Made available in DSpace on 2015-05-14T12:14:18Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 939261 bytes, checksum: f8a1456cf29d5789dabc615e68c9a352 (MD5) Previous issue date: 2009-08-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The standard model does not predict mass for the neutrinos, and any evidence that neutrinos are massive particles is a signal of new physics. Recent experimental data on neutrino oscillations provide a convincing evidence that neutrinos are massive and very light particles, with mass in the scale of eVs. Thus, we must extend the standard model in order to incorporate mass terms for the neutrinos, and find a mechanism to explain the value of observed masses. It is almost a consensus that the See-Saw mechanism provides the most elegant explanation for the observed value of the masses of neutrinos. In this work we implement the See-Saw mechanism in the 3-3-1 model with right handed neutrinos. The implementation is made with the introduction of a scalar sextet and the spontaneous breaking of the lepton number. We identi fied the Majoron as a singlet by the group SU(2)LNU(1)y, which makes it safe under the current limits of the eletroweak data. The main result of this work is that the See-Saw mechanism works at the TeV scale, and as a result the mass of right handed neutrinos lies in the electroweak scale, providing a great opportunity to test their existence in the current detectors. Finally we present one of the most interesting properties of the model, the Flavour Changing Neutral Current (FCNC). We show the explicit form of this lagrangian and motivate the study of this phenomenon through Hadronic and leptonic interactions that enable their testability in the next generation of accelerators. / O modelo padrão não prediz massa para os neutrinos, e qualquer evidência que os neutrinos sejam partículas massivas é um sinal de nova física. Dados experimentais recentes sobre oscilações de neutrinos fornecem uma evidência convincente de que os neutrinos são partículas massivas e muito leves, com massa na escala dos eVs. Assim, devemos estender o modelo padrão de forma tal que sejam incorporados termos de massa para os neutrinos, e encontrar um mecanismo que explique o valor das massas observadas. É quase um consenso que o mecanismo See-Saw proporciona a mais elegante explicação para o valor observado das massas dos neutrinos. Neste trabalho implementamos o mecanismo See-Saw no modelo 3-3-1 com neutrinos de mão direita, 3 - 3 - 1RHV. A implementação é feita com a introdução de um sexteto escalar e a quebra espontânea do número leptônico. Identificamos o Majoron como um singleto pelo grupo SU(2)LNU(1)y, o que o torna seguro sob os atuais limites dos dados eletrofracos. O principal resultado deste trabalho é que o mecanismo See-Saw funciona na escala dos TeVs, e como resultado a massa dos neutrinos de m~ao direita encontra-se na escala eletrofraca, fornecendo uma grande oportunidade de testar a sua existência nos atuais detectores. Finalmente, apresentamos uma das propriedades mas interessantes do modelo, a troca de sabor na corrente neutra (FCNC). Mostramos a forma explícita desta lagrangiana e motivamos o estudo deste fenômeno por meio de interações hadrônicas e leptônicas que possibilitam sua testabilidade na próxima geração de aceleradores.

Submitted by FAGNER CINTRA CORREIA null (ccorreia@ift.unesp.br) on 2017-09-24T14:11:35Z No. of bitstreams: 1 Correia_TeseIFT.pdf: 861574 bytes, checksum: 1829fcb0903e20303312d37d7c1e0ffc (MD5) / Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-09-27T19:37:47Z (GMT) No. of bitstreams: 1 correia_fc_dr_ift.pdf: 861574 bytes, checksum: 1829fcb0903e20303312d37d7c1e0ffc (MD5) / Made available in DSpace on 2017-09-27T19:37:47Z (GMT). No. of bitstreams: 1 correia_fc_dr_ift.pdf: 861574 bytes, checksum: 1829fcb0903e20303312d37d7c1e0ffc (MD5) Previous issue date: 2017-07-27 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O Modelo Padrão Efetivo é apresentado como um método consistente de parametrizar Física Nova. Os conceitos de Matching e Power Counting são tratados, assim como a Expansão em Derivadas Covariantes introduzida como alternativa à construção do conjunto de operadores efetivos resultante de um modelo UV particular. A técnica de integração funcional é aplicada em casos que incluem