quantum information processing, involving logic with simple quantum bits, with the possible application to the building of a quantum computer.
19
Boldo, Jose Luis [UNESP]. "Dinâmica assintótica na 'QED IND.3'." Universidade Estadual Paulista (UNESP), 1996. http://hdl.handle.net/11449/132542.
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Boldo, Jose Luis. "Dinâmica assintótica na 'QED IND.3' /." São Paulo : [s.n.], 1996. http://hdl.handle.net/11449/132542.
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Blackburn, Thomas George. "QED effects in laser-plasma interactions." Thesis, University of Oxford, 2015. http://ora.ox.ac.uk/objects/uuid:d026b091-f278-4fbe-b27e-bd6af4a91b7a.
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It is possible to reach the radiation-reaction–dominated regime in today’s high-intensity laser facilities, using the collision of a wakefield-accelerated GeV electron beam with a 30 fs laser pulse of intensity 1022 Wcm-2. This would demonstrate that the yield of high energy gamma rays is increased by the stochastic nature of photon emission: a beam of 109 electrons will emit 6300 photons with energy > 700 MeV, 60 times the number predicted classically. Detecting those photons, or a prominent low energy peak in the electron beam's post-collision energy spectrum, will provide strong evidence of quantum radiation reaction; we place constraints on the accuracy of timing necessary to achieve this. This experiment would provide benchmarking for the simulations that will be used to study the plasmas produced in the next generation of laser facilities. With focused intensities > 1023 Wcm-2, these will be powerful enough to generate high fluxes of gamma rays and electron-positron pairs from laser–laser and laser–solid interactions. It will become possible to test the physics of exotic astrophysical phenomena, such as pair cascades in pulsar magnetospheres, and explore fundamental aspects of quantum electrodynamics (QED). To that end we will discuss: classical theories of radiation reaction; QED processes in intense fields; and a Monte Carlo algorithm by which the latter may be included in particle-in-cell codes. The feedback between QED processes and classical plasma dynamics characterises a new regime we call QED-plasma physics.
22
Armen, Michael A. Mabuchi Hideo Mabuchi Hideo. "Bifurcations in single atom cavity QED /." Diss., Pasadena, Calif. : California Institute of Technology, 2009. http://resolver.caltech.edu/CaltechETD:etd-05262009-100436.
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Carrazza, S. "PARTON DISTRIBUTION FUNCTIONS WITH QED CORRECTIONS." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/284820.
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We present the first unbiased determination of parton distribution functions (PDFs) with electroweak corrections. The aim of this thesis is to provide an exhaustive description of the theoretical framework and the technical implementation which leads to the determination of a set of PDFs which includes the photon PDF and quantum electrodynamics (QED) contributions to parton evolution. First, we introduce and motivate the need of including electroweak corrections to PDFs, providing phenomenological examples and presenting an overview of the current state of the art in PDF fits. The theoretical implications of such corrections are then described through the implementation of the combined QCDxQED evolution in APFEL, a public code for the solution of the PDF evolution developed particularly for this thesis. We proceed by presenting the new structure of the Neural-Network PDF (NNPDF) methodology used for the extraction of this set of PDFs with QED corrections. We then provide a first determination of the full set of PDFs based on deep-inelastic scattering data and LHC data for W and Z/γ* Drell-Yan production, using leading-order QED and NLO or NNLO QCD: the so-called NNPDF2.3QED set of PDFs. We perform a preliminary investigation of the phenomenological implications of NNPDF2.3QED set, in particular, focusing on the photon-induced corrections to direct photon production at HERA, high-mass dilepton and W pair production at the LHC and finally, providing a first determination of lepton PDFs through the APFEL evolution. We conclude with a summary of the technological upgrades required for the improvement of future PDF determinations with electroweak corrections.
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Lange, Birgit. "Resonator-QED-Experimente mit einzelnen 40Ca+-Ionen." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-67486.
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Zebarjad, Seyyed Mohammad. "Positronium hyperfine splitting corrections using nonrelativistic QED." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ44643.pdf.
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Terraciano, Matthew Louis. "Cross-correlations and entanglement in cavity QED." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3767.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Larson, Jonas. "Extended Jaynes-Cummings Models In Cavity Qed." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-404.
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Baldwin, Charles H. "Cavity QED with Center of Mass Tunneling." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1312237577.
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Kim, Soo Y. "Cold single atoms for cavity QED experiments." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26581.
