Dissertations / Theses: 'Unified theories of flavour'

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Lindestam, Malte. "Flavour Symmetries in SU(5) Grand Unified Theories." Thesis, KTH, Fysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297790.

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The current description of physics on the very smallest scales is given by the standard model (SM) of particle physics. It makes many good predictions and is a highly successful theory. There are however phenomena it cannot explain, and it is therefore not a complete theory of particle physics. Current efforts within theoretical particle physics are focused on theories beyond the SM which may amend its shortcomings. The SM also has aesthetic problems, in that several of its features can be seen as unnatural. There are unexplained patterns in measured masses and mixing parameters, and the fact that the SM is based on three different symmetries is rather inelegant. This too prompts theories beyond the SM. The introduction of flavour symmetries could help explain the observed patterns, whereas grand unified theories (GUTs) unify the symmetries of the SM. GUTs manage this through some large gauge group which is spontaneously broken to the SM one below some large energy scale. One such proposed group is SU(5), which is studied in this thesis. The specific model chosen is renormalizable and non-sypersymmetric and includes a 45 and a 15 representation of scalars to predict correct fermion masses. Previous studies have examined what possible flavour symmetries may be imposed on GUTs based on the group SO(10). This thesis carries out similar studies for the chosen SU(5) model. Such symmetries reduce the number of free parameters in the model and could increase the predicted proton lifetime, potentially causing better agreement with experiment. The couplings between fermions and scalars in the model are considered, and how they limit the possibilities for flavour symmetry. Several requirements are imposed on the coupling matrices of the model in the interest of agreeing with experimental data. Given these requirements, 25 distinct realistic cases with flavour symmetry are found. The symmetries of these cases are Z2, Z3, Z4 and U(1). Finally, numerical fits of the cases show that two of them are capable of fitting experimentally determined masses and mixing parameters. The two cases have Z2 and U(1) symmetry, where the second is a subcase of the first.
Den nuvarande bästa beskrivningen av partikelfysik ges av standardmodellen. Den har förutsett många fenomen och är en mycket framgångsrik teori. Det finns dock fenomen den inte kan förklara och därför är den inte en fullständig teori. Idag är teoretisk partikelfysik i huvudsak inriktad mot att försöka hitta teorier bortom standardmodellen som kan åtgärda dess problem. Standardmodellen har även vissa estetiska problem, då flera aspekter av den kan anses vara onaturliga. Det finns oförklarade mönster i uppmätta värden på massor och blandningsparametrar och det faktum att standardmodellen är baserad på tre olika symmetrier är inte så elegant. Detta har också drivit utökningar av standardmodellen. Att introducera smaksymmetrier skulle kunna förklara dessa mönster, medan så kallade storförenade teorier förenar standardmodellens symmetrier. Storförenade teorier är konstruerade kring en symmetrigrupp som spontant bryts ned till standardmodellens symmetri vid energier mindre än någon stor energiskala. En föreslagen sådan grupp är SU(5), som detta arbete studerar. Den valda modellen är renormerbar och icke-supersymmetrisk och inkluderar en 45- och en 15-representation med skalärer för att generera rätt fermionmassor. Tidigare arbeten har undersökt vilka smaksymmetrier som kan tillämpas på storförenade teorier baserade på gruppen SO(10). Detta arbete använder liknande metoder för den valda SU(5)-modellen. Smaksymmetrier minskar antalet fria parametrar i modellen och kan förlänga protonens livstid, vilket kan hjälpa teorin passa experimentella data bättre. Kopplingarna mellan fermioner och skalärer och hur dessa begränsar möjligheterna för smaksymmetri undersöks. Ett antal krav ställs på kopplingsmatriserna i modellen för att modellen ska överensstämma med experimentella data. Givet dessa krav så hittas 25 unika realistiska fall, med Z2-, Z3-, Z4- och U(1)-symmetri. Genom numeriska anpassningar av dessa fall visas att två av dem passar experimentellt uppmätta massor och blandningsparametrar. De två fallen har Z2- och U(1)-symmetri, där det andra fallet är ett specialfall av det första.

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Meroni, Aurora. "The Nature of Massive Neutrinos and Unified Theories of Flavour." Doctoral thesis, SISSA, 2013. http://hdl.handle.net/20.500.11767/4812.

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The present Ph.D. thesis is devoted to two fundamental unsolved problems of neutrino physics, which are intimately connected: determining the nature - Dirac or Majorana - of massive neutrinos, which is related with the possibility of existence of New Physics beyond that predicted by the Standard Model (SM) of particle interactions, and, discovering the origin of the patterns of neutrino masses and of leptonic mixing, stemming from new underlying symmetries in the neutrino, charged lepton and quark sectors. The remarkable experimental efforts of the last 15 years or so have delivered an enormous amount of data that have to be explained in terms of possibly economic and simple theoretical models. Moreover, exciting times are ahead of us. Currently running and future upcoming experiments under construction aim at i) high precision measurement of the parameters characterizing the neutrino oscillations, ii) identifying the neutrino mass hierarchy, and iii) establishing the status of the CP symmetry in the leptonic sector by searching for CP violation effects in neutrino oscillations. In addition, significant experimental efforts are been made to unveil the possible Majorana nature of massive neutrinos by searching for neutrinoless double beta ($\betabeta$-) decay with increasing sensitivity. Unique data on the absolute scale of neutrino masses, which is unknown at present, is expected to be provided by $\beta$-decay experiments under preparation. The first part of the Ph.D. thesis is devoted to the problem of extracting information about the New Physics if it will be experimentally established via the observation of the $\betabeta$-decay that the massive neutrinos are Majorana particles. In this case new couplings, changing the total lepton charge $L=L_e + L_\mu + L_\tau$ by two units, must be admitted in the Lagrangian of particle interactions and there is the possibility that more than one such coupling is operative in $\betabeta$-decay. We discuss four such couplings (arising in seesaw and ight-Left (L-R) symmetric models and in supersymmetric extensions of the SM with $R$-parity nonconservation) and analyze in detail the possibility to determine which couplings, if any, might be involved in $\betabeta$-decay from data on the $\betabeta$-decay half-lives of several different isotopes. In the second part of the Ph.D thesis we analyze the neutrino flavour problem in connection with new underlying symmetries in the leptonic sector. The existence of an organizing principle which could explain the pattern of masses and mixing of the neutrinos is explored in two different approaches based on the use of finite discrete non-Abelian groups. A unified model of flavour based on the symmetry group $SU(5)\times T^\prime$, incorporating the seesaw mechanism of neutrino mass generation is constructed and the predictions of this model for the neutrino mixing angles, the Dirac and Majorana CP violation phases in the neutrino mixing matrix, the sum of neutrino masses and for the $\betabeta$-decay effective Majorana mass are derived. The model can be tested in the future planned neutrino physics experiments.

