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Dissertations / Theses on the topic 'Lattice formulation of QCD'
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1
Ford, I. J. "Aspects of pure quantum chromodynamics on large lattices." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382631.
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Luz, Fernando Henrique e. Paula da. "Implementação do software MILC no estudo da QCD completa." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-23042010-081643/.
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A CromoDinâmica Quântica (QCD) é a teoria quântica de campos que descreve as interações fortes entre quarks, que são os constituintes fundamentais das partículas do núcleo atômico. Devido ao caráter peculiar destas interações, o estudo da QCD não pode ser realizado pelos métodos usuais em teorias quânticas de campos, baseados em expansões perturbativas. O estudo não-perturbativo da QCD a partir de primeiros princípios torna-se possível através da formulação de rede da teoria, que equivale a um modelo de mecânica estatística clássica, para o qual podem ser realizadas simulações numéricas através de métodos de Monte Carlo. A área de simulações numéricas da QCD representa uma das maiores aplicações atuais da computação de alto desempenho, sendo realizada nos principais centros computacionais do mundo. As grandes exigências do trabalho de pesquisa nesta área contribuíram inclusive para o desenvolvimento de novas arquiteturas computacionais. O uso de processamento paralelo é vital nessas simulações, principalmente nos casos em que está envolvida a simulação da chamada QCD completa, onde se consideram os efeitos dos quarks dinâmicos. Vários pacotes contendo implementações de algoritmos para o estudo da QCD começam a ser disponibilizados por grupos de pesquisa na área. Nosso foco neste trabalho é voltado para o pacote MILC. Além de fazer uma descrição detalhada da forma de utilização deste pacote, realizamos aqui um acompanhamento da evolução dos métodos empregados, desde o Método de Monte Carlo aplicado no algoritmo de Metropolis até a elaboração do algoritmo RHMC, introduzido recentemente. Fazemos uma comparação de e_ciência entre o RHMC e o algoritmo R, que foi o mais utilizado por décadas.Quantum ChromoDinamics (QCD) is the quantum field theory that describes the strong interactions between quarks, which are the fundamental constituents of particles in the atomic nucleus. Due to the peculiar characteristic of these interactions, the study of QCD cannot be carried out by usual methods in quantum field theory, which are based on pertubative expansions. The non-pertubative study of QCD from first principles becomes possible through the lattice formulation of the theory, which is equivalent to a classical statistical mechanics model, which in turn can be carried out by numerical simulations using Monte Carlo methods. The field of numerical simulations of QCD is one of the main applications of high performance computing, and is perfomed in most major computational centers around the world. The demanding requirements needed in this field led also to the development of new computational architectures. The use of parallel processing is vital in these types of simulations, especially in cases that involve what is known as full QCD, where the effects of dynamic quarks are taken into account. Several packages with algorithms implemented for the study of QCD have been recently made available by research groups in this field. The focus of this work is the MILC package. Here we make a detailed description of how to use this package and a follow up of the used methods, from the Monte Carlo method applied in the Metropolis algorithm up to the development of the RHMC algorithm, recently introduced. Comparisons are made between the e_ciency of RHMC and the R algorithm, which was the most used in the past decades.
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Serenone, Willian Matioli. "Potencial de quarks pesados com input de teorias de gauge na rede." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-24092014-163411/.
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Nesta dissertação nós revisamos aspectos gerais de teorias de gauge, os princípios da formulação de rede da cromodinâmica quântica (QCD) e algumas propriedades de quarkônios pesados, i.e. estados ligados de um quark pesado e seu antiquark. Como um exemplo de simulações de Monte Carlo de modelos de rede, apresentamos aplicações nos casos do oscilador harmônico e teorias de gauge SU(2). Nós estudamos o efeito de incorporar o propagador de gluon de simulações na rede em um modelo de potencial para a descrição do quarkônio, no caso do botômomio e do charmônio. Nós usamos em ambos os casos uma abordagem numérica para calcular as massas dos estados de quarkônio. O espectro resultante é comparado em ambos os casos com cálculos usando o potencial de Coulomb mais linear (ou potencial Cornell).In this dissertation we review general aspects of gauge theories, the principles of the lattice formulation of quantum chromodynamics (QCD) and some properties of heavy quarkonia, i.e. bound states of a heavy quark and its antiquark. As an illustration of Monte Carlo simulations of lattice models, we present applications in the case of the harmonic oscillator and SU(2) gauge theory. We study the effect of incorporating the gluon propagator from lattice simulations into a potential model for the description of quarkonium, in the case of bottomonium and charmonium. We use a numerical approach to evaluate masses of quarkonium states. The resulting spectrum is compared in both cases to calculations using the Coulomb plus linear (or Cornell) potential.
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Pickles, Stephen M. "Algorithms in lattice QCD." Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/11256.
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The enormous computing resources that large-scale simulations in Lattice QCD require will continue to test the limits of even the largest supercomputers into the foreseeable future. The efficiency of such simulations will therefore concern practitioners of lattice QCD for some time to come. I begin with an introduction to those aspects of lattice QCD essential to the remainder of the thesis, and follow with a description of the Wilson fermion matrix M, an object which is central to my theme. The principal bottleneck in Lattice QCD simulations is the solution of linear systems involving M, and this topic is treated in depth. I compare some of the more popular iterative methods, including Minimal Residual, Corij ugate Gradient on the Normal Equation, BI-Conjugate Gradient, QMR., BiCGSTAB and BiCGSTAB2, and then turn to a study of block algorithms, a special class of iterative solvers for systems with multiple right-hand sides. Included in this study are two block algorithms which had not previously been applied to lattice QCD. The next chapters are concerned with a generalised Hybrid Monte Carlo algorithm (OHM C) for QCD simulations involving dynamical quarks. I focus squarely on the efficient and robust implementation of GHMC, and describe some tricks to improve its performance. A limited set of results from HMC simulations at various parameter values is presented. A treatment of the non-hermitian Lanczos method and its application to the eigenvalue problem for M rounds off the theme of large-scale matrix computations.