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Thesis (Ph.D)--Physics, Georgia Institute of Technology, 2009.Committee Chair: Chapman, Michael; Committee Member: Citrin, David; Committee Member: Kennedy, T. A. Brian; Committee Member: Kuzmich, Alexander; Committee Member: Raman, Chandra. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Connolly, Elizabeth Wilcut Kimble H. Jeff Kimble H. Jeff. "Experiments with toroidal microresonators in cavity QED /." Diss., Pasadena, Calif. : California Institute of Technology, 2009. http://resolver.caltech.edu/CaltechETD:etd-05282009-101209.
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Labun, Lance. "Structure and Decay in the QED Vacuum." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/203491.
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This thesis is a guide to a selection of the author's published work that connect and contribute to understanding the vacuum of quantum electrodynamics in strong, prescribed electromagnetic fields. This theme is elaborated over the course of two chapters: The first chapter sets the context, defining the relevant objects and conditions of the study and reviewing established knowledge upon which this study builds. The second chapter organizes and explains important results appearing in the published work. The papers 1. (Labun and Rafelski, 2009) "Vacuum Decay Time in Strong External Fields" 2. (Labun and Rafelski, 2010a) "Dark Energy Simulacrum in Nonlinear Electrodynamics" 3. (Labun and Rafelski, 2010b) "QED Energy-Momentum Trace as a Force in Astrophysics" 4. (Labun and Rafelski, 2010c) "Strong Field Physics: Probing Critical Acceleration and Inertia with Laser Pulses and Quark-Gluon Plasma" 5. (Labun and Rafelski, 2010d) "Vacuum Structure and Dark Energy" 6. (Labun and Rafelski, 2011) "Spectra of Particles from Laser-Induced Vacuum Decay" are presented in their published format as appendices. Related literature is cited throughout the body where it directly supports the content of this overview; more extensive references are found within the attached papers. This study begins with the first non-perturbative result in quantum electrodynamics, a result obtained by Heisenberg and Euler (1936) for the energy of a zero-particle state in a prescribed, long-wavelength electromagnetic field. The resulting Euler-Heisenberg effective potential generates a nonlinear theory of electromagnetism and exhibits the ability of the electrical fields to decay into electronpositron pairs. Context for phenomena arising from the Euler-Heisenberg effective potential is established by considering the energy-momentum tensor of a general nonlinear electromagnetic theory. The mass of a field configuration is defined, and I discuss two of its consequences pertinent to efforts to observe vacuum decay. I develop a method for non-perturbative evaluation of a trace component of the energymomentum tensor and discuss its significance and consequences. I study the effect of the energy-momentum trace as part of a Euler-Heisenberg-generated modification to the Lorentz force. Modifications of the energy-momentum tensor from the Maxwell theory are evaluated numerically and compared to those arising from Born-Infeld electromagnetism and the Euler-Heisenberg effective potential for a scalar electron. Finally, I explore how this study guides investigation into how vacuum structure can generate the cosmological dark energy.
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Dotsenko, Igor. "Single atoms on demand for cavity QED experiments." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=984484124.
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Zschocke, Sven. "Die Zwei-Photonen-Selbstenergie und andere QED-Strahlungskorrekturen." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-29621.
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Die genaue Messung der Lamb-Verschiebung stark gebundener Elektronen in Zusammenhang mit Tests der Quantenelektrodynamik (QED) in starken Feldern in hochgeladenen Ionen ist eines der Hauptthemen der heutigen Atomphysik. Die gegenwärtig durchgeführten Hochpräzisionsmessungen erfordern eine hohe Genauigkeit in den theoretischen Berechnungen der Lamb-Verschiebung. Diese Genauigkeit impliziert eine Berücksichtigung aller QED-Korrekturen der Ordnung α und α2, aber exakt in allen Ordnungen in Z&α. In den zurückliegenden Jahren sind die meisten dieser QED-Korrekturen sowohl in 1. Ordnung als auch in 2. Ordnung Störungstheorie berechnet worden. Der Beitrag der Zwei-Photonen-Selbstenergie konnte jedoch bisher nicht ausgewertet werden und stellte somit die größte Ungenauigkeit in der Vorhersage der Lamb-Verschiebung für wasserstoffartige Systeme dar. In dieser Arbeit wird der Beitrag dieser Prozesse zur Lamb-Verschiebung untersucht. Darüber hinaus werden erstmals renormierte Ausdrücke der Zwei-Photonen-Vakuumpolarisation und der Selbstenergie-Vakuumpolarisation hergeleitet. Bisher konnten diese Beträge nur in Uehling-Näherung ausgewertet werden.