o MP com Tripleto de Escalares e diferentes setores do modelo 3-3-1 na presença de Leptons pesados. Finalmente, o coeficiente de Wilson de dimensão-6 gerado a partir da integração de um quark-J pesado é limitado pelos valores recentes do parâmetro obliquo Y. / It will be presented the principles behind the use of the Standard Model Effective Field Theory as a consistent method to parametrize New Physics. The concepts of Matching and Power Counting are covered and a Covariant Derivative Expansion introduced to the construction of the operators set coming from the particular integrated UV model. The technique is applied in examples including the SM with a new Scalar Triplet and for different sectors of the 3-3-1 model in the presence of Heavy Leptons. Finally, the Wilson coefficient for a dimension-6 operator generated from the integration of a heavy J-quark is then compared with the measurements of the oblique Y parameter. / CNPq: 142492/2013-2 / CAPES: 88881.132498/2016-01

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-05-08T00:11:48Z No. of bitstreams: 1 NAYARA BRANDÃO DE FREITAS – DISSERTAÇÃO (PPGEE) 2016.pdf: 3718233 bytes, checksum: f4f88b8a316139fc246558ded5f688d9 (MD5) / Made available in DSpace on 2018-05-08T00:11:48Z (GMT). No. of bitstreams: 1 NAYARA BRANDÃO DE FREITAS – DISSERTAÇÃO (PPGEE) 2016.pdf: 3718233 bytes, checksum: f4f88b8a316139fc246558ded5f688d9 (MD5) Previous issue date: 2016-06-23 / O tema desenvolvido consiste no estudo, caracterização e análise de conversores multiníveis CA/CC/CA monofásicos/monofásicos, monofásicos/bifásicos e monofásicos/trifásicos aplicados a sistemas de conversão e compensação de energia, empregando IGBTs (Transistor Bipolar de Porta isolada) como dispositivos semicondutores. No decorrer do trabalho, diversas topologias são analisadas e comparadas utilizados critérios como quantidade de barramentos CC, valores das tensões dos barramentos CC, WTHD (Distorção Harmônica Total Ponderada) das tensões chaveadas, frequências de chaveamentos dos IGBTs e perdas por condução e chaveamento. Os sistemas de controle das variáveis dos conversores estudados são apresentados e o controle individual dos barramentos CC é abordado com destaque. Implementações experimentais foram utilizadas para comprovar a teoria apresentada e mostrar a viabilidade dos sistemas. / This work consists in the study, characterization, anda analysis of AC/DC/AC multilevel converters are applied to conversion and compensation systems and employ and IGBTs (Insulated Gate Bipolar Transistor) as power semiconductor device. Many topologies are analyzed and compared considering the number of DC-links, DC-links voltages values, WTHDs (Weighted Total Harmonic Distortion) of the generated voltages, and semiconductors conduction and switching losses. The control systems of the studied converters are presented and the individual control of the DC-links voltages in highlighted. Experimental results are provided in order to prove the theoretical results and the viability of the systems.

Nesta dissertação apresentamos um método de quantização matemática e conceitualmente rigoroso para o campo escalar livre de interações. Trazemos de início alguns aspéctos importantes da Teoria de Distribuições e colocamos alguns pontos de geometria Lorentziana. O restante do trabalho é dividido em duas partes: na primeira, estudamos equações de onda em variedades Lorentzianas globalmente hiperbólicas e apresentamos o conceito de soluções fundamentais no contexto de equações locais. Em seguida, progressivamente construímos soluções fundamentais para o operador de onda a partir da distribuição de Riesz. Uma vez estabelecida uma solução para a equação de onda em uma vizinhança de um ponto da variedade, tratamos de construir uma solução global a partir da extensão do problema de Cauchy a toda a variedade, donde as soluções fundamentais dão lugar aos operadores de Green a partir da introdução de uma condição de contorno. Na última parte do trabalho, apresentamos um mínimo da Teoria de Categorias e Funtores para utilizar esse formalismo na contrução de um funtor de segunda quantização entre a categoria de variedades Lorentzianas globalmente hiperbólicas e a categoria de redes de álgebras C* satisfazendo os axiomas de Haag-Kastler. Ao fim, retomamos o caso particular do campo escalar