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Skullerud, Jon Ivar. "Renormalisation in lattice QCD." Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/12965.
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This thesis investigates various aspects of the relation between the lattice and continuum formulations of quantum field theories, in particular QCD. The aim of this is to gain a better insight into the theory of QCD, and to be able to relate more accurately the numbers obtained from lattice simulations to experimental values for physical quantities. The first part of this thesis (chapters 1 and 2) gives a general introduction to quantum field theory, with emphasis on the lattice formulation of QCD. The first chapter describes the functional integral formulation of gauge theories and how it can be used to study these theories non-perturbatively by discretising the space-time variables. The second chapter discusses the principles behind the renormalisation of these theories. The Ward and Slavnov-Taylor identities that are preserved non-perturbatively, and can be invoked when renormalising the theory, are derived. The final part of this chapter discusses the renormalisation of composite operators, using both perturbative and non-perturbative methods. In particular, it is shown how the chiral Ward identities can be used to extract renormalisation constants for the axial and vector currents and the ratio of the scalar to the pseudoscalar density. In chapter 3, results for ZA, ZV and ZP/Zs at β = 6.2 are presented and their effects on calculations of physical quantities like decay constants are discussed. The final chapter investigates the quark-gluon vertex. The form factors of the off-shell vertex function, and the symmetries and Slavnov-Taylor identities that may be used to reduce these form factors, are discussed. I then outline a method for extracting the running coupling from the vertex function. This also includes a discussion of the quark and gluon field renormalisation.
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Simpson, Alan David. "Algorithms for lattice QCD." Thesis, University of Edinburgh, 1991. http://hdl.handle.net/1842/12946.
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Quantum Chromodynamics (QCD) is the present theory of the strong interactions between quarks and gluons. To simulate QCD on a computer we need to discretise the field theory onto a space-time lattice. After outlining the standard Wilson action for lattice QCD, we describe the improved Clover fermion action with reduced discretisation errors. This thesis describes various techniques required to simulate lattice QCD and their implementation on the UKQCD Grand Challenge supercomputer Maxwell, which is a parallel computer consisting of 64 nodes. The ideas behind Monte Carlo (MC) simulation are introduced through their use to study spin systems in statistical physics. Various MC algorithms are outlined with particular emphasis on Stochastic Cluster MC and attempts to apply this to lattice gauge simulations. One of the best quantities to calculate in lattice QCD is the quark propagator. This requires the inversion of very large fermion matrices and takes an enormous amount of supercomputer time. We investigate a simple Red-Black preconditioning of the matrix and compare the performance of an Over-relaxed Minimal Residual inversion algorithm with various Conjugate Gradient algorithms. The quark propagators are calculated using Maxwell and we give details of our implementation of the inversion routines and the performance obtained. We present preliminary results from an investigation into the hadron mass spectrum. These are based on a sample of 9 gauge configurations on a 243 x 48 lattice at β = 6.2. There are descriptions of how lattice masses are calculated and of Wuppertal smearing, which is a technique that may be used to improve the signal. We conclude with a comparison of the spectrum of masses obtained from the Wilson fermion action and the Clover action.
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Bonnet, Frédéric D. R. "Improved actions in lattice QCD /." Title page, contents and introduction only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09phb717.pdf.
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McCallum, Paul. "Upsilon spectroscopy using lattice QCD." Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363170.
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Johnson, Christopher Andrew. "Fermion determinants in lattice QCD." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250410.
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Campbell, N. A. "Static potentials in lattice QCD." Thesis, University of Liverpool, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377123.
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Burford, Darren Ross. "Hadronic physics in lattice QCD." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242536.
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Gambhir, Arjun Singh. "Disconnected Diagrams in Lattice Qcd." W&M ScholarWorks, 2017. https://scholarworks.wm.edu/etd/1516639772.
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In this work, we present state-of-the-art numerical methods and their applications for computing a particular class of observables using lattice quantum chromodynamics (Lattice QCD), a discretized version of the fundamental theory of quarks and gluons. These observables require calculating so called "disconnected diagrams" and are important for understanding many aspects of hadron structure, such as the strange content of the proton. We begin by introducing the reader to the key concepts of Lattice QCD and rigorously define the meaning of disconnected diagrams through an example of the Wick contractions of the nucleon. Subsequently, the calculation of observables requiring disconnected diagrams is posed as the computationally challenging problem of finding the trace of the inverse of an incredibly large, sparse matrix. This is followed by a brief primer of numerical sparse matrix techniques that overviews broadly used methods in Lattice QCD and builds the background for the novel algorithm presented in this work. We then introduce singular value deflation as a method to improve convergence of trace estimation and analyze its effects on matrices from a variety of fields, including chemical transport modeling, magnetohydrodynamics, and QCD. Finally, we apply this method to compute observables such as the strange axial charge of the proton and strange sigma terms in light nuclei. The work in this thesis is innovative for four reasons. First, we analyze the effects of deflation with a model that makes qualitative predictions about its effectiveness, taking only the singular value spectrum as input, and compare deflated variance with different types of trace estimator noise. Second, the synergy between probing methods and deflation is investigated both experimentally and theoretically. Third, we use the synergistic combination of deflation and a graph coloring algorithm known as hierarchical probing to conduct a lattice calculation of light disconnected matrix elements of the nucleon at two different values of the lattice spacing. Finally, we employ these algorithms to do a high-precision study of strange sigma terms in light nuclei; to our knowledge this is the first calculation of its kind from Lattice QCD.