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Lundin, Joakim. "QED and collective effects in vacuum and plasmas." Doctoral thesis, Umeå universitet, Institutionen för fysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-35615.
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The theory of quantum electrodynamics (QED) was born out of an attempt to merge Einsteins theory of special relativity and quantum mechanics. Einsteins energy/mass equivalence together with Heisenberg's uncertainty principle allows for particle pairs to be spontaneously created and annihilated in vacuum. These spontaneous fluctuations gives the quantum vacuum properties analogous to that of a nonlinear medium. Although these fluctuations in general does not give note of themselves, effects due to their presence can be stimulated or enhanced through external means, such as boundary conditions or electromagnetic fields. Whereas QED has been very well tested in the high-energy, low-intensity regime using particle accelerators, the opposite regime where the photon energy is low but instead the intensity is high is still to a large degree not investigated. This is expected to change with the rapid progress of modern high-power laser-systems. In this thesis we begin by studying the QED effect of photon-photon scattering. This process has so far not been successfully verified experimentally, but we show that this may change already with present day laser powers. We also study QED effects due to strong magnetic fields. In particular, we obtain an analytical description for vacuum birefringence valid at arbitrary field strengths. Astrophysics already offer environments where QED processes may be influential, e.g. in neutron star and magnetar environments. For astrophysical purposes we investigate how effects of QED can be implemented in plasma models. In particular, we study QED dispersive effects due to weak rapidly oscillating fields, nonlinear effects due to slowly varying strong fields, as well as QED effects in strongly magnetized plasmas. Effects of quantum dispersion and the electron spin has also been included in an extended plasma description, of particular interest for dense and/or strongly magnetized systems.
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Zebarjad, Seyyed Mohammad. "Positronium hyperfine splitting corrections using non-relativistic QED." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35425.
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We use Nonrelativistic Quantum Electrodynamics (NRQED) as an effective field theory to calculate the single photon annihilation contribution to the positronium hyperfine splitting (HFS) in its ground state at order Oa6 . Our analytical result completes the hyperfine splitting calculation to order mea6 . Using NRQED, we derive the Lamb shift of a scalar-scalar bound state and Oa5 hyperfine splitting of positronium for a general excited state. Using the same technique, we also rederive the Lamb shift of Hydrogen atom and Oa5 HFS of positronium in its ground state.
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Seipt, Daniel. "Strong-Field QED Processes in Short Laser Pulses." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-103705.
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The purpose of this thesis is to advance the understanding of strong-field QED processes in short laser pulses. The processes of non-linear one-photon and two-photon Compton scattering are studied, that is the scattering of photons in the interaction of relativistic electrons with ultra-short high-intensity laser pulses. These investigations are done in view of the present and next generation of ultra-high intensity optical lasers which are supposed to achieve unprecedented intensities of the order of 10^24 W/cm^2 and beyond, with pulse lengths in the order of some femtoseconds.
The ultra-high laser intensity requires a non-perturbative description of the interaction of charged particles with the laser field to allow for multi-photon interactions, which is beyond the usual perturbative expansion of QED organized in powers of the fine structure constant. This is achieved in strong-field QED by employing the Furry picture and non-perturbative solutions of the Dirac equation in the presence of a background laser field as initial and final state wave functions, as well as the laser dressed Dirac-Volkov propagator.
The primary objective is a realistic description of scattering processes with regard to the finite laser pulse duration beyond the common approximation of infinite plane waves, which is made necessary by the ultra-short pulse length of modern high-intensity lasers. Non-linear finite size effects are identified, which are a result of the interplay between the ultra-high intensity and the ultra-short pulse length. In particular, the frequency spectra and azimuthal photon emission spectra are studied emphasizing the differences between pulsed and infinite laser fields. The proper description of the finite temporal duration of the laser pulse leads to a regularization of unphysical infinities (due to the infinite plane-wave description) of the laser-dressed Dirac-Volkov propagator and in the second-order strong-field process of two-photon Compton scattering. An enhancement of the two-photon process is found in strong laser pulses as compared to the corresponding weak-field process in perturbative QED.
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Bloch, Jacques Christophe Rodolphe. "Numerical investigation of fermion mass generation in QED." Thesis, Durham University, 1995. http://etheses.dur.ac.uk/5173/.