quântico livre. / In this thesis we present a both mathematical and conceptually rigorous quantization method for the neutral scalar field free of interactions. Initially, we introduce some aspects of the Theory of Distributions and we establish some points of Lorentzian geometry. The rest of the work is divided in two parts: in the first one, we study wave equations on globally hyperbolic Lorentzian manifolds, hence presenting the concept of fundamental solutions within the context of locally defined wave equations. Next, we progressively construct fundamental solutions for the wave operator from the Riesz distribution. Once established a solution to the wave equation in a neighbourhood of a point of the manifold, we move forward to produce a global solution from the extension of the Cauchy problem to the whole manifold. At this stage, fundamental solutions are replaced by Green\'s operators by the imposition of appropriate boundary conditions. In the last part, we present a minimum on the Theory of Categories and Functors. This is followed by the use of this formalism in the development of a second-quantization functor between the category of Lorentzian globally hyperbolic manifolds and the category of nets of C*-algebras obeying Haag-Kastler axioms. Finally, we turn our attention to the particular case of the quantum free scalar field.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / FundaÃÃo de Amparo à Pesquisa do Estado do Amazonas / Esta tese està composta de quatro partes distintas. Na primeira parte, vamos dar uma nova caracterizaÃÃo da esfera euclidiana como a Ãnica variedade Riemanniana compacta com curvatura escalar constante e admitindo um campo de vetores conforme nÃo trivial que à tambÃm Ricci conforme. Na segunda parte, provaremos algumas propriedades dos quase sÃlitons de Ricci, as quais permitem estabelecer condiÃÃes de rigidez desses objetos, bem como caracterizar as estruturas de quase sÃlitons de Ricci gradiente na esfera euclidiana. ImersÃes isomÃtricas tambÃm serÃo consideradas; classificaremos os quase sÃlitons de Ricci imersos em formas espaciais, atravÃs de uma condiÃÃo algÃbrica sobre a funÃÃo sÃliton. AlÃm disso, vamos caracterizar, atravÃs de uma condiÃÃo sobre o operador de umbilicidade, as hipersuperfÃcies n-dimensionais de uma forma espacial, com curvatura mÃdia constante, tendo duas curvaturas principais distintas e com multiplicidades p e n - p. Na terceira parte, provaremos um resultado de rigidez e algumas fÃrmulas integrais para uma mÃtrica m-quasi-Einstein generalizada compacta. Na Ãltima parte, vamos apresentar uma relaÃÃo entre a curvatura gaussiana e o Ãngulo de contato de superfÃcies imersas na esfera euclidiana tridimensional,a qual permite concluir que a superfÃcie à plana, se o Ãngulo de contato for constante. AlÃm disso, deduziremos que o toro de Clifford à a Ãnica superfÃcie compacta com curvatura mÃdia constante tendo tal propriedade. / This thesis is composed of four distinct parts. In the first part, we shall give a new characterization of the Euclidean sphere as the only compact Riemannian manifold with constant scalar curvature carrying a conformal vector eld non-trivial which is also Ricci conformal. In the second part, we shall prove some properties of almost Ricci solitons, which allow us to establish conditions for rigidity of these objects, as well as characterize the structures of gradient almost Ricci soliton in Euclidean sphere. Isometric immersions also will be considered, we shall classify almost Ricci solitons immersed in space forms, through algebraic condition on soliton function. Furthermore, we characterize under a condition of the umbilicity operator, n-dimensional hypersurfaces in a space form with constant mean curvature, admitting two distinct principal curvatures with multiplicities p and n - p. In the third part, we prove a result of rigidity and some integral formulae for a compact generalized m-quasi-Einstein metric. In the last part, we present a relation between the Gaussian curvature and the contact angle of surfaces immersed in Euclidean three-dimensional sphere, which allows us to conclude that such a surface is at provided its contact angle is constant. Moreover, we deduce that Clifford tori are the unique compact surfaces with constant mean curvature having such property.