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Dinter, Simon. "Nucleon structure from lattice QCD." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2012. http://dx.doi.org/10.18452/16629.
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In dieser Arbeit berechnen wir mit Hilfe der Gitter-QCD Observablen, die in Beziehung zur Struktur des Nukleons stehen. Ein Teil dieser Arbeit beschäftigt sich mit Momenten von Parton-Verteilungsfunktionen. Solche Momente sind wichtig für das Verständnis der Nukleon-Struktur und werden durch globale Analysen von tief-inelastischen Streuexperimenten bestimmt. Eine theoretische, nicht-perturbative Rechnung der Momente in der Gitter-QCD ist möglich. Allerdings existiert, seit solche Gitter-QCD Rechnungen vorliegen, eine Diskrepanz zwischen diesen Rechnungen und den Ergebnissen globaler Analysen experimenteller Daten. Wir untersuchen, ob systematische Effekte für diese Diskrepanz verantwortlich sind, dabei studieren wir insbesondere die Effekte angeregter Zustände. Zudem führen wir eine erste Rechnung mit vier dynamischen Quark-Flavors durch. Ein weiterer Aspekt dieser Arbeit ist eine Machbarkeitsstudie zur Berechnung des skalaren Quark-Inhalts des Nukleons in der Gitter-QCD. Dieser bestimmt den Wirkungsquerschnitt der durch ein skalares Teilchen (z.B. ein Higgs-Teilchen) vermittelten Wechselwirkung eines schweren Teilchens mit einem Nukleon und kann somit einen Einfluss bei der Suche nach Dunkler Materie haben. Bisherige Gitter-Rechnungen dieser Größe besitzen große Unsicherheiten und sind daher von geringer Signifikanz für phenomenologische Anwendungen. Wir benutzen eine Varianz-Reduktions-Methode zur Auswertung von unverbundenen Diagrammen um ein präzises Ergebnis zu erhalten. Des Weiteren stellen wir eine neue stochastische Methode zur Berechnung von Nukleon-Dreipunkt-Korrelationsfunktionen vor, die für die Berechnung von Observablen der Nukleon-Struktur benötigt werden. Wir testen die Konkurrenzfähigkeit dieser neuen Methode gegenüber der Standard-Methode. In allen Rechnungen benutzen wir Wilson twisted-Mass Fermionen mit maximalem Twist, so dass die hier berechneten Observablen nur O(a^2) Diskretisierungsfehler aufweisen.In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a^2) discretization effects.
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Fukaya, Hidenori. "Lattice QCD with fixed topology." 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/144178.
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Kyoto University (京都大学)0048
新制・課程博士
博士(理学)
甲第12095号
理博第2989号
新制||理||1446(附属図書館)
23931
UT51-2006-J90
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 大野木 哲也, 教授 二宮 正夫, 教授 畑 浩之
学位規則第4条第1項該当
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Roweth, Duncan. "Parallel algorithms for lattice QCD." Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/12886.
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Warkentin, Nikolaus. "Nucleon wave function from lattice QCD." kostenfrei, 2008. http://www.opus-bayern.de/uni-regensburg/volltexte/2008/1006/.
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Kendall, Iain D. "Lattice QCD studies of Upsilon physics." Thesis, University of Glasgow, 2010. http://theses.gla.ac.uk/2280/.
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Non-Relativistic QCD (henceforth NRQCD) is a non-relativistic effective theory that models the strong interaction. We use this formulation to perform lattice simulations of the bound states of b quarks, known as the Upsilon spectrum. These simulations are performed on a range of gauge ensembles provided by the MILC collaboration that include three flavours of quark content - one at the approximate mass of the strange quark, and two degenerate flavours that range from about a half to a tenth of the mass of the strange quark. We implement a random wall algorithm in the creation of our b quark propagators, and develop a technique to combine the random wall with smearing functions, which are used to assist in picking out the relevant quantum numbers in the the resulting meson correlator. This is the first time these techniques have been used in this manner. We employ a Bayesian fitting procedure to extract energies and amplitudes from our simulated correlators. By using the 2S−1S Upsilon splitting on each configuration, and matching to experimental results, we are able to extract the lattice spacings for each ensemble from which we determine the heavy quark potential scale parameter r1. In concert with results from our collaborators, we outline the procedure for combining multiple determinations of r1, and present the collaborative result. We then use this parameter in a determination of the strong coupling constant αs in the MS scheme. We investigate the dispersion relation of the NRQCD action, and note some undesirable features that we are able to resolve with the precision attainable using the random wall. We look at a number of ways to address these issues, including non-perturbative and perturbative tuning of coefficients. Using the perturbative coefficients, we then proceed to calculate heavy-heavy currents, which are perturbatively matched to the continuum, and allow us to give results for the Upsilon leptonic width.
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Stella, Nicoletta. "Heavy baryon phenomenology from lattice QCD." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242393.
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Hill, Victor John. "Heavy flavour physics from lattice QCD." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252696.
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Heatlie, Grant James. "Aspects of phenomenology from lattice QCD." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303058.
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Bär, Oliver. "Chiral perturbation theory for lattice QCD." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/13976.
