This thesis comes in three main parts. In the first of these (comprising chapters 2 - 6), the basic theory of Riemannian and conformal submersions is described and the relevant geometric machinery explained. The necessary Clifford algebra is established and applied to understand the relationship between the spinor bundles of the base, the fibres and the total space of a submersion. O'Neill-type formulae relating the covariant derivatives of spinor fields on the base and fibres to the corresponding spinor field on the total space are derived. From these, formulae for the Dirac operators are obtained and applied to prove results on Dirac morphisms in cases so far unpublished. The second part (comprising chapters 7-9) contains the basic theory and known classifications of G2-structures and Spin+ 7 -structures in seven and eight dimensions. Formulae relating the covariant derivatives of the canonical forms and spinor fields are derived in each case. These are used to confirm the expected result that the form and spinorial classifications coincide. The mean curvature vector of associative and Cayley submanifolds of these spaces is calculated in terms of naturally-occurring tensor fields given by the structures. The final part of the thesis (comprising chapter 10) is an attempt to unify the first two parts. A certain `7-complex' quotient is described, which is analogous to the well-known hyper-Kahler quotient construction. This leads to insight into other possible interesting quotients which are correspondingly analogous to quaternionic-Kahler quotients, and these are speculated upon with a view to further research.

Almost contact metric submersions constitute a class of Riemannian submersions whose total space is an almost contact metric manifold. Regarding the base space, two types are studied. Submersions of type I are those whose base space is an almost contact metric manifold while, when the base space is an almost Hermitian manifold, then the submersion is said to be of type II. After recalling the known notions and fundamental properties to be used in the sequel, relationships between the structure of the fibres with that of the total space are established. When the fibres are almost Hermitian manifolds, which occur in the case of a type I submersions, we determine the classes of submersions whose fibres are Kählerian, almost Kählerian, nearly Kählerian, quasi Kählerian, locally conformal (almost) Kählerian, Gi-manifolds and so on. This can be viewed as a classification of submersions of type I based upon the structure of the fibres. Concerning the fibres of a type II submersions, which are almost contact metric manifolds, we discuss how they inherit the structure of the total space. Considering the curvature property on the total space, we determine its corresponding on the fibres in the case of a type I submersions. For instance, the cosymplectic curvature property on the total space corresponds to the Kähler identity on the fibres. Similar results are obtained for Sasakian and Kenmotsu curvature properties. After producing the classes of submersions with minimal, superminimal or umbilical fibres, their impacts on the total or the base space are established. The minimality of the fibres facilitates the transference of the structure from the total to the base space. Similarly, the superminimality of the fibres facilitates the transference of the structure from the base to the total space. Also, it is shown to be a way to study the integrability of the horizontal distribution. Totally contact umbilicity of the fibres leads to the asymptotic directions on the total space. Submersions of contact CR-submanifolds of quasi-K-cosymplectic and quasi-Kenmotsu manifolds are studied. Certain distributions of the under consideration submersions induce the CR-product on the total space. / Mathematical Sciences / D. Phil. (Mathematics)

Almost contact metric submersions constitute a class of Riemannian submersions whose total space is an almost contact metric manifold. Regarding the base space, two types are studied. Submersions of type I are those whose base space is an almost contact metric manifold while, when the base space is an almost Hermitian manifold, then the submersion is said to be of type II. After recalling the known notions and fundamental properties to be used in the sequel, relationships between the structure of the fibres with that of the total space are established. When the fibres are almost Hermitian manifolds, which occur in the case of a type I submersions, we determine the classes of submersions whose fibres are Kählerian, almost Kählerian, nearly Kählerian, quasi Kählerian, locally conformal (almost) Kählerian, Gi-manifolds and so on. This can be viewed as a classification of submersions of type I based upon the structure of the fibres. Concerning the fibres of a type II submersions, which are almost contact metric manifolds, we discuss how they inherit the structure of the total space. Considering the curvature property on the total space, we determine its corresponding on the fibres in the case of a type I submersions. For instance, the cosymplectic curvature property on the total space corresponds to the Kähler identity on the fibres. Similar results are obtained for Sasakian and Kenmotsu curvature properties. After producing the classes of submersions with minimal, superminimal or umbilical fibres, their impacts on the total or the base space are established. The minimality of the fibres facilitates the transference of the structure from the total to the base space. Similarly, the superminimality of the fibres facilitates the transference of the structure from the base to the total space. Also, it is shown to be a way to study the integrability of the horizontal distribution. Totally contact umbilicity of the fibres leads to the asymptotic directions on the total space. Submersions of contact CR-submanifolds of quasi-K-cosymplectic and quasi-Kenmotsu manifolds are studied. Certain distributions of the under consideration submersions induce the CR-product on the total space. / Mathematical Sciences / D. Phil. (Mathematics)