Orientador: Pedro Cunha de Holanda / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-16T08:47:51Z (GMT). No. of bitstreams: 1 MedinaJaime_Miguel_M.pdf: 2665434 bytes, checksum: ff126a38e30aec81b803a8fdcddcbc96 (MD5) Previous issue date: 2010 / Resumo: Neste trabalho apresentamos um estudo de alguns problemas que ainda não forem esclarecidos na física de neutrinos do modelo padrão (MP) e encaminhamos eles na direção de física nova. Para esse fim, estuda-se uma classe de extensões de Gauge quirais do MP com simetria SU(3)C x SU(3)L x U(1)X (modelos 331), onde estudamos a interação eletrofraca dos neutrinos com a matéria via correntes carregadas e neutras (CC e CN) através dos bósons Gauge do modelo para processos de espalhamento elástico coerente. Finalmente, encontramos vínculos entre as contribuições não padrão no modelo 331 com as interações não padrão (INP) em experimentos de seção de choque, onde encontramos que o modelo 331 apresenta INP diagonais universais da ordem e a M2 W,Z / M2 X <~ O(10-3). Mostramos que o valor esperado no vácuo (VEV) para o tão procurado bóson de Higgs neste modelo tem que ser ?2 <~174.105GeV e os VEV V > 1.3TeV e 142 GeV < ?1 < 201GeV. Os novos bósons do modelo deverão ter massas maiores a 610 GeV / Abstract: We present a study of some problems that are not yet clarified in Standard Model (SM) neutrino physics and guide them in the direction of new physics. To this aim, we study a class of extensions of the SM Gauge chiral symmetry SU(3)CSU(3)LU(1)X (331 model), where we study the electroweak interaction of neutrinos with matter via charged and neutral current (CC and NC) by the gauge bosons of the model for coherent elastic scattering process. We finally found connections between the non-standard contributions on 331 with non-standard interactions (NSI) in cross section experiments, where we find that the model 331 has diagonal universal NSI of order e a M2 W,Z / M2 X <~ O(10-3) . We show that the expected value in vacuum (VEV) for the quite searched Higgs boson in this model has to be ?2 <~174.105 GeV and the VEV V > 1.3TeV and 142 GeV < ?1 < 201 GeV. The new bosons of the model must have masses greater than 610 GeV / Mestrado / Física das Particulas Elementares e Campos / Mestre em Física

Level sets are extensively used for the visualization of scalar fields. The Reeb graph of a scalar function tracks the evolution of the topology of its level sets. It is obtained by mapping each connected component of a level set to a point. The Reeb graph and its loop-free version called the contour tree serve as an effective user interface for selecting meaningful level sets and for designing transfer functions for volume rendering. It also finds several other applications in the field of scientific visualization. In this thesis, we focus on designing algorithms for efficiently computing the Reeb graph of scalar functions and using the Reeb graph for effective visualization of scientific data. We have developed three algorithms to compute the Reeb graph of PL functions defined over manifolds and non-manifolds in any dimension. The first algorithm efficiently tracks the connected components of the level set and has the best known theoretical bound on the running time. The second algorithm, utilizes an alternate definition of Reeb graphs using cylinder maps, is simple to implement and efficient in practice. The third algorithm aggressively employs the efficient contour tree algorithm and is efficient both theoretically, in terms of the worst case running time, and practically, in terms of performance on real-world data. This algorithm has the best performance among existing methods and computes the Reeb graph at least an order of magnitude faster than other generic algorithms. We describe a scheme for controlled simplification of the Reeb graph and two different graph layout schemes that help in the effective presentation of Reeb graphs for visual analysis of scalar fields. We also employ the Reeb graph in four different applications – surface segmentation, spatially-aware transfer function design, visualization of interval volumes, and interactive exploration of time-varying data. Finally, we introduce the notion of topological saliency that captures the relative importance of a topological feature with respect to other features in its local neighborhood. We integrate topological saliency with Reeb graph based methods and demonstrate its application to visual analysis of features.