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Eine zusammenfassende Übersicht über die Formulierung der chiralen Störungstheorie (ChPT) für die Gitter Quantenchromodynamik (QCD) ist gegeben. Wir beginnen mit kurzen Zusammenfassungen der chiralen Störungstheorie für die Kontinuum-QCD sowie Symanziks effektiver Theorie für die Gitter-QCD. Anschließend wird die Formulierung der ChPT für die Gitter-QCD behandelt. Nach einem weiteren Kapitel über partial quenching und Theorien mit gemischten Wirkungen werden konkrete Anwendungen diskutiert: Wilson ChPT, staggered ChPT sowie Wilson ChPT mit einem chiral verdrehten Massenterm. Die folgenden Kapitel behandeln das Epsilonregime mit Wilsonfermionen sowie ausgewählte Resultate für ChPT mit gemischten Wirkungen. Den Abschluß bildet die Formulierung der chiralen Störungstheorie für schwere Vektormesonen mit Wilsonfermionen.The formulation of chiral perturbation theory (ChPT) for lattice Quantum Chromodynamics (QCD) is reviewed. We start with brief summaries of ChPT for continuum QCD as well as the Symanzik effective theory for lattice QCD. We then review the formulation of ChPT for lattice QCD. After an additional chapter on partial quenching and mixed action theories various concrete applications are discussed: Wilson ChPT, staggered ChPT and Wilson ChPT with a twisted mass term. The remaining chapters deal with the epsilon regime with Wilson fermions and selected results in mixed action ChPT. Finally, the formulation of heavy vector meson ChPT with Wilson fermions is discussed.
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Renner, Dru Bryant 1977. "Exploring proton structure using lattice QCD." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/29448.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.Includes bibliographical references (leaves 219-222).
We calculate moments of the generalized parton distributions of the nucleon using lattice QCD. The generalized parton distributions determine the angular momentum decomposition of the nucleon and the transverse distributions of partons within the nucleon. Additionally, the generalized parton distributions reduce to the elastic form factors and ordinary parton distributions in particular kinematic limits. Thus by calculating moments of the generalized parton distributions in lattice QCD we can explore many facets of the structure of the nucleon. In this effort, we have developed the building block method to determine all the lattice correlation functions which con- tribute to the off forward matrix elements of the twist two operators. These matrix elements determine the generalized form factors of the nucleon which in turn give the moments of the generalized parton distributions. Thus we use our building block method to calculate all the matrix elements of the lowest twist two operators. Fur- thermore, we use our method to construct an overdetermined set of matrix elements allowing a more accurate calculation of the generalized form factors.
by Dru Bryant Renner.
Ph.D.
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Janowski, Tadeusz. "Hadronic kaon decays from lattice QCD." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/386224/.
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Nakano, Takashi. "Strong-coupling Analysis of Lattice QCD." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/175119.
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Garden, Joyce. "Light hadron spectroscopy in lattice QCD." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/14886.
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This thesis presents the results of a numerical calculation of the light hadron spectrum in the lattice formulation of Quantum Chromodynamics. Results were obtained in both the quenched approximation, where the effects of quark loops in the QCD vacuum were neglected, and in "full" QCD, where two degenerate flavours of dynamical fermions were included in the simulation. All numerical simulations employed the standard Wilson gauge action with an O(a) improved Wilson fermion action. This study confirms that the quenched light hadron mass spectrum agrees with experiment at the 10% level. Finite size effects at one value of the coupling were investigated and an improved scaling behaviour arising from the implementation of the O(a) improvement programme was observed for the quenched simulations. With the aim of observing effects in the spectrum due to the inclusion of fermion loops in the QCD vacuum, simulations in "full" QCD forming a matched ensemble were compared with a quenched simulation at the same lattice spacing. Each simulation in the method ensemble was selected to have approximately the same lattice spacing as defined with respect to a physical observable in order to investigate chiral extrapolations independently from continuum extrapolations. A further simulation with a lighter sea quark mass at a smaller lattice spacing was included in the analysis for comparison. Evidence for small yet significant dynamical effects arising from the comparison with the quenched data were observed in the hyperfine splitting and partially quenched chiral extrapolations. Results obtained from the matched ensemble displayed a reduced residual dependence upon lattice artifacts.
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Sternbeck, André. "The infrared behavior of lattice QCD green's functions a numerical study of lattice QCD in Landau gauge /." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981291910.
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Cooney, Paul. "Proton decay matrix elements from lattice QCD." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4042.
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We present results for the matrix elements relevant for proton decay in Grand Unified Theories (GUTs), using two methods. In the indirect method, we rely on an effective field theory description of proton decay, where we need to estimate two low energy constants. We then relate these low energy constants to the proton decay matrix elements using leading order chiral perturbation theory. In the direct method, we calculate the required matrix elements directly; this is computationally more expensive, but the calculation has no systematic error from the use of chiral perturbation theory. The calculations are performed with 2+1 flavors of domain wall fermions on lattices of size 163 × 32 and 243 × 64 with a fifth dimension of length 16. We work at fixed inverse lattice spacing, a−1 = 1.73(3) GeV, leading to physical volumes of (1.8 fm)3 and (2.7 fm)3 for the 163 × 32 and 243 × 64 lattices respectively. In the first four chapters we present the background theory. We start with a brief review of the standard model and the motivation for GUTs. We show that GUTs must lead to proton decay, and that the proton lifetime is an experimentally testable prediction which can be used to constrain GUT parameters, or rule out classes of GUT which predict a minimum lifetime shorter than the experimental minimum bound. We then review continuum and lattice QCD, including outlines of the lattice methods used to calculate the proton decay matrix elements. In the last three chapters we present the results and analysis. We calculate the nucleon and pion two–point correlation functions, and determine their ground state masses and amplitudes. These quantities will then be used to calculate the matrix elements using the indirect and direct methods outlined above. The matrix elements can then be combined with experimental bounds on the proton lifetime to bound parameters of individual GUTs.