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Lola, Smaragda. "Cosmological aspects of Unified Theories." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333322.

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Lee, Chin-Aik. "Selected topics in unified field theories." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 165 p, 2008. http://proquest.umi.com/pqdweb?did=1459917781&sid=10&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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McDonald, J. "Aspects of supersymmetric grand unified theories." Thesis, University of Sussex, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372726.

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Lonsdale, S. R. "Some cosmological aspects of unified theories." Thesis, University of Newcastle Upon Tyne, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378849.

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Torrejón, Maguiña Miguel Ángel. "Symmetry breaking in grand unified theories." Master's thesis, Pontificia Universidad Católica del Perú, 2014. http://tesis.pucp.edu.pe/repositorio/handle/123456789/6714.

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In this work we review the symmetry breaking mechanism of gauge theories. On the first chapters of this thesis, we review the concept of symmetry as the action of a group that leaves an object invariant, in particular Lagrangians and actions, and then develop the corresponding globally and gauge symmetric theories and the relationship between them. It also reviewed the concept and general framework of the spontaneous breaking of a symmetry for renormalizable potentials. Correspondingly, two main results for global symmetries, Noether’s theorem and Goldstone’s Theorem, are reviewed in a general setting. Chapter 3 is the most important part of this work. The Brout-Englert-Higgs mechanism is explained and used to retrieve the symmetry breaking patterns for the vector and all the second rank tensor irreducible representations of the O(n) and SU(n) groups. In general we will retrieve the vacuum expectation value (vev) for the particular representation and value of the parameters of the potential. Then, for this vev, we calculate the number of massive vector bosons of the theory. Following BEH mechanism and Goldstone’s theorem, this number is equal to the number of broken generators delining thus the particular symmetry breaking pattern. Chapter 4 is a review of the Standard Model with an aim towards Grand Unified Theories (GUTs). Lastly in Chapter 5 we review the group theory of the minimal model SU(5) in a very exhaustive way and use the results of Chapter 3 to see the breaking patterns for this particular GUT.
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DermÃsÌ†ek, Radovan. "SO(10) supersymmetric grand unified theories /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486461246816545.

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Ziegler, Robert. "Supersymmetry Breaking in Grand Unified Theories." Doctoral thesis, SISSA, 2010. http://hdl.handle.net/20.500.11767/4496.

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Supersymmetric grand unified theories (SUSY GUTs) are very interesting extensions of the minimal supersymmetric standard model (MSSM). They unify strong and electroweak interactions explaining the MSSM quantum numbers, account for presicion gauge coupling unification and stabilize the weak scale. Most importantly, they make remarkable predictions that allow to test them experimentally......

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Pernow, Marcus. "Phenomenology of SO(10) Grand Unified Theories." Licentiate thesis, KTH, Partikel- och astropartikelfysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-259605.

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Although the Standard Model (SM) of particle physics describes observations well, there are several shortcomings of it. The most crucial of these are that the SM cannot explain the origin of neutrino masses and the existence of dark matter. Furthermore, there are several aspects of it that are seemingly ad hoc, such as the choice of gauge group and the cancellation of gauge anomalies. These shortcomings point to a theory beyond the SM. Although there are many proposed models for physics beyond the SM, in this thesis, we focus on grand unified theories based on the SO(10) gauge group. It predicts that the three gauge groups in the SM unify at a higher energy into one, which contains the SM as a subgroup. We focus on the Yukawa sector of these models and investigate the extent to which the observables such as fermion masses and mixing parameters can be accommodated into different models based on the SO(10) gauge group. Neutrino masses and leptonic mixing parameters are particularly interesting, since SO(10) models naturally embed the seesaw mechanism. The difference in energy scale between the electroweak scale and the scale of unification spans around 14 orders of magnitude. Therefore, one must relate the parameters of the SO(10) model to those of the SM through renormalization group equations. We investigate this for several different models by performing fits of SO(10) models to fermion masses and mixing parameters, taking into account thresholds at which heavy right-handed neutrinos are integrated out of the theory. Although the results are in general dependent on the particular model under consideration, there are some general results that appear to hold true. The observ- ables of the Yukawa sector can in general be accommodated into SO(10) models only if the neutrino masses are normally ordered and that inverted ordering is strongly disfavored. We find that the observable that provides the most tension in the fits is the leptonic mixing angle θ2l3, whose value is consistently favored to be lower in the fits than the actual value. Furthermore, we find that numerical fits to the data favor type-I seesaw over type-II seesaw for the generation of neutrino masses.

Examinator: Professor Mark Pearce, Fysik, KTH

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Hartmann, Florian [Verfasser]. "Flavour symmetries in Pati-Salam Grand Unifying Theories / Florian Hartmann." Siegen : Universitätsbibliothek der Universität Siegen, 2015. http://d-nb.info/1074758803/34.

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Oliveira, Jorge Miguel Da Silva Borges. "Lepton flavour violation, Yukawa unification and neutrino masses in supersymmetric unified models." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340363.

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Sönnerlind, Erik. "Threshold Effects in SO(10) Grand Unified Theories." Thesis, KTH, Fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277788.

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Di, Luzio Luca. "Aspects of symmetry breaking in grand unified theories." Doctoral thesis, SISSA, 2011. http://hdl.handle.net/20.500.11767/4689.

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Ferretti, Luca. "Flavour Models, R-symmetries and non-Abelian Vortices in Supersymmetric Theories." Doctoral thesis, SISSA, 2008. http://hdl.handle.net/20.500.11767/4234.

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Bhatti, Abdul Aziz. "Fermion masses and Higgs Physics in Grand Unified Theories." Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-114132.

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Lanzagorta, Marco. "Infra-red fixed points in supersymmetric Grand Unified theories." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318836.

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Holthausen, Martin [Verfasser], and Manfred [Akademischer Betreuer] Lindner. "Towards Testable Theories with Discrete Flavour Symmetries / Martin Holthausen ; Betreuer: Manfred Lindner." Heidelberg : Universitätsbibliothek Heidelberg, 2013. http://d-nb.info/1177148064/34.

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Davis, S. C. "Microphysics of cosmic strings in supersymmetric and grand unified theories." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598393.