La ville du Havre et son agglomération sont implantées entre l'estuaire de la Seine et le plateau crayeux du Pays de Caux. Ce territoire côtier est soumis à des risques naturels typiques des zones littorales que sont les submersions marines et l'érosion des falaises. L'étude a été réalisée à partir de photographies aériennes et de relevés topographiques aériens LiDAR (laser altimétrique). Elle a visé à cartographier les zones de débordement et d'inondations historiques (1981, 1983 et 1984) et potentielles de la ville basse du Havre en superposant divers scenarii de niveaux d'eaux statiques et la topographie haute précision de la zone urbaine. Les falaises littorales de la pointe de Caux, situées entre le Cap de La Hève et le Cap d'Antifer subissent une dynamique gravitaire à mouvements de terrain récurrents. L'étude de la zone entre 1985 et 2008 (23 ans) montre un taux d'érosion moyen du haut de falaise de 18 cm/an. L'accumulation de dépôts d'éboulis a formé un talus continu en pied de falaise qui atteint un volume de 36,7 millions de m3. Les dépôts d'éboulis sont localement très variables en taille, volume et composition, du nord au sud du secteur d'étude et n’est atteint que sur 10 % du linéaire étudié lors des hautes mers de vive-eau. L'impact d'une augmentation du niveau marin au Havre (1,6 à 2,4 mm/an) est susceptible d'amplifier à long terme l'intensité de ces deux aléas côtiers, mais il apparaît cependant comme faible par rapport à l'influence des facteurs météorologiques. / Le Havre suburb is located between the Seine estuary and the chalk plateau of the Paris basin NW boundary. This coastal territory is submitted to typical natural hazards observed on coastal areas that are coastal floods and cliffs erosion. The study use data from aerial photographs and LiDAR surveys. The lower part of Le Havre town, built around historical tidal docks, is sensitive to coastal floods hazard. Three urban coastal floods occurred in 1981, 1983 and 1984 resulting to a combination between high water level of spring tides and surges produced by low air pressure and/or strong winds. The aim is to map, in the lower part of Le Havre town, the areas of potential overflow and flood. Different scenarii of static water levels have been applied on the accurate urban topography from LiDAR. Coastal cliffs, located between La Hève and Antifer Capes, showed recurrent gravitational movements. On the period 1985-2008 (23 years), the cliff top shows an average erosion rate of 18 cm/yr. The accumulation of sedimentary instabilities had formed a continuous wedge of 36.7 million m3. The wedge deposits are very variable in size, volume and nature, from north to south. At Le Havre, the impact of the sea-level rise may amplify, in long-term scale, the intensity of these two coastal hazards. However, the SLR impact appears to be low compared to the influence of meteorological factors.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Esta tese teve dois objetos de estudo: propriedades estocÃsticas em uma variedade Riemanniana, a saber, Completude EstocÃstica, Parabolicidade e propriedade Feller, e a geometria do tensor de Bakry-Emery. Na primeira parte da tese estudamos tais propriedades estocÃsticas no contexto de submersÃes Riemannianas e imersÃes isomÃtricas, tendo como ponto de partida o trabalho de Pigola e Setti [28] sobre a propriedade Feller. No nosso primeiro resultado, provamos que se uma imersÃo isomÃtrica em uma variedade Cartan-Hadamard possui vetor curvatura mÃdia com norma limitada entÃo a imersÃo à Feller. Um anÃlogo desse resultado jà era conhecido para o caso de completude estocÃstica [30]. Em seguida estabelecemos condiÃÃes necessÃrias e suficientes para que uma submersÃo seja estocasticamente completa (respec. parabÃlica), a saber, se uma submersÃo Riemanniana tem fibra mÃnima e o espaÃo total à estocasticamente completo (respec. parabÃlico) entÃo a base à estocasticamente completa (respec