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Ivanenko, Taras. "Study of instanton physics in lattice QCD." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/28176.
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Lepzelter, David 1981. "Use of correlation matrices in lattice QCD." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32742.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.Includes bibliographical references (p. 117).
This thesis explores the use of correlation matrices in analyzing Monte Carlo calculations from lattice quantum chromodynamics. Correlation matrices are a powerful tool for examining many problems in which significant correlations exist, and thus offer potential advantages for lattice QCD. Several models were used to study the relative advantages of correlated and uncorrelated analyses. However, when applied to actual lattice data at current statistics, the method appears to be undesirably biased.
by David Lepzelter.
S.B.
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Rios, Tascon Andres. "Exploration of new methods for Lattice QCD." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111884.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 59-60).
We explore two methods aimed at alleviating two difficulties in Lattice QCD: statistical noise and data storage. The first method intends to improve the signal-to-noise (S/N) ratio in three-point correlators, by extending previous work by Detmold and Endres. We test the method in the measurement of two observables: the nucleonic axial charge, and a matrix element computation related to the electromagnetic form factor of the rho meson. Only in the case of the rho we see a very slight improvement. We conclude that, in general, a case-by-case study would be needed to determine the effectiveness of the S/N optimization. The second method that we study aims to improve data compression of gauge fields. It consists in generating a set of matrices distributed roughly uniformly along the group manifold, and constructing fine lattices around each of these matrices. We show that this compression can indeed provide better performance for SU(2) and SU(3) than the Lie algebra compression, but the improvement is not very significant. Nevertheless, we show that it is fairly close to the best compression one could hope to achieve with this type of method. We find that the compression procedure is very costly, which makes it currently impractical for machine precision- compression. We conclude that studies must be done to determine if it can be improved by using additional information from the gauge fields.
by Andres Rios Tascon.
S.B.
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Bailas, Gabriela. "Aspects of charmonium physics in Lattice QCD." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAC025/document.
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Les états de charmonium fournissent une source de connaissances pertinente pour déterminer les paramètres fondamentaux du Modèle Standard. Un aspect important de la compréhension et des tests de la QCD est de faire des prédictions précises du spectre des hadrons et de les tester par rapport à des données expérimentales de haute qualité. Notre cadre théorique est Lattice QCD, qui est considéré comme le seul moyen connu de traiter le lagrangien QCD complet de manière non perturbative et bien adaptée au calcul numérique. En utilisant l'action Wilson-Clover avec N_f = 2 saveurs dynamiques, nous étudierons les deux mésons charmonium eta_c et J/\psi. Nous allons également étudier certaines propriétés de leur première excitation radiale eta_c (2S) et \psi(2S)Charmonium states provide a relevant source of knowledge for determining fundamental parameters of the Standard Model. An important aspect of understanding Quantum ChromoDynamics (QCD) is to make precise predictions of the hadron spectrum and to test them against high-quality experimental data. Our theoretical framework is Lattice QCD, which is considered to be the only known way to treat the full QCD Lagrangian non perturbatively from first principles, in a manner well suited to numerical computation. By using the Wilson-Clover action with N_f = 2 dynamical flavors, we will study the two charmonium mesons eta_c and J/\psi. We will also investigate some properties of their first radial excitations eta_c(2S) and psi(2S)
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Joo, Balint. "Efficient Monte Carlo simulation of Lattice QCD." Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/12319.
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This thesis is concerned with the efficient simulation of lattice QCD with dynamical fermions. We discuss two aspects of this theme, the tuning of existing algorithms and the investigation of novel algorithms. We begin with an introduction to lattice QCD and Monte Carlo Methods for its simulation. Particular emphasis is placed on the difficulties of the lattice formulation of fermion fields. We then continue with a description of the Hybrid Monte Carlo (HMC) algorithm, focusing on the conditions the algorithm must obey for correctness and on some of the numerical methods required for its implementation. We then discuss issues of reversibility and instability for the Molecular Dynamics part of HMC algorithm. After considering the source of instabilities in the context of free field theory we adopt a working hypothesis by which we can relate this instability to the case of lattice QCD. Our tuning studies of HMC attempt to investigate the behaviour of reversibility violations and simulation cost in the molecular dynamics with varying solver target residue r. We also investigate the onset of instabilities in the molecular dynamics while varying the solver residue r and the stepsize dt. Our second subject is the investigation of novel simulation algorithms. We consider the Parallel Tempering (PT) algorithm and its application to lattice QCD. We give an introduction to the algorithm and discuss the use of action matching technologies to tune the simulation parameters for maximal swap acceptance rates. We then discuss issues of cost for PT simulations by considering the CPU time needed by the algorithm for the estimation of the expectation value of an observable of interest and comparing this with the cost of reference HMC simulations. Finally we present some numerical results which indicate that we have a reasonable understanding of the algorithm but that we have not managed to maximise the acceptance rate through action matching. Due to large errors on our measured autocorrelation time we reserve judgements on the question of cost efficiency of the algorithm.
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Sroczynski, Zbigniew. "Taking lattice QCD beyond the quenched approximation." Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/14472.