Le biofilm épilithique (anciennement périphyton), agrégat phototrophe d’organismes se développant sur le fond des cours d’eau, joue un rôle essentiel dans le fonctionnement des hydroécosystèmes fluviaux comme la Garonne. Pour améliorer la modélisation à l’échelle du tronçon de rivière de ces systèmes, il est nécessaire de prendre en compte les caractéristiques locales de l’écoulement notamment pour la prédiction de l’évolution de la biomasse. Les méthodes expérimentales actuelles ne permettent pas d’accéder aux grandeurs hydrodynamiques locales proches du fond rugueux, dans la zone dite de ’canopée’. Le travail présenté ici vise donc à compléter ces résultats par des simulations numériques directes, avec une méthode de frontières immergées, d’écoulements turbulents de couche limite hydrauliquement rugueuse formée d’hémisphères. L’objectif est double : il s’agit d’une part de mettre en relation les motifs de colonisation et la croissance du biofilm observés expérimentalement aux caractéristiques locales de l’écoulement, et d’autre part, de quantifier les flux d’espèces chimiques entre la canopée et la pleine eau et ce, en fonction du type d’arrangement des obstacles formant le fond, du confinement et du nombre de Reynolds rugueux. Après avoir validé la méthode numérique sur des cas proches de ceux rencontrés dans les expériences, et vérifié que les grandeurs hydrodynamiques moyennes et turbulentes dans la pleine eau sont en bon accord avec les résultats expérimentaux, plusieurs campagnes de simulations ont été réalisées pour deux types d’arrangements du fond (aligné et décalé), plusieurs confinements et une gamme de nombre de Reynolds rugueux représentatifs des écoulements en rivière. Ce travail a pu mettre en évidence que le biofilm colonise préférentiellement les zones de faible cisaillement local et un critère de colonisation a été déterminé. Des simulations avec transfert d’espèce chimique ont été réalisées pour différentes valeurs du nombre de Schmidt et ont permis de quantifier les flux d’échange en fonction de ce paramètre. / The epilithic biofilm, aggregate set of phototrophic organisms growing on the bed of rivers, plays an essential role in the functioning of hydro-ecosystems such as the Garonne river. To improve the modeling of these systems it is necessary to take into account the local conditions in the region close to the rough bottom, named ’canopy’. Direct numerical simulations with a immersed boundary method are used to simulate turbulent boundary layer flows with a rough wall composed of hemipheres. The aim of these simulations is twofold : (1) investigate the influence of local flow conditions on the biofilm colonization and growth processes and (2) quantify the transfers of chemical species between the canopy region and the main water column, for various hemispheres arrangement, confinement and turbulent Reynolds number encountered in natural rivers. This work allowed to show that biofilm colonization first occurs in low-to-moderate local shear stress at the hemisphere surface. Simulations with the transport of a passive scalar were performed for various Schmidt number, and gave an estimation of the mass fluxes as a function of this parameter.

The Standard Model (SM) of particle physics provides the theoretical framework to describe the fundamental interactions among elementary constituents of matter. SM is supported by experiments to a high degree of accuracy, up to parts per-mil for the electroweak (EW) sector and parts-per-trillion for QED alone, but it still remains incomplete. Many observed phenomena lack explanation in the framework of the SM and its particles. They indicate the possibility of existence of particles and interactions beyond the SM (BSM). These phenomena include dark matter (DM), dark energy and baryonic asymmetry of the universe. In addition, a quantum description of gravity is still lacking. The top quark has the largest mass among the SM particles. Due to it’s heavy mass, top quark is the only colored particle which does not hadronize and hence its properties are directly accessible by studying it’s decay particles. The order one Yukawa coupling of the top quark also imbibes it with an important role in the behavior of the SM couplings at higher energy scales where possible BSM physics may contribute. As a result, precision measurements of top quark properties may provide a glimpse into BSM physics and hence making these measurements is one of the core aims of the Large Hadron Collider. In stark contrast with top quark physics is the elusive, dark matter (DM) of the universe. There exists a lot of observational evidence for it but, as of yet, with no clue with regards to its particle properties and interactions. Compelling evidence for the existence of DM comes from measurements based on cosmic microwave background radiation, astrophysical observations of distribution of visible matter in galaxy clusters, galactic cluster collisions (e.g. bullet cluster), gravitational lensing, galactic rotation curves, structure formation simulations, to name a few. It is interesting to investigate the possibility that there may be a connection between top quark and DM. In this thesis, we extend the SM with simplified models to study BSM physics at colliders and also to explain the DM puzzle. Here, we use the Top quark as a laboratory for constructing generic probes of BSM and also of the dark sector physics. In Chapter 1, we introduce some relevant background and salient aspects of the SM framework on which the following BSM theories are built. In