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In this thesis we investigate the microphysics of cosmic strings in non-minimal quantum field theories. In particular we consider theories in which fermion fields couple to the strings, and those with larger symmetry groups, such as grand unified and supersymmetric theories. By considering these extensions to the minimal model, we obtain a more realistic picture of the properties of cosmic strings. In considering grand unified theories, which have multiple phase transitions, we show that a cosmic string formed at one phase transition can cause the creation of another string-line solution at a later transition. This string-like solution will have many of the properties and implications of a normal cosmic string. We consider this effect for a general string solution, and illustrate it with a realistic SO(10) unified theory. As well as the usual abelian strings, this theory also contains more exotic string solutions. We consider both types of cosmic string. Separately, we examine the form of cosmic string solutions in supersymmetric theories, and the effect of soft supersymmetry breaking on them. We investigate the existence of conserved fermion currents in a variety of cosmic string models. We show that supersymmetry may be used to find the form of some solutions analytically. We also derive an expression for the number and type of massless fermion currents in a general model. The existence of conserved current can conflict with observations, so these results may be used to constrain models. We find the number of massless currents in the SO(10) and supersymmetric theories mentioned above. We show that currents present on a string can be destabilised by later phase transitions or supersymmetry breaking. This may allow any conflict that the current's existence has with observations to be avoided. We also examine massive fermion currents in a simple model, and determine the spectrum of such states.

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Martens, Waldemar [Verfasser], and M. [Akademischer Betreuer] Steinhauser. "Threshold Corrections in Grand Unified Theories / Waldemar Martens. Betreuer: M. Steinhauser." Karlsruhe : KIT-Bibliothek, 2011. http://d-nb.info/1014279631/34.

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Lehmkuhl, Dennis. "Spacetime matters on super-substantivalism, general relativity, and unified field theories." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527350.

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Blazek, Tomás. "Supersymmetric grand unified theories and global fits to low energy data /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487940665437557.

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Malinsky, Michal. "Quark and Lepton Masses and Mixing in Supersymmetric Grand Unified Theories." Doctoral thesis, SISSA, 2005. http://hdl.handle.net/20.500.11767/4198.

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The material is organized as follows: the first chapter is devoted to several remarks on the two basic supersymmetric GUTs - first the minimal SUSY SU(5) is considered and the main shortcomings are pointed-out in brief, and in the second part these issues are addressed concerning a general class of SO(lO) models. This provides a natural motivation to approach and describe shortly the minimal SUSY SO(lO) scheme in the second chapter. The third chapter is dedicated to a detailed study of the correlations among the quark and lepton masses and mixing within the framework with dominant triplet seesaw contribution. An extended framework, a setup with an additional, quasidecoupled Higgs multiplet transforming as 120 of 50(10), is introduced and studied in detail in chapter 4. Chapter 5 is devoted to a class of alternative seesaw schemes emerging in theories with a spinorial 16 in the Higgs sector of SUSY and split-SUSY SO(lO) GUTs. Finally, a set of Appendices is added to coment on technical points in the main text.

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Dundee, G. Benjamin (George Benjamin) Cleaver Gerald B. "Grand unified theories in higher dimensions : from the heterotic string to Randall-Sundrum /." Waco, Tex. : Baylor University, 2006. http://hdl.handle.net/2104/4905.

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Muntean, Ioan Lucian. "Unification and explanation in early Kaluza-Klein theories." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3369373.

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Thesis (Ph. D.)--University of California, San Diego, 2009.
Title from first page of PDF file (viewed September 17, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 444-468).

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Nolland, David John. "Quantum field theories with fermions in the Schrödinger representation." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4410/.

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This thesis is concerned with the Schrödinger representation of quantum field theory. We describe techniques for solving the Schrödinger equation which supplement the standard techniques of field theory. Our aim is to develop these to the point where they can readily be used to address problems of current interest. To this end, we study realistic models such as gauge theories coupled to dynamical fermions. For maximal generality we consider particles of all physical spins, in various dimensions, and eventually, curved spacetimes. We begin by considering Gaussian fields, and proceed to a detailed study of the Schwinger model, which is, amongst other things, a useful model for (3+1) dimensional gauge theory. One of the most important developments of recent years is a conjecture by Mal-dacena which relates supergravity and string/M-theory on anti-de-Sitter spacetimes to conformal field theories on their boundaries. This correspondence has a natural interpretation in the Schrödinger representation, so we solve the Schrödinger equation for fields of arbitrary spin in anti-de-Sitter spacetimes, and use this to investigate the conjectured correspondence. Our main result is to calculate the Weyl anomalies arising from supergravity fields, which, summed over the supermultiplets of type JIB supergravity compactified on AdS(_s) x S(^5) correctly matches the anomaly calculated in the conjecturally dual N = 4 SU{N) super-Yang-Mills theory. This is one of the few existing pieces of evidence for Maldacena's conjecture beyond leading order in TV.

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Kapner, Daniel J. "A short-range test of Newton's gravitational inverse-square law /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/9694.

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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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Jansson, Henrik. "Unification in Particle Physics." Thesis, Uppsala universitet, Högenergifysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-295813.

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During the twentieth century, particle physics developed into a cornerstone of modern physics, culminating in the Standard Model. Even though this theory has proved to be of extraordinary power, it is still incomplete in several respects. It is our aim in this bachelor thesis to discuss some possible theories beyond the Standard Model, the main focus being on Grand Unified Theories, while also taking a look at attempts of further unication via discrete family symmetry. At the heart of all these theories lies the concept of local gauge invariance, which is introduced as a fundamental principle, followed by an overview of the Standard Model itself. No theory has so far managed to unify all elementary particles and their interactions, but some interesting features are highlighted. We also give a hint at some possible paths to go in the future in the quest for a unication in particle physics.
Under 1900-talet utvecklades partikelfysiken till en av de fundamentala teorierna inom fysiken, och kom att sammanfattas i den s.k. Standardmodellen. Även om denna modell rönt exceptionella framgånger vad gäller beskrivningen av elementarpartiklar och deras växelverkan, är den fortfarande ofullständig på flera sätt. Syftet med denna kandidatuppsats är att diskutera möjliga teorier bortom Standardmodellen såsom Storförenande Teorier och diskreta familjesymmetrier vars avsikt är att koppla samman de tre familjerna av fermioner i Standardmodellen. Men först introduceras idén om lokal gaugeinvarians, vilken ligger till grund for dessa teorier, varpå en översikt av Standardmodellen följer. Ingen teori har ännu lyckats ge en helt tillfredsställande bild av elementarpartiklar och deras interaktion, men en del intressanta egenskaper hos föreslagna teorier belyses i denna uppsats. Slutligen ges en del spekulativa förslag på väger att gå i framtida försök till föreningar inom partikelfysiken.

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Riad, Stella. "Studies of effective theories beyond the Standard Model." Licentiate thesis, KTH, Teoretisk partikelfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-154048.