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This thesis is mainly concerned with the problem of generating gauge configurations for use in Monte-Carlo lattice QCD calculations that include the effects of dynamical fermions. Although algorithms to do this have been in existence for some time the computing power necessary for their application at a scale where physically relevant results can be obtained has only recently become available, so these large scale dynamical simulations are still a new feature of lattice QCD. The emphasis here is on the new experiences gained from the design, implementation and development of a particular dynamical gauge configuration algorithm, and from its initial use in production. The intention is that this will facilitate future computations where the effects of dynamical fermions in QCD can be systematically explored, and the further development of better algorithmic techniques. The first chapter outlines those features of lattice gauge theory computations that are salient to this work, concentrating particularly on the motivations for and consequences of going beyond the quenched approximation and on the properties of Markov processes used in the generation of gauge configurations. The second chapter introduces the main types of algorithm employed for dynamical gauge configuration production, viz. the multiboson algorithm and Hybrid Monte-Carlo, and explains how they work. In chapter 3 the implementation of the chosen algorithm (Generalised Hybrid Monte-Carlo) is described, along with various algorithmic investigations, coding developments, performance evaluation, and a description of the procedures used in the verification of the code. Finally, some results are presented from the first large scale production runs on the Cray-TBE which attempt to put the algorithm work into a physical context.
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Mazur, Lukas [Verfasser]. "Topological Aspects in Lattice QCD / Lukas Mazur." Bielefeld : Universitätsbibliothek Bielefeld, 2021. http://d-nb.info/1240832443/34.
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Ichihara, Terukazu. "Fluctuations in QCD phase diagram in the strong coupling limit of lattice QCD." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215301.
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権利表示を行うこと, 出典表示を行うこと, 出版社版へのリンクを表示することKyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第19488号
理博第4148号
新制||理||1596(附属図書館)
32524
京都大学大学院理学研究科物理学・宇宙物理学専攻
(主査)教授 大西 明, 准教授 菅沼 秀夫, 教授 田中 貴浩
学位規則第4条第1項該当
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Schulze, Robert. "From hot lattice QCD to cold quark stars." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-65426.
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A thermodynamic model of the quark-gluon plasma using quasiparticle degrees of freedom based on the hard thermal loop self-energies is introduced. It provides a connection between an established phenomenological quasiparticle model – following from the former using a series of approximations – and QCD – from which the former is derived using the Cornwall-Jackiw-Tomboulis formalism and a special parametrization of the running coupling.
Both models allow for an extrapolation of first-principle QCD results available at small chemical potentials using Monte-Carlo methods on the lattice to large net baryon densities with remarkably similar results. They are used to construct equations of state for heavy-ion collider experiments at SPS and FAIR as well as quark and neutron star interiors. A mixed-phase construction allows for a connection of the SPS equation of state to the hadron resonance gas.
An extension to the weak sector is presented as well as general stability and binding arguments for compact stellar objects are developed. From the extrapolation of the most recent lattice results [Baz09, Bor10b] the existence of bound pure quark stars is not suggested. However, quark matter might exist in a hybrid phase in cores of neutron stars.
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Jäger, Benjamin [Verfasser]. "Hadronic matrix elements in lattice QCD / Benjamin Jäger." Mainz : Universitätsbibliothek Mainz, 2014. http://d-nb.info/1051121140/34.
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Thaler, Michael. "Phases of QCD lattice thermodynamics and quasiparticle approaches /." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=978932617.
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Kahl, Karsten. "Adaptive Algebraic Multigrid Methods for Lattice QCD Computations." Wuppertal Universitätsbibliothek Wuppertal, 2010. http://d-nb.info/1000531767/34.
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Ehmann, Christian. "A lattice QCD calculation of the charmonium spectrum." Regensburg Univ.-Verl. Regensburg, 2010. http://d-nb.info/1003055079/04.
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Van, de Water Ruth S. "Applications of chiral perturbation theory to lattice QCD /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/9730.
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Stewart, Chris. "Strings, quarkonium and nuclear physics in lattice QCD." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ56269.pdf.
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Engelson, Eric. "Excited nucleon and delta spectra from lattice QCD." College Park, Md.: University of Maryland, 2009. http://hdl.handle.net/1903/9564.
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Thesis (Ph.D.) -- University of Maryland, College Park, 2009.Thesis research directed by: Dept. of 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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Allison, Ian. "Dynamical lattice QCD determinations for heavy quark physics." Thesis, University of Glasgow, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425153.
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Lesk, Victor Isaac. "Heavy-light hadron matrix elements from lattice QCD." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323943.
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Gough, Bran James. "Calculation of rare B decays in lattice QCD." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241262.
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Brantley, David. "Applications of Lattice Qcd to Hadronic Cp Violation." W&M ScholarWorks, 2018. https://scholarworks.wm.edu/etd/1550153870.