Chapter 2 we explore an s channel and a t-channel simplified model in the context of top quark pair production using asymmetries constructed with kinematic variables of the top decay products. In Chapter 3, we then propose a simplified model which includes a colored scalar as the mediator between DM and SM particles, termed gluphillic scalar dark matter (GSDM). Monojet process is one of the primary channels to probe DM at hadron colliders. In Chapter 3, the discussion of monojet process at the Large Hadron Collider (LHC) is limited to the effective field theory (EFT) framework. In Chapter 4 we discuss collider processes in GSDM model with complete loop calculations for the diagrams involving the mediating colored scalar. We also compare the loop calculation with the EFT results to find the range of applicability of the EFT. The top quark study in Chapter 2 was initially inspired from an interesting observation made in 2008 which suggested a deviation from the SM in the forward-backward asymmetry (FBA) of a pair produced top quark. The value of FBA measured at the time was 18% ±12%. This value deviated by more than 1σ with respect to the SM leading order (LO) value of 5%. The deviation was observed by both the detectors at Tevatron, D0 and CDF, and it’s significance increased with additional data in 2012. Recent analyses of the data by D0 is now in better agreement with the latest effective-NNNLO calculations. However, the FBA measurements by CDF are still in tension with those by D0 and the value predicted by theoretical calculations. Inspired by this puzzle, which may be on its way to getting solved, we have been able to construct effective probes of BSM physics for the on-going and future searches of BSM in the top quark sector. In our analyses, we studied correlations among observables which can distinguish between different sources of BSM contributions in the top quark pair production. As a template, we use an s-channel and a t-channel mediator, both of which leave very different signatures in the kinematic asymmetry correlations. The simplified models considered by us also included parity breaking interactions which lead to polarized top quarks, providing another probe into the underlying production process. We find that all the kinematic distributions of the decay lepton get influenced by the polarization of the top quark. We show that these correlations can distinguish well between the template models of axigluon and diquark. In general, all of these observables also provide a probe into the polarization of the top quark and therefore any chiral couplings with the mediator. However, the lepton polar angle asymmetry measured in the lab frame is special in that it can not only probe the longitudinal polarization as other observables but is also sensitive to the transverse polarization of the top quark. We also show the effectiveness of the proposed top quark kinematic observables, to distinguish between s and t-channel BSM physics models, in future searches for BSM particles at the run-II LHC. In a large verity of dark matter (DM) models the simplest candidate is the model of a singlet scalar particle. The scalar may couple to the standard model in a number of ways via any of the SM particles. Such models with BSM Yukawa interactions or gauge sector extensions are strongly constrained from both the direct detection and collider precision measurements. The remaining models either predict a very heavy dark matter, completely out of reach of collider searches or introduce an unnaturally weak coupling with the SM particles giving no justifications for the small numbers. An interesting corner of the space of possible DM models which has been under-explored so far includes interactions of DM particles with gluons. Although DM particles cannot themselves be charged or colored, a colored scalar mediator can allow this interaction. One such model arises when we consider the scalar DM in presence of a colored scalar particle, for example the one from t-channel model above. Such colored scalars are generically present in a number of BSM theories including SUSY and GUT. How-ever, without the need for any additional gauge symmetries, the two scalars would interact with each other via the marginal operators. In Chapter 3 we study a SM singlet scalar DM candidate which couples to SM via a colored scalar particle. In the GSDM model, DM and mediator interact via the quartic, marginal operator. DM annihilation cross-section of the order of weak interactions (∼ 0.1pb) is predicted to explain the observed dark matter relic density if arising from thermal production of a WIMP DM candidate of mass ∼ 100 GeV. On investigating the GSDM model, we find that it allows a large annihilation cross-section and is still compatible with direct detection bounds. This is so because the annihilation cross-section to a pair of colored scalars proceeds via a tree-level interaction, whereas the interaction with SM particles proceeds via loop diagrams involving the colored scalars. Our work shows that this model is compatible with the observed relic density of DM when the mediating particle is lighter than DM for a large range of the couplings. For masses of the DM and the mediator less then ∼ 50 GeV, the DM can also be lighter than the mediator where the annihilation then proceeds via loop interactions. This region of parameter space is strongly constrained from the collider physics bounds on a colored scalar particle. These bounds become much weaker in the case where the colored scalar does not couple to