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The vast majority of all experimental results in particle physics can be described by the Standard Model (SM) of particle physics. However, neither the existence of neutrino masses nor the mixing in the leptonic sector, which have been observed, can be described within this model. In fact, the model only describes a fraction of the known energy in the Universe. Thus, we know there must exist a theory beyond the SM. There is a plethora of possible candidates for such a model, such as supersymmetry, extra dimensional theories, and string theory. So far, there are no evidence in favor of these models. These theories often reside at high energies, and will therefore be manifest as effective theories at the low energies experienced here on Earth. A first example in extra-dimensional theories. From our four-dimensional point of view, particles which propagate through the extra dimensions will effectivel be perceived as towers of heavy particles. In this thesis we consider an extra-dimensional model with universal extra dimensions, where all SM particles are allowed to propagate through the extra dimensions. Especially, we place a bound on the range of validity for this model. We study the renormalization group running of the leptonic parameters as well as the Higgs self-coupling in this model with the neutrino masses generated by a Weinberg operator. Grand unified theories, where the gauge couplings of the SM are unified into a single oe at some high energy scale, are motivated by the electroweak unification. The unification must necessarily take place at energies many orders of magnitude greater than those that ever can be achieved on Earth. In order to make sense of the theoru, ehich is given at the grand unified scale, at the electroweak scale, the symmetry at the grand unified scale is broken down to the SM symmetry. Within these models the SM is considered as an effective field theory. We study renormalization group running of the leptonic parameters in a non-supersymmetric SO(10) model which is broken in two steps via the Pati-Salam group. Finally, the discovery of the new boson at the LHC provides a new opportunity to search for physics beyond the SM. We consider an effective model where the magnitudes of the couplings in the Higgs sector are scaled by so-called coupling scale factors. We perform Bayesian parameter inference based on the LHC data. Furthermore, we perform Bayesian model comparison, comparing models where one or several of the Higgs couplings are allowed, to the SM, where the couplings are fixed.

QC 20141020

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Santapuri, Sushma. "Unified Continuum Modeling of Fully Coupled Thermo-Electro-Magneto-Mechanical Behavior, with Applications to Multifunctional Materials and Structures." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354726155.

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Senoguz, Vedat Nefer. "Aspects of inflationary models and unification." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 114 p, 2007. http://proquest.umi.com/pqdweb?did=1251906411&sid=1&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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Schreiber, Gunhild Ursula. "Introduction to supersymmetry." Master's thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/14358.

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Includes bibliographical references.
The tendency in theoretical physics, particularly in the past few decades, has been towards unification: over the years it has emerged that increasingly many physical phenomena can be explained by a common underlying theory. Symmetry principles, both global and local, play an important role in this unification programme. Global symmetries often account for approximate regularities we observe in nature - local or gauge symmetries are understood as basic symmetries which lie at the heart of the interactions of the constituents of matter.

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Riad, Stella. "Phenomenology of neutrino properties, unification, and Higgs couplings beyond the Standard Model." Doctoral thesis, KTH, Teoretisk partikelfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-202311.

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The vast majority of experiments in particle physics can be described by the Standard Model of particle physics (SM). However, there are indications for physics beyond it. The only experimentally demonstrated problem of the model is the difficulty to describe neutrino masses and leptonic mixing. There is a plethora of models that try to describe these phenomena and this thesis investigates several possibilities for new models, both full theories and effective frameworks. The values of the parameters in a model are dependent on the energy scale and we say that the parameters run. The exact behavior of the running depends on the model and it provides a signature of the model. For a model defined at high energies it is necessary to run the parameters down to the electroweak scale in order to perform a comparison to the known values of observed quantities. In this thesis, we discuss renormalization group running in the context of extra dimensions and we provide an upper limit on the cutoff scale. We perform renormalization group running in two versions of a non-supersymmetric SO(10) model and we show that the SM parameters can be accommodated in both versions. In addition, we perform the running for the gauge couplings in a large set of radiative neutrino mass models and conclude that unification is possible in some of them. The Higgs boson provides new possibilities to study physics beyond the SM. Its properties have to be tested with extremely high precision before it could be established whether the particle is truly the SM Higgs boson or not. In this thesis, we perform Bayesian parameter inference and model comparison. For models where the magnitude of the Higgs couplings is varied, we show that the SM is favored in comparison to all other models. Furthermore, we discuss lepton flavor violating processes in the context of the Zee model. We find that these can be sizeable and close to the experimental limits.

QC 20170221

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Laksaniyanon, Benchamat. "Acceptance Theories for Behavior in Conducting Research: Instructors in the Rajabhat University System, Thailand." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc848155/.

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Responding to globalization and its effects on education and research development, the Thai government decided to push all public universities to become autonomous and establish a system of quality assurances. The establishment of quality assurances has had a large impact on many Thai instructors, especially in new public universities. Thai instructors are now forced to more focus on conducting research because the number of research publications is regarded as one of the main criteria for quality universities. The purpose of this study is to investigate the key factors, at the individual and university levels, which impact on the instructors' behavior in conducting research of the full-time instructors in the faculty of Management Science from the Rajabhat Universities in Thailand. The current study will help explain how and why the instructors accept or refuse to conduct research and provide insight into the salient factors motivating the instructors to produce more research by conducting HLM. Data were collected from 694 participants at 37 institutions via a questionnaire survey. The findings revealed that there was no difference among these 37 universities on behavior in conducting research. The key factors statistically influencing behavior in conducting research of the instructors were facilitating conditions, academic degree, social influence, and usefulness as well as ease of conducting research that the instructors perceived. This study gained 46% of effect size.

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Crisafulli, Daniela. "Advanced modelling of multilayered composites and functionally graded structures by means of Unified Formulation." Thesis, Paris 10, 2013. http://www.theses.fr/2013PA100055/document.

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La plupart des problèmes d'ingénierie des deux derniers siècles ont été résolus grâce à des modèles structuraux pour poutres, plaques et coques. Les théories classiques, tels que Euler-Bernoulli, Navier et de Saint-Venant pour les poutres, et Kirchhoff-Love et Mindlin-Reissner pour plaques et coques, ont permis de réduire le problème générique 3-D, dans le problème unidimensionnel pour les poutres et deux dimensionnelle pour les coques et les plaques. Théories raffinés d'ordre supérieur ont été proposées au cours du temps, comme les modèles classiques ne consentez pas à d'obtenir une complète domaine des contraintes et des déformations. La Carrera Unified Formulation (UF) a été proposé au cours de la dernière décennie, et permet de développer un grand nombre de théories structurelles avec un nombre variable d'inconnues principales au moyen d'une notation compacte et se référant à des nuclei fondamentales. Cette formulation unifiée permet de dériver carrément des modèles structurels d'ordre supérieur, pour les poutres, plaques et coques. Dans ce cadre, cette thèse vise à étendre la formulation pour l'analyse des structures fonctionnellement gradués (FGM), en introduisant aussi le problème thermo-mécanique, dans le cas des poutres fonctionnellement gradués. Suite à la formulation unifiée, les variables génériques déplacements sont écrits en termes de fonctions de base, qui multiplie les inconnues. Dans la deuxième partie de la thèse, de nouvelles fonctions de bases pour la modélisation des coques, qui représentent une approximation trigonométrique des variables déplacements, sont pris en compte
Most of the engineering problems of the last two centuries have been solved thanks to structural models for both beams, and for plates and shells. Classical theories, such as Euler-Bernoulli, Navier and De Saint-Venant for beams, and Kirchhoff-Love and Mindlin- Reissner for plates and shells, permitted to reduce the generic 3-D problem, in onedimensional one for beams and two-dimensional for shells and plates. Refined higher order theories have been proposed in the course of time, as the classical models do not consent to obtain a complete stress/strain field. Carrera Unified Formulation (UF) has been proposed during the last decade, and allows to develop a large number of structural theories with a variable number of main unknowns by means of a compact notation and referring to few fundamental nuclei. This Unified Formulation allows to derive straightforwardly higher-order structural models, for beams, plates and shells. In this framework, this thesis aims to extend the formulation for the analysis of Functionally Graded structures, introducing also the thermo-mechanical problem, in the case of functionally graded beams. Following the Unified Formulation, the generic displacements variables are written in terms of a base functions, which multiplies the unknowns. In the second part of the thesis, new bases functions for shells modelling, accounting for trigonometric approximation of the displacements variables, are considered