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Experimental tests of the Standard Model are reaching a precision in which they are probing beyond Standard Model parameter spaces. Increasingly precise experimental tests of the Standard Model (SM) require a concurrent theoretical push to provide ever more precise predictions to interpret experimental results. For example, future direct dark matter detection experiments, searches for Majorana neutrinos, and neutron electric dipole moment searches, all require a fundamental understanding of nuclear physics in the low-energy regime. Nuclear physics emerges from non-perturbative dynamics of the fundamental theory of the strong interaction, QCD, at low energies. Lattice QCD is currently our only systematically controllable solution to QCD in the low-energy regime, and coupled with effective field theory, can be used to provide precise physical predictions from QCD. in this thesis, we focused on lattice calculations which have implications for precision tests of the Standard Model. After a brief introduction to lattice QCD and EFT, we present a lattice computation of the strong isospin breaking contribution to the neutron-proton and cascade mass splitting. We observe non-analytic behavior in the neutron-proton and cascade mass splittings, which is uniquely indicative of chiral dynamics. The neutron-proton mass splitting is related via chiral symmetry to the CP-violating pion-nucleon interactions induced by the QCD θ-term, and we provide an estimate of the induced pion-nucleon coupling arising from the θ-term. in the next section, we present the first calculation of the renormalization factors for bilinear operators, and the four quark operator basis induced by new physics, which were computed on the Möbius Domain Wall fermion on gradient flowed HISQ ensembles. We use momentum sources and the RI-SMOM method, using two projection schemes, and use the step scaling procedure to calculate the running of our operators up to a scale of 3 GeV. in chapter 5, we presented progress in the first lattice QCD calculation of the CP-violating pion-nucleon couplings induced by the quark chromo-electric dipole operators. These long-range pion-nucleon interactions lead to an enhanced nuclear Schiff moment in diamagnetic atoms, and thus play an important role in the interpretation of nuclear EDM experiments. in this work, we use chiral perturbation theory, as well as an unconventional method of calculating nucleon matrix elements on the lattice, to calculate the bare couplings in terms of spectroscopic shifts of the nucleon mass induced by the CP-conserving quark chromo-magnetic dipole operators. We then detail the renormalization procedure to be used to renormalize the chromo-magnetic operator, including subtraction of the power divergent mixing with the scalar operator.
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Sternbeck, André. "The infrared behavior of lattice QCD green's functions." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2006. http://dx.doi.org/10.18452/15527.
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Diese Arbeit untersucht im Rahmen der Gittereichtheorie verschiedene Aspekte der QCD in der Landau-Eichung, insbesondere solche, die mit den Gluon- und Geist-Propagatoren bei kleinen Impulsen zusammenhängen. Die Eichgruppe ist SU(3). Wir analysieren den Einfluss unterschiedlicher systematischer Effekte. Wir zeigen, dass der Formfaktor des Geist-Propagators bei kleinen Impulsen systematisch von der Wahl der Eichkopien (Gribov-Kopien) abhängt. Hingegen können wir einen solchen Einfluss auf den Gluon-Propagator nicht feststellen. Ebenfalls wird die Verteilung der kleinsten Eigenwerte des Faddeev-Popov-Operators durch die Wahl der Eichkopien beeinflusst. Wir zeigen außerdem, dass der Einfluss dynamischer Wilson-Fermionen auf den Geist-Propagator für die untersuchten Impulse vernachlässigbar ist. Für den Gluon-Propagator können wir jedoch einen deutlichen Einfluss für große und mittlere Impulse feststellen. Zusätzlich wurden beide Propagatoren auf asymmetrischen Gittern gemessen und mit den Daten von symmetrischen Gittern verglichen. Wir vergleichen unsere Ergebnisse mit denen aus Studien von Dyson-Schwinger-Gleichungen für den Gluon- und Geist-Propagator. Wir zeigen, dass das in dieser Arbeit gefundene Niedrigimpulsverhalten im Einklang mit verschiedenen Kriterien für Confinement (Einschluss von Farbladungen) ist. Wir berechnen die laufende Kopplung, die sich als eine renormierungsgruppeninvariante Kombination der Gluon- und Geist-Formfaktoren ergibt. Unsere Ergebnisse zeigen, dass im Bereich kleiner Impulse die laufende Kopplung kleiner wird und so vermutlich kein endlicher Infrarot-Fixpunkt im Grenzfall Impuls Null angestrebt wird. Wir präsentieren außerdem eine erste nichtstörungstheoretische Berechnung der Renormierungskonstante des SU(3) Ghost-Gluon-Vertex. Wir berichten über Untersuchungen zu spektralen Eigenschaften des Faddeev-Popov-Operators. Dazu haben wir eine Reihe der kleinsten Eigenwerte und Eigenvektoren dieses Operators berechnet.Within the framework of lattice QCD we investigate different aspects of QCD in Landau gauge using Monte Carlo simulations. In particular, we focus on the low momentum behavior of gluon and ghost propagators. The gauge group is SU(3). Different systematic effects on the gluon and ghost propagators are studied. We demonstrate the ghost dressing function to systematically depend on the choice of Gribov copies at low momentum, while the influence on the gluon dressing function is not resolvable. Also the eigenvalue distribution of the Faddeev-Popov operator is sensitive to Gribov copies. We show that the influence of dynamical Wilson fermions on the ghost propagator is negligible at the momenta available to us. On the contrary, fermions affect the gluon propagator at large and intermediate momenta. In addition, we analyze data for both propagators obtained on asymmetric lattices and compare these results with data obtained on symmetric lattices. We compare our data with results from studies of Dyson-Schwinger equations for the gluon and ghost propagators. We demonstrate that the infrared behavior of both propagators, as found in this thesis, is consistent with different criteria for confinement. However, the running coupling constant, given as a renormalization-group-invariant combination of the gluon and ghost dressing functions, does not expose a finite infrared fixed point. Rather the data are in favor of an infrared vanishing coupling constant. We also report on a first nonperturbative computation of the SU(3) ghost-gluon-vertex renormalization constant. We present results of an investigation of the spectral properties of the Faddeev-Popov operator. For this we have calculated the low-lying eigenvalues and eigenmodes of the Faddeev-Popov operator.
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Guazzini, Damiano. "Heavy-light mesons in lattice HQET and QCD." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2007. http://dx.doi.org/10.18452/15713.