quarks and hence cannot decay. The bounds coming from long-lived colored scalars become relevant in those cases and also constrain the light mass window. A colored scalar interacting with quarks must do so without violating the strong flavor constraints. We consider the scalar in the framework of a class of models termed minimally flavor violating (MFV) and also assume that it couples only to the right handed up-sector quarks. Such a particle would couple to the top quark and would be observable at the LHC pair production of the top quark. We find constraints on a color triplet particle in such a case and show the coupling and mass regions allowed. Constraints from the decays to light quarks are interpreted from dijet process searches and limit the mass of a color-triplet scalar above 350 GeV. The primary process for direct search of stable particles produced at a collider is a single jet in association with missing transverse energy (MET). We find that in an effective field theory (EFT) framework, very weak bounds are obtained on the mediating scale. In Chapter 4, we perform complete loop calculations for processes involving colored scalar particles and DM at LHC in order to explore the GSDM model at LHC and FCC (Future Circular Collider). The EFT is valid only for mediator masses much heavier than the momentum transfer or the MET cuts. We show the region of applicability of the EFT by comparing it with respect to the loop induced calculation. We analyze the monojet + missing transverse energy (MET) process to find the expected bounds from LHC 13 TeV run-II. We calculate the reach of the LHC in the high luminosity run in the future and also the reach of the FCC to explore the GSDM model. We perform all our calculations for a number of representations of the colored mediator from a triplet to dimension 15. As expected, collider constraints are only significant when the dark matter is light enough (mDM ∼ 10 GeV) to be copiously produced at the LHC. We find that in the high luminosity run, LHC can probe the scalar triplet particle up-to 50 GeV mass in the monojet process though a dimension 15 particle can be probed up to 150 GeV. With an order of magnitude higher beam energy, FCC can rule out much larger parameter space or provide observational evidence for TeV scale mediating particles. In conclusion, this thesis adds to the growing body of literature which points towards BSM discoveries around the corner at high luminosity LHC in the top physics and in dark sector physics. We have also proposed avenues for precision BSM studies at the next generation colliders.

Avec le développement des communications et de l'Internet, l'échange des informations cryptées a explosé. Cette évolution a été possible par le développement des protocoles de la cryptographie asymétrique qui font appel à des opérations arithmétiques telles que l'exponentiation modulaire sur des grands entiers ou la multiplication scalaire de point de courbe elliptique. Ces calculs sont réalisés par des plates-formes diverses, depuis la carte à puce jusqu'aux serveurs les plus puissants. Ces plates-formes font l'objet d'attaques qui exploitent les informations recueillies par un canal auxiliaire, tels que le courant instantané consommé ou le rayonnement électromagnétique émis par la plate-forme en fonctionnement.Dans la thèse, nous améliorons les performances des opérations résistantes à l'attaque Simple Power Analysis. Sur l'exponentiation modulaire, nous proposons d'améliorer les performances par l'utilisation de multiplications modulaires multiples avec une opérande commune optimisées. Nous avons proposé trois améliorations sur la multiplication scalaire de point de courbe elliptique : sur corps binaire, nous employons des améliorations sur les opérations combinées AB,AC et AB+CD sur les approches Double-and-add, Halve-and-add et Double/halve-and-add et l'échelle binaire de Montgomery ; sur corps binaire, nous proposons de paralléliser l'échelle binaire de Montgomery ; nous réalisons l'implantation d'une approche parallèle de l'approche Right-to-left Double-and-add sur corps premier et binaire, Halve-and-add et Double/halve-and-add sur corps binaire. / The development of online communications and the Internet have made encrypted data exchange fast growing. This has been possible with the development of asymmetric cryptographic protocols, which make use of arithmetic computations such as modular exponentiation of large integer or elliptic curve scalar multiplication. These computations are performed by various platforms, including smart-cards as well as large and powerful servers. The platforms are subject to attacks taking advantage of information leaked through side channels, such as instantaneous power consumption or electromagnetic radiations.In this thesis, we improve the performance of cryptographic computations resistant to Simple Power Analysis. On modular exponentiation, we propose to use multiple multiplications sharing a common operand to achieve this goal. On elliptic curve scalar multiplication, we suggest three different improvements : over binary fields, we make use of improved combined operation AB,AC and AB+CD applied to Double-and-add, Halve-and-add and Double/halve-and-add approaches, and to the Montgomery ladder ; over binary field, we propose a parallel Montgomery ladder ; we make an implementation of a parallel approach based on the Right-to-left Double-and-add algorithm over binary and prime fields, and extend this implementation to the Halve-and-add and Double/halve-and-add over binary fields.