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Schradin, Leslie J. "Textures, model building, and orbifold gauge anomalies research in three topics in physics beyond the standard model /." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1166571116.

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Elgammal, Sherif. "Detection of high energy electrons in the CMS detector at the LHC." Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210208.

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Détection et identification de la réaction quark + anti-quark -> e+ + e- à l'aide du détecteur CMS (Compact Muon Solenoid) auprès du Grand Collisionneur de Hadrons du CERN, le LHC. Cette réaction permet de tester avec précision le Modèle Standard et de rechercher d'éventuelles nouvelles particules (Z') prédites par les théories de grande unification (GUT) et par les modèles à dimensions spatiales supplémentaires.
Doctorat en Sciences
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Coy, Rupert Lawrence. "Two approaches to new physics : effective analyses of lepton observables & composite models of axions." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS052.

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Avec des preuves expérimentales convaincantes que le modèle standard (SM) est incomplet, il est nécessaire d’examiner la manière dont il devrait être étendu.Dans cette thèse, nous étudions des scénarios motivés de physique nouvelle au-dela de l’échelle électrofaible et examinons leurs conséquences aux basses énergies. Deux approches sont retenues, l’une inspirée notamment par le vaste programme expérimental des observables du lepton, l’autre inspirée par les avantages théoriques d’une nouvelle physique fortement couplée proche de l'ordre de l’échelle du TeV.La partie I met l’accent sur les déviations du SM dans le secteur des leptons, analysées dans le cadre des théories effectives des champs (EFT). Nous calculons les EFT à une boucle pour les modèles de `seesaw' de types I et III, à partir desquels nous examinons les observables leptoniques de précision et leurs corrélations. Notamment, nous constatons que dans de nombreux cas, les coefficients de Wilson conservant la saveur fixent une limite supérieure à ceux qui violent la saveur. Nous réalisons également une étude complète des explications générées par boucle des indications récentes de non-universalité des saveurs dans les désintégrations du méson B et classifions les modèles simplifiés viables.La deuxième partie traite de la nouvelle physique composite en tant que solution au problème de CP forte. Des théories de jauge de confinement supplémentaires sont une extension intéressante du SM, apparaissant par exemple dans les modèles de Higgs composites, car leur dynamique stabilise la nouvelle échelle. De plus, un axion peut émerger sous la forme d'un boson composite pseudo-Nambu-Goldstone.Nous démontrons qu'une séquence de secteurs fortement couplés peut donner lieu à un mécanisme Clockwork, qui sépare efficacement les échelles dynamiques et d'interaction d'une théorie. Nous construisons avec succès des modèles d'un axion QCD invisible à partir de la dynamique à l'échelle TeV, dans lesquels la symétrie de Peccei-Quinn de U(1) apparaît accidentellement. Les modèles contiennent plusieurs candidats de matière noire
With compelling experimental evidence that the Standard Model (SM) is incomplete, it is necessary to consider how it should be extended. In this thesis, we study motivated scenarios of new physics above the electroweak scale and examine their low-energy consequences. Two approaches are taken, one driven in particular by the vast experimental programme probing lepton observables, the other inspired by the theoretical advantages of new, strongly-coupled physics close to the TeV-scale.The focus of Part I is on departures from the SM in the lepton sector, analysed through the framework of Effective Field Theories (EFTs). We derive the EFTs at one-loop for the type-I and type-III seesaw models, from which we examine precision lepton observables and their correlations. Notably, we find that in many cases the flavour-conserving Wilson coefficients set an upper bound on the flavour-violating ones. We also perform a comprehensive study of loop-generated explanations of the recent hints of flavour non-universality in B-meson decays and classify viable simplified models.Part II addresses composite new physics as a solution to the strong CP problem. Additional confining gauge theories are an attractive extension of the SM, appearing for instance in composite Higgs models, because their dynamics stabilise the new scale. Moreover, an axion may emerge as a composite pseudo-Nambu-Goldstone boson. We demonstrate that a sequence of strongly-coupled sectors can give rise to a clockwork mechanism, which efficiently separates the dynamical and interaction scales of a theory. We successfully construct models of an invisible QCD axion from TeV-scale dynamics, wherein the U(1) Peccei-Quinn symmetry arises accidentally. The models contain multiple dark matter candidates

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Antão, Laura H. "Effects of ecological scaling on biodiversity patterns." Thesis, University of St Andrews, 2018. http://hdl.handle.net/10023/13606.