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Wir stellen eine Untersuchung einer Kombination zwischen HQET und relativistischer QCD vor, die das Ziel hat, die b-Quark Masse und die Zerfallskonstante des Bs-Mesons aus Gitter-Simulationen, unter Nichtbeachtung virtueller Fermionenschleifen, zu gewinnen. Wir beginnen mit einem kleinen Volumen, in dem man das b-Quark direkt simulieren kann, und stellen die numerische Verbindung mit einem großen Volumen, wo ``finite-size'''' Effekte vernachlässigbar sind, mit Hilfe einer ``finite-size'''' Methode her. Diese besteht aus zum Kontinuum extrapolierten Schritten, wobei der Massenpunkt, der der physikalischen b-Quark Masse entspricht, durch eine Interpolation erreicht wird. In diese Interpolation fliessen die in der HQET erzielten Resultate ein. Mit dem durch die Sommersche Skale r0 bestimmten Gitterabstand und den experimentalen Werten für die Bs- und K-Massen erhalten wir die Endergebnisse für die renormierungsgruppeninvariante Masse Mb = 6.88(10) GeV, äquivalent zu mb(mb) = 4.42(6) GeV in dem MSbar-Schema und fBs = 191(6) MeV für die Zerfallskonstante. Eine Renormierungsbedingung für den Chromo-magnetischen Operator, der in führender Ordnung der Entwicklung in der schweren Quarkmasse in HQET für die Massenaufspaltung zwischen dem pseudoskalaren und dem vektoriellen Kanal mesonischer schwer-leicht gebundener Zustände verantwortlich ist, wird auf der Basis von Gitter-Korrelationsfunktionen bereitgestellt. Dies eignet sich gut für eine nicht-störungstheoretische Rechnung, welche einen großen Bereich der Renormierungsskala umfasst und keine Valenz-Quarks beinhaltet. Die Zwei-Schleifen Ordnung der entsprechenden anomalen Dimension im Schrödinger-Funktional-Schema wird mit Hilfe von veröffentlichten Ergebnissen berechnet; dies erforderte eine neue Ein-Schleifen Rechnung im SF-Schema mit einem nicht verschwindenden Hintergrundfeld. Die Gitterartefakte bezüglich der Skalenentwicklung des Renormierungsfaktors werden zur Ein-Schleifen Ordnung untersucht, und es wird von nicht-störungstheoretischen Simulationen, unter Nichtbeachtung virtueller Fermionenschleifen, bestätigt, dass sie für die gegenwärtige verfügbare numerische Präzision vernachlässigbar sind.We present a study of a combination of HQET and relativistic QCD to extract the b-quark mass and the Bs-meson decay constant from lattice quenched simulations. We start from a small volume, where one can directly simulate the b-quark, and compute the connection to a large volume, where finite size effects are negligible, through a finite size technique. The latter consists of steps extrapolated to the continuum limit, where the b-region is reached through interpolations guided by the effective theory. With the lattice spacing given in terms of the Sommer''s scale r0 and the experimental Bs and K masses, we get the final results for the renormalization group invariant mass Mb = 6.88(10) GeV, translating into mb(mb) = 4.42(6) GeV in the MSbar scheme, and fBs = 191(6) MeV for the decay constant. A renormalization condition for the chromo-magnetic operator, responsible, at leading order in the heavy quark mass expansion of HQET, for the mass splitting between the pseudoscalar and the vector channel in mesonic heavy-light bound states, is provided in terms of lattice correlations functions which well suits a non-perturbative computation involving a large range of renormalization scales and no valence quarks. The two-loop expression of the corresponding anomalous dimension in the Schrödinger functional (SF) scheme is computed starting from results in the literature; it requires a one-loop calculation in the SF scheme with a non-vanishing background field. The cutoff effects affecting the scale evolution of the renormalization factors are studied at one-loop order, and confirmed by non-perturbative quenched computations to be negligible for the numerical precision achievable at present.
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Cheung, Gavin. "Spectroscopy of exotic charm mesons from lattice QCD." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/285556.
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Exotic mesons are mesons that cannot be described as a quark-antiquark pair. The number of exotic mesons has been growing every year in the charm sector and the theoretical understanding of them is often conflicted amongst the community. Some possible explanations include hybrid mesons where the quark-antiquark pair is coupled to a gluonic excitation, compact tetraquarks where four quarks are bound into a localised state and molecules which consist of pairs of extended mesons. To study exotic mesons from first principles, lattice QCD provides the framework to perform spectroscopy calculations numerically. I will give a review and describe the relevant techniques used in this thesis. After doing so, I will calculate masses of charmonium with angular momentum up to four. The results show QCD permits states with exotic quantum numbers that are not accessible by a quark-antiquark pair. I will identify states that are consistent with the quark-antiquark picture and then show that the remaining states in the extracted spectra can be interpreted to be the lightest and first excited hybrid meson supermultiplet. Whilst the mass is one quantity that can be computed, hadron spectroscopy is also concerned with the calculation of the unstable properties of resonances which can decay into meson-meson states. These meson-meson states have four quarks and could also mix with tetraquarks. I will describe how to correctly extract the energies of four quark states within lattice QCD by reviewing operators resembling meson-mesons and then constructing a general class of operators resembling tetraquarks. I will then calculate a variety of spectra in the isospin-1 hidden charm sector and the doubly charmed sector. No evidence of a bound state or narrow resonance is found in these channels. Having described how to include multi-meson states in lattice QCD, I will describe how to relate the lattice QCD spectrum to the scattering amplitudes and perform a calculation of elastic $DK$ scattering amplitudes which is relevant for the exotic $D_{s0}(2317)$. By analytically continuing the scattering amplitudes into the complex plane, I find a bound state pole near threshold which is in good agreement with what is found experimentally.