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We investigate the dynamical generation of fermion mass in quantum electrodynamics (QED). This non-perturbative study is performed using a truncated set of Schwinger-Dyson equations for the fermion and the photon propagator. First, we study dynamical fermion mass generation in quenched QED with the Curtis-Pennington vertex, which satisfies the Ward-Takahashi identity and moreover ensures the multiplicative renormalizability of the fermion propagator. We apply bifurcation analysis to determine the critical point for a general covariant gauge. In the second part of this work we investigate the dynamical generation of fermion mass in full, unquenched QED. We develop a numerical method to solve the system of three coupled non-linear equations for the dynamical fermion mass, the fermion wavefunction renormalization and the photon renormalization function. Much care is taken to ensure the high accuracy of the solutions. Moreover, we discuss in detail the proper numerical cancellation of the quadratic divergence in the vacuum polarization integral and the requirement of using smooth approximations to the solutions. To achieve this, we improve the numerical method by introducing the Chebyshev expansion method. We apply this method to the bare vertex approximation to unquenched QED to determine the critical coupling for a variety of approximations. This culminates in the detailed, highly accurate, solution of the Schwinger-Dyson equations for dynamical fermion mass generation in QED including both, the photon renormalization function and the fermion wavefunction renormalization in a consistent way, in the bare vertex approximation and, for the first time, using improved vertices. We introduce new improvements to the numerical method, to achieve the accuracy necessary to avoid unphysical quadratic divergences in the vacuum polarization with the Ball-Chiu vertex.
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Seymour-Smith, Nicolas R. "Ion-trap cavity QED system for probabilistic entanglement." Thesis, University of Sussex, 2012. http://sro.sussex.ac.uk/id/eprint/39687/.
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Laser systems and a linear radiofrequency (rf) Paul trap with an integrated co-axial cavity have been developed for experiments in cavity QED and probabilistic entanglement. Single 40Ca+ ions and large Coulomb crystals have been trapped routinely and laser cooled with long trapping lifetimes. A technique to achieve precise overlap of the pseudopotential minimum of the rf-field with the cavity mode has been implemented through variable capacitors in the resonant rf-circuit used to drive the trap. Three-dimensional micromotion compensation has been implemented. An 894 nm laser has been frequency stabilised to a Pound-Drever-Hall cavity which is in turn stabilised to atomic Cs using polarisation spectroscopy. The Allan variance of the error signal has been reduced to less than a kilohertz on timescales greater than a second. A novel implementation of the scanning cavity transfer lock has been developed to transfer the stability of the 894 nm laser to the 397 nm ion cooling and 866 nm repumping lasers. The bandwidth of the system has been increased to 380 Hz and the Allan variance of the error signal has been reduced to less than ten kilohertz on timescales of greater than a second. The pseudopotential minimum of the rf field has been overlapped optimally with the optical cavity mode through mapping of the fluorescence from cavity-field repumped ions as a function of their displacement. Coupling to the cavity mode has been confirmed by observation of resonant fluorescence into the cavity mode using the cavity-assisted Raman transition process. The thesis demonstrates that the setup is ready for the controlled production of single photons with pre-determined polarisation states, and progression onto new schemes to entangle multiple ions that are coupled to the optical cavity mode.
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Coles, Matthew. "A QED framework for nonlinear and singular optics." Thesis, University of East Anglia, 2014. https://ueaeprints.uea.ac.uk/48104/.
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The theory of quantum electrodynamics is employed in the description of linear and nonlinear optical effects. We study the effects of using a two energy level approximation in simplifying expressions obtained from perturbation theory, equivalent to truncating the completeness relation. However, applying a two-level model with a lack of regard for its domain of validity may deliver misleading results. A new theorem on the expectation values of analytical operator functions imposes additional constraints on any atom or molecule modelled as a two-level system. We introduce measures designed to indicate occasions when the two-level approximation may be valid. Analysis of the optical angular momentum operator delivers a division into spin and orbital parts satisfying electric-magnetic democracy, and determine a new compartmentalisation of the optical angular momentum. An analysis is performed on the recently rediscovered optical chirality, and its corresponding flux, delivering results proportional to the helicity and spin angular momentum in monochromatic beams. A new polarisation basis is introduced to determine the maximum values that an infinite family of optical helicity- and spin- type measures may take, and disproves recent claims of ‘superchiral light’. A theoretical description of recent experiments relate helicity- and spin- type measures to the circular differential response of molecules, and show that nodal enhancements to circular dichroism relate only to photon number-phase uncertainty relation and do not signify ‘superchiral’ regions. The six-wave mixing of optical vortex input, in nonlinear media, demonstrates the quantum entanglement of pairs of optical vortex modes. The probability for each possible output pair displays a combinatorial weighting, associated with Pascal’s triangle. A quantum electrodynamic analysis of the effect of a second body on absorption can be extended by integrating over all possible positions of the mediator molecules, modelling a continuous medium. This provides links with both the molecular and bulk properties of materials.