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Biodiversity is determined by a myriad of complex processes acting at different scales. Given the current rates of biodiversity loss and change, it is of paramount importance that we improve our understanding of the underlying structure of ecological communities. In this thesis, I focused on Species Abundance Distributions (SAD), as a synthetic measure of biodiversity and community structure, and on Beta (β) diversity patterns, as a description of the spatial variation of species composition. I systematically assessed the effect of scale on both these patterns, analysing a broad range of community data, including different taxa and habitats, from the terrestrial, marine and freshwater realms. Knowledge of the scaling properties of abundance and compositional patterns must be fully integrated in biodiversity research if we are to understand biodiversity and the processes underpinning it, from local to global scales. SADs depict the relative abundance of the species present in a community. Although typically described by unimodal logseries or lognormal distributions, empirical SADs can also exhibit multiple modes. However, the existence of multiple modes in SADs has largely been overlooked, assumed to be due to sampling errors or a rare pattern. Thus, we do not know how prevalent multimodality is, nor do we have an understanding of the factors leading to this pattern. Here, I provided the first global empirical assessment of the prevalence of multimodality across a wide range of taxa, habitats and spatial extents. I employed an improved method combining two model selection tools, and (conservatively) estimated that ~15% of the communities were multimodal with strong support. Furthermore, I showed that the pattern is more common for communities at broader spatial scales and with greater taxonomic diversity (i.e. more phylogenetically diverse communities, since taxonomic diversity was measured as number of families). This suggests a link between multimodality and ecological heterogeneity, broadly defined to incorporate the spatial, environmental, taxonomic and functional variability of ecological systems. Empirical understanding of how spatial scale affects SAD shape is still lacking. Here, I established a gradient in spatial scale spanning several orders of magnitude by decomposing the total extent of several datasets into smaller subsets. I performed an exploratory analysis of how SAD shape is affected by area sampled, species richness, total abundance and taxonomic diversity. Clear shifts in SAD shape can provide information about relevant ecological and spatial mechanisms affecting community structure. There was a clear effect of area, species richness and taxonomic diversity in determining SAD shape, while total abundance did not exhibit any directional effect. The results supported the findings of the previous analysis, with a higher prevalence of multimodal SADs for larger areas and for more taxonomically diverse communities, while also suggesting that species spatial aggregation patterns can be linked to SAD shape. On the other hand, there was a systematic departure from the predictions of two important macroecological theories for SAD across scales, specifically regarding logseries distributions being selected only for smaller scales and when species richness and number of families were proportionally much smaller than the total extent. β diversity quantifies the variation in species composition between sites. Although a fundamental component of biodiversity, its spatial scaling properties are still poorly understood. Here, I tested if two conceptual types of β diversity showed systematic variation with scale, while also explicitly accounting for the two β diversity components, turnover and nestedness (species replacement vs species richness differences). I provided the first empirical analysis of β diversity scaling patterns for different taxa, revealing remarkably consistent scaling curves. Total β diversity and turnover exhibit a power law decay with log area, while nestedness is largely insensitive to scale changes. For the distance decay of similarity analysis, while area sampled affected the overall dissimilarity values, rates of similarity were consistent across large variations in sampled area. Finally, in both these analyses, turnover was the main contributor to compositional change. These results suggest that species are spatially aggregated across spatial scales (from local to regional scales), while also illustrating that substantial change in community structure might occur, despite species richness remaining relatively stable. This systematic and comprehensive analysis of SAD and community similarity patterns highlighted spatial scale, ecological heterogeneity and species spatial aggregation patterns as critical components underlying the results found. This work expanded the range of scales at which both theories deriving SAD and community similarity studies have been developed and tested (from local plots to continents). The results here showed strong departures from two important macroecological theories for SAD at different scales. In addition, the overall findings in this thesis clearly indicate that unified theories of biodiversity (or assuming a set of synthetic minimal assumptions) are unable to accommodate the variability in SADs shape across spatial scales reported here, and cannot fully reproduce community similarity patterns across scales. Incorporating more realistic assumptions, or imposing scale dependent assumptions, may prove to be a fruitful avenue for ecological research regarding the scaling properties of SAD and community similarity patterns. This will allow deriving new predictions and improving the ability of theoretical models to incorporate the variability in abundance and similarity patterns across scales.

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Junior, Mauricio Francisco Caliri. "Contribuição para teoria de placas: análises estruturais de compósitos laminados e estruturas sanduíches via formulações unificadas." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/18/18148/tde-26072016-101122/.

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Em engenharia, a quantidade de problemas geométricos complexos que precisam ser resolvidos empregando teorias de placas ou cascas é notável. Esta é a razão por que há tantas teorias que buscam simplificar os problemas tridimensionais em outros menos custosos computacionalmente. Além disso, o aumento atual do uso de estruturas sanduíche requer que as formulações bidimensionais sejam mais precisas. Esta tese, num primeiro momento, compila a maioria das teorias de placa, comentando as principais diferenças, vantagens e desvantagens de cada uma. As formulações bidimensionais de placas laminadas são classificadas principalmente de acordo com o tratamento da coordenada na direção normal a superfície da mesma: Camada Única Equivalente (ESL), ESL refinada (teorias Zig-Zag) e Teorias Discretas ou de Camada (LW). Cada uma destas teorias é revista juntamente com as hipóteses de placas que são feitas para cada uma das camadas ou para o laminado como um todo. Para resolver tais problemas estruturais em engenharia, métodos numéricos são normalmente utilizados. Portanto, num segundo momento, alguns métodos de solução são citados e revisados, mas o foco é dado ao Método dos Elementos Finitos (MEF). A contribuição deste trabalho consiste na implementação de um novo método de solução de compósitos laminados e estruturas sanduíche com base em um sistema unificado de Formulação Generalizada (GUF) via MEF. Um elemento quadrilátero de 4 nós foi desenvolvido e avaliado com um código de Elementos Finitos desenvolvido pelo presente autor. Os requisitos para continuidade do tipo C-1 são respeitados para a variável de deflexão da placa. Esse método é nomeado de Formulação Generalizada do Caliri (CGF). Resultados para placas isotrópicas, placas de laminado compósito e estruturas sanduíche consideradas finas ou espessas são comparados com dados da literatura e soluções via Abaqus. Os resultados obtidos ao longo da espessura reforçam a necessidade de soluções de placa não-lineares para placas espessas (laminadas ou não). Mostrou-se que as soluções estáticas e dinâmicas empregando o método proposto fornecem resultados coerentes quando comparados com outros métodos de solução. Dentre os diversos estudos de caso investigados, verificou-se que é possível se obter resultados com alta concordância. Para uma estrutura sanduíche com núcleo macio, o resultado de deslocamento previsto para um carregamento estático chega a 99.8% de concordância e o resultado de uma análise modal da mesma estrutura mostra uma concordância de 99.5% com os resultados de um modelo feito com elementos 3D em um programa comercial de elementos finitos.
In engineering, the amount of complex geometrical problems, which need to be solved by using plates and shells theories, is remarkable. This is the reason why there are so many plate and shell theories which attempt to simplify three dimensional problems into ones with low computational cost. Additionally, the current increasing use of sandwich structures requires that the two dimensional formulations be accurate enough. First, this thesis compiles most of the plate theories from the literature and quotes the main differences, advantages and weaknesses of each one. The bi-dimensional laminated plate formulations are mainly classified according to the treatment of the variable in the normal direction of the plate surface: Equivalent Single Layer (ESL), Refined ESL (Zig-Zag theories) and Layer-Wise (LW) theories. Each one of these theories is reviewed along with the plate hypotheses which are made for each ply and/or laminate. To solve such complex structural engineering problems, numerical methods are normally used. Second, few solution methods are reviewed and quoted, but focus is given to the Finite Element Method (FEM). The contribution of this work is the implementation of a new solution method for laminated composites and sandwich structures based on a Generalized Unified Formulation (GUF) via FEM. A quadrilateral 4-node element was developed and evaluated using in-house Finite Element program. The C-1 continuity requirements is fulfilled for the transversal displacement field variable. This method is tagged as Caliri\'s Generalized Formulation (CGF). Results for isotropic plates, laminated composite plates and sandwich structures for thin and thick laminates are compared with literature data and solutions via Abaqus. The through-the-thickness profile results reinforce the need for non-linear plate (laminated or not) solutions. It was shown that the static and dynamic solutions employing the proposed solution method yield coherent results when compared with other solution methods. Among the different case studies investigated, it was verified that it is possible to obtain results with high agreement. For a soft-core sandwich structure, the displacement result for a static loading is reported as high as 99.8% and the result of a modal analysis of the same structure shows an accuracy of 99.5%, comparing to the results from a 3D finite element model built with a commercial software.