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Almeida, Luis Dias [UNESP]. "Quebra da simetria quiral na 'QED IND.3'." Universidade Estadual Paulista (UNESP), 1988. http://hdl.handle.net/11449/132518.
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Almeida, Luis Dias. "Quebra da simetria quiral na 'QED IND.3' /." São Paulo : [s.n.], 1988. http://hdl.handle.net/11449/132518.
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Zschocke, Sven. "Die Zwei-Photonen-Selbstenergie und andere QED-Strahlungskorrekturen." Forschungszentrum Rossendorf, 2001. https://hzdr.qucosa.de/id/qucosa%3A21790.
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Die genaue Messung der Lamb-Verschiebung stark gebundener Elektronen in Zusammenhang mit Tests der Quantenelektrodynamik (QED) in starken Feldern in hochgeladenen Ionen ist eines der Hauptthemen der heutigen Atomphysik. Die gegenwärtig durchgeführten Hochpräzisionsmessungen erfordern eine hohe Genauigkeit in den theoretischen Berechnungen der Lamb-Verschiebung. Diese Genauigkeit impliziert eine Berücksichtigung aller QED-Korrekturen der Ordnung α und α2, aber exakt in allen Ordnungen in Z&α. In den zurückliegenden Jahren sind die meisten dieser QED-Korrekturen sowohl in 1. Ordnung als auch in 2. Ordnung Störungstheorie berechnet worden. Der Beitrag der Zwei-Photonen-Selbstenergie konnte jedoch bisher nicht ausgewertet werden und stellte somit die größte Ungenauigkeit in der Vorhersage der Lamb-Verschiebung für wasserstoffartige Systeme dar. In dieser Arbeit wird der Beitrag dieser Prozesse zur Lamb-Verschiebung untersucht. Darüber hinaus werden erstmals renormierte Ausdrücke der Zwei-Photonen-Vakuumpolarisation und der Selbstenergie-Vakuumpolarisation hergeleitet. Bisher konnten diese Beträge nur in Uehling-Näherung ausgewertet werden.
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Luken, Jackson. "QED: A Fact Verification and Evidence Support System." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555074124008897.
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Everitt, Mark Stanley. "Construction, theory and simulation of cavity QED systems." Thesis, University of Leeds, 2009. http://etheses.whiterose.ac.uk/2786/.
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The microscopically pumped maser, or micromaser is a cavity QED experiment intended to be a physical realisation of the Jaynes-Cummings model of a single two-level atom interacting with a single mode electromagnetic field. This is the simplest model that describes the interaction between light and matter, yet it predicts behaviour unexpected from semiclassical models, such as the revival of Rabi oscillations of an atom interacting with an initially coherent field and non-monotonic linewidth as a function of pumping. The micromaser at the University of Leeds consists of a high quality superconducting microwave cavity designed to be resonant with the transition between two specific Rydberg states of rubidium. These two states behave like an ideal two level atom, and couple strongly to the cavity field due to a large dipole moment. These Rydberg atoms are passed through the cavity in a rarified beam such that in most instances when there is an atom in the cavity, there will only be one, closely approximating the Jaynes-Cummings model. I present experimental work on the build phase of the micromaser. Specifically I routed all of the wiring and microwave lines in the cryostat that contains the micromaser, and designed mounts for various components. I also designed several testing methods for probing high quality microwave cavity resonances and quality factors which are presented. Using the Jaynes-Cummings model as a prototype, I demonstrate how extensions to the model can be used to construct universal quantum logic gates that operate on photonic qubits in a multi-mode cavity. This could be realised in a micromaser with a multi-mode cavity. Conversely, I demonstrate that by using atoms as qubits, detuned cavities can be used to generate entangled resources such as the Greenberger-Horne-Zeilinger state, the W state, and graph states of atoms. I show that single qubit rotations on Rydberg atom qubits have already been experimentally demonstrated so that in combination these entangled resources are useful for quantum metrology, quantum computation and even tests of quantum gravity.
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Hannigan, Justin Michio 1977. "Hemispherical optical microcavity for cavity-QED strong coupling." Thesis, University of Oregon, 2009. http://hdl.handle.net/1794/10548.