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Charaf, Otman. "Study of Drell-Yan production in the di-electron decay channel and search for new physics at the LHC." Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210031.

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Cette these a pour sujet la recherche de nouvelle physique et l'etude de la production Drell-Yan dans le canal di-electron a l'aide du detecteur CMS au LHC. Certaines theories au dela du Modele Standard (extra dimensions, theories de grande unification) predisent l'existence de particules massives pouvant se desintegrer en une paire d'electrons. La selection des evenements recherches est presentee et etudiee. La strategie d'analyse est introduite et testee. Enfin, l'analyse des premieres donnees a 7 TeV est decrite et les resultats sont commentes.
Doctorat en Sciences
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Cosme, Nicolas. "Matter asymmetry and gauge unification." Doctoral thesis, Universite Libre de Bruxelles, 2004. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211132.

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Pourquoi reste-t-il de la matière dans l’univers ?Depuis la découverte de l’anti-matière, miroir de la matière dont nous sommes constitués et s’annihilant de prime abord parfaitement avec cette dernière, ce mystère stimule l’étude des propriétés communes et distinctes entre particules et anti-particules.

Dans ce cadre, il a été établi au vu des interactions dites de jauge (en particulier les interactions électrofaibles) que la symétrie intrinsèque entre particules et anti-particules est la combinaison subtile du conjugué de charge (C) et de la parité d’espace (P) :la symétrie CP. Ainsi, un comportement distinct entre matière et anti-matière est caractérisé au niveau fondamental par une violation de CP.

D’une part, une telle violation a été mise en évidence expérimentalement dans la désintégration de mesons K et B, où la production de particules dans certains canaux est favorisée. D’autre part, la violation de CP est l’une des conditions requises à la création d’un excès de matière durant l’évolution de l’univers.

Dans la présente thèse, nous étudions deux aspects de cette asymétrie entre matière et anti-matière.

Tout d’abord, un scénario de création d’un excès de matière dans l’évolution de l’univers basé sur la désintégration de neutrinos lourds est étudié. Les récents résultats expérimentaux sur l’existence d’une masse pour les neutrinos rendent très attractif ce scénario. Bien que le schéma général repose uniquement sur les interactions liées à la masse des particules (secteur scalaire), nous le prolongeons ici dans la perspective plus naturelle de l’unification des interactions de jauge, seule motivation complète à l’inclusion de neutrinos lourds dans le spectre des particules. L’inclusion d’interactions de jauge liées aux neutrinos lourds complète ainsi la description. Les résultats tirés sur les paramètres de masse des neutrinos, grandes inconnues de la physique des particules, s’en voient modifiés de manière importante.

Ensuite, la question de l’origine de la violation de CP est posée. En effet, dans la description standard des interactions faibles, la violation de CP est explicite et résulte uniquement de la liberté pour les couplages de masse (couplages de Yukawa) d’être des nombres complexes. Ainsi, aucune compréhension fondamentale sur la différence de comportement entre particules et anti-particules n’est apportée.

Nous proposons dans ce sens une source de violation de CP par la compactification d’une théorie de jauge dans un espace de dimensions étendues. A partir de couplages réels, une valeur classique de la composante supplémentaire des bosons de jauge fournit une masse effective complexe aux fermions. Les conditions de l’obtention d’une violation de CP physique sont alors étudiées. Nous identifions la structure minimale pour rendre compte des interactions électrofaibles tout en incluant une source de violation de CP dans ce contexte. L’unification avec les interactions fortes est alors établie dans une structure qui apporte une lumière différente sur les schémas d’unification usuels.

Doctorat en sciences, Spécialisation physique
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Thomas, Laurent. "Search for new heavy narrow resonances decaying into a dielectron pair with the CMS detector." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209221.

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Le sujet de la présente thèse porte sur la recherche de nouvelles particules très massives se désintégrant en une paire électron-positron avec le détecteur CMS.

Le démarrage en 2010 du Large Hadron Collider au CERN marque le début d'une nouvelle ère en physique des particules. L'énergie et l'intensité de ses faisceaux de protons, inégalées à ce jour, offre en effet la possibilité d'étudier les lois décrivant les constituants ultimes de la matière et leurs interactions à des énergies jusqu'alors inaccessibles et d'étudier des processus rares.

La découverte récente par les expériences ATLAS et CMS du boson scalaire prédit par la théorie de la brisure de symétrie électro-faible constitue ainsi la première percée du programme de recherche du LHC et confirme la théorie actuelle décrivant la physique subatomique, le Modèle Standard.

Il est cependant largement admis que cette théorie, bien que hautement prédictive et jamais mise en défaut expérimentalement jusqu'à présent, ne constitue qu'une approximation à basse énergie d'une théorie plus fondamentale.

Cette thèse décrit la recherche de nouvelles particules, prédites par plusieurs modèles au delà du Modèle Standard, via leur désintégration en une paire électron-positron de haute énergie.

La reconstruction et la sélection des électrons de haute énergie par le détecteur CMS sont des éléments centraux de cette analyse et sont étudiées en détail. Divers critères sont développés afin de distinguer les électrons des autres types d'objets physiques produits lors de collisions de protons, tels que les jets. L'intensité des faisceaux du LHC est telle que plusieurs collisions ont lieu simultanément dans le détecteur et il est montré que l'efficacité de sélection des électrons dépend fortement du nombre de ces interactions. Une technique est donc mise au point pour corriger cet effet.

Une méthode pour mesurer l'efficacité de la sélection directement sur les données est également développée. Celle-ci permet de confirmer les mesures obtenues à partir de simulations, jusqu'à des impulsions transverses de plusieurs centaines de GeV.

Le spectre de masse des paires diélectron est établi pour les données enregistrées en 2012 à une énergie dans le centre de masse des protons de 8 TeV, et un excès localisé d'événements est recherché. Aucune déviation significative par rapport au bruit de fonds attendu n'est observée et des limites très contraignantes sont établies sur le rapport de la section efficace de production d'une nouvelle résonance diélectronique et de celle mesurée au pic du boson Z. Ces résultats sont utilisés pour fixer des limites inférieures sur la masse de nouvelles particules prédites par certains modèles.

Le redémarrage du LHC en 2015 avec une énergie de 6.5 TeV par faisceau de proton élargira fortement le potentiel de découverte de ces résonances. En cas de découverte d'un signal, ses propriétés (telles que le spin ou l'asymétrie avant-arrière) seront étudiées avec attention. Des projections sur la précision qui pourrait alors être atteinte pour ces mesures sont donc finalement présentées en fonction de la luminosité intégrée collectée.
Doctorat en Sciences
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Datta, Alakabha. "Topics in heavy flavor decays and grand unified theories." Thesis, 1995. http://hdl.handle.net/10125/10086.

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Iyer, Abhishek Muralidhar. "Randall-Sundrum Model as a Theory of Flavour." Thesis, 2013. http://etd.iisc.ernet.in/2005/3381.

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The discovery of the Higgs boson by the LHC provided the last piece of the puzzle neces- sary for the Standard Model (SM) to be a successful theory of electroweak scale physics. However there exist various phenomenological reasons which serve as pointer towards the existence of physics beyond the Standard Model. For example the explanation for the smallness of the neutrino mass, baryon asymmetry of the universe, the presence of dark matter and dark energy etc. are not within purview of the Standard Model. Con- ceptual issues like the gauge hierarchy problem, weakness of gravity provide some of the theoretical motivation to pursue theories beyond the SM. We consider scenarios with warped extra-dimensions (Randall-Sundrum (RS) Model ) as our preferred candidate to answer some of the questions raised above. RS model gives an elegant geometric solution to address the hierarchy between the two fundamental scales of nature i.e. Planck scale and electroweak scale. In addition to this, the geometry of RS serves as a useful setup wherein the fermion mass hierarchy problem can also be solved. The goal of this thesis is to investigate whether RS model can be an acceptable theory of avour while at the same time serving as a solution to the hierarchy problem. In Chapter[1] we begin with a brief introduction of the SM, highlighting issues which pro- vides the necessary motivation for constructing new physics models. Various candidates of Beyond Standard Model (BSM) physics are introduced and a few preliminaries es- sential to understand frameworks with additional spatial-dimensions ( at and warped) is provided. In Chapter[2] we specialize to the case of warped extra-dimensions and motivate the need to have the SM elds in the bulk. Mathematical details related to the analysis of various spin elds (0; 12; 1 and 2) in a warped background necessary to understand relevant phenomenology is provided. The lack of knowledge of Dirac or Majorana nature of the neutrino leads to a wide variety of possibilities as far as neutrino mass generation is concerned. In Chapter[3] we focus on the leptonic sector where three cases of neutrino mass generation are consid- ered: a)Planck Scale lepton number violation (LLHH case) b) Dirac neutrinos c) Bulk Majorana mass terms. We then study the implications of each case on the charged lepton mass tting. The case with Planck scale lepton number violation in normal RS scenario requires large and negative values for the bulk mass parameters for the charged singlets cE. Dirac neutrinos and the case with Bulk Majorana mass terms give good t to data. For completeness, the ts for the hadronic sector is provided in the appendix. In Chapter[4] avour violation for each of three cases introduced in Chapter[3] is studied. For the case with Planck scale lepton number violation, the non-perturbative Yukawa coupling between the SM singlets and the KK states render the higher order diagrams incalculable. Lepton avour violation (LFV) is particularly large for the Dirac case and the bulk Majorana case for low Kaluza-Klein(KK) mass scales. We then invoke the ansatz of Minimal Flavour violation to suppress LFV with low lying KK scales and examples of avour group is provided for both cases. In Chapter[5] we present an example with a type II two Higgs doublet model applied to the LLHH case. The setup o ers a solution where LLHH scenario can be consistently realized in RS model, where the masses and mixing angles in the leptonic sector can bet with O(1) choice of bulk parameters. Assumption of global lepton number conservation (like in Dirac neutrinos) could lead to problems in theories of quantum gravity where it does not hold. This leads us to the question whether Dirac neutrinos can be naturally realized in nature. In Chapter[6] we consider the special case of bulk Majorana mass encountered in Chapter[3] where the bulk Dirac mass terms for the right handed neutrino is set to zero. We nd that this leads to a case where the e ective zero mode neutrino mass is of Dirac type with negligible e ects from the tower of Majorana states. In Chapter[7] we consider RS at the GUT scale which no longer serves as a solution to the hierarchy problem. SUSY is introduced in the bulk and the low energy SUSY serves as a solution to the hierarchy problem. Such models serve as a useful alternative to SUSY models with family symmetries (e.g. Froggatt-Nielsen Model). However the solutions to the Yukawa hierarchy problem are constrained due to anomaly cancellation conditions. In Chapter[8] supersymmetry breaking due to radion mediation in addition to brane localized sources is considered and detailed analysis of the running of soft masses and the low energy avour observables is considered for both cases separately. In Chapter[9] we conclude and present future directions.

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47

Thomson, Rowan. "Holographic studies of thermal gauge theories with flavour." Thesis, 2007. http://hdl.handle.net/10012/3229.

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The AdS/CFT correspondence and its extensions to more general gauge/gravity dualities have provided a powerful framework for the study of strongly coupled gauge theories. This thesis explores properties of a large class of thermal strongly coupled gauge theories using the gravity dual. In order to bring the holographic framework closer to Quantum Chromodynamics (QCD), we study theories with matter in the fundamental representation. In particular, we focus on the holographic dual of SU(Nc) supersymmetric Yang-Mills theory coupled to Nf<

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48

Ohmann, Paul R. "Phenomenology of supersymmetric grand unified theories." 1994. http://catalog.hathitrust.org/api/volumes/oclc/32026904.html.

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Thesis (Ph. D.)--University of Wisconsin--Madison, 1994.
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leave 152-167).

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Summy, Heaya Ann. "SO(10) supersymmetric grand unified theories from cosmology to colliders /." 2008. http://etd.lib.fsu.edu/theses/available/etd-11042008-143042.

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Thesis (Ph. D.)--Florida State University, 2008.
Advisor: Howard Baer, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed Feb. 3, 2009). Document formatted into pages; contains xiii, 108 pages. Includes bibliographical references.

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50

Bhatti, Abdul Aziz [Verfasser]. "Fermion masses and Higgs physics in grand unified theories / submitted by Abdul Aziz Bhatti." 2010. http://d-nb.info/1002224055/34.

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Dissertations / Theses on the topic 'Unified theories of flavour'

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