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xv, 204 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.This thesis reports on progress made toward realizing strong cavity quantum electrodynamics coupling in a novel micro-cavity operating close to the hemispherical limit. Micro-cavities are ubiquitous wherever the aim is observing strong interactions in the low-energy limit. The cavity used in this work boasts a novel combination of properties. It utilizes a curved mirror with radius in the range of 40-60 µm that exhibits high reflectivity over a large solid angle and is capable of producing a diffraction limited mode waist in the approach to the hemispherical limit. This small waist implies a correspondingly small effective mode volume due to concentration of the field into a small transverse distance. The cavity assembled for this investigation possesses suitably low loss (suitably low linewidth) to observe vacuum Rabi splitting under suitable conditions. According to best estimates for the relevant system parameters, this system should be capable of displaying strong coupling. The dipole coupling strength, cavity loss and quantum dot dephasing rates are estimated to be, respectively, g = 35µeV, κ = 30µeV, and γ = 15µeV. A survey of two different distributed Bragg reflector (DBR) samples was carried out. Four different probe lasers were used to measure transmission spectra for the coupled cavity-QED system. The system initially failed to display strong coupling due to the available lasers being too far from the design wavelength of the spacer layer, corresponding to a loss of field strength at the location of the quantum dots. Unfortunately, the only available lasers capable of probing the design wavelength of the spacer layer had technical problems that prevented us from obtaining clean spectra. Both a Ti:Al 2 O 3 and a diode laser were used to measure transmission over the design wavelength range. The cavity used here has many promising features and should be capable of displaying strong coupling. It is believed that with a laser system centered at the design wavelength and possessing low enough linewidth and single-mode operation across a wide wavelength range strong coupling should be observable in this system.
Committee in charge: Hailin Wang, Chairperson, Physics; Michael Raymer, Advisor, Physics; Jens Noeckel, Member, Physics; Richard Taylor, Member, Physics; Andrew Marcus, Outside Member, Chemistry
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Clarke, David. "The Kapitza–Dirac Effect: An Approach from QED." Scholarship @ Claremont, 2003. https://scholarship.claremont.edu/hmc_theses/144.
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The Kapitza-Dirac effect is similar to the canonical experiment on diffraction of electrons through slits in an opaque screen, except that the diffraction grating has been replaced by a standing wave of light. Remarkably, incident electrons are diffracted by the standing light wave almost as if by a standard diffraction grating. Only recently has this effect been confirmed experimentally in this form [1], although it was originally predicted by Kapitza and Dirac almost 70 years ago. This paper examines the relativistic effects involved in this phenomena using the formalism of quantum field theory.
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Zverev, Nikolai. "Algorithmic studies of compact lattice QED with Wilson fermions." Doctoral thesis, [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963575082.
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Fortier, Kevin Michael. "Individual Trapped Atoms for Cavity QED Quantum Information Applications." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14625.
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To utilize a single atom as a quantum bit for a quantum computer requires exquisite
control over the internal and external degrees of freedom. This thesis develops techniques
for controlling the external degrees of freedom of individual atoms. In the first part of
this thesis, individual atoms are trapped and detected non-destructively by the addition of
cooling beams in an optical lattice. This non-destructive imaging technique led to atomic
storage times of two minutes in an optical lattice. The second part of thesis incorporated
the individual atoms into a high finesse cavity. Inside this optical cavity, atoms are cooled
and non-destructively observed for up to 10 seconds.
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Thoumany, Pierre. "Optical Spectroscopy and Cavity QED Experiments with Rydberg Atoms." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-130845.
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Linsefors, Linda. "Multi-photon emission in QED with strong background fields." Thesis, Umeå universitet, Institutionen för fysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-56265.
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In recent and upcoming years new lasers are being constructed withever higher intensity. These lasers open up the possibility of probingthe high intensity regime of particle physics, which will lead to etherconrming our current models in this regime or the discovery of beyondstandard model physics. However most previous theoretical results in thisarea are based old assumptions about the intensity and shape of the laserpulse that are no longer valid. In this thesis we calculate the tree-levelprobabilities for multi photon emission from an electron propagating inan arbitrary plane wave electromagnetic eld. We show that the classicallimit of our result agrees with the purely classical description of the sameevent. We calculate the soft emission correction to non-linear Comptonscattering. We conclude that our results are infrared divergent and arguethat this will be solved by including loop contributions to the process. Ourresults provide an important component for the theoretical predictions forthe outcome of scattering experiments in high intensity background eld.This thesis will add to the understanding of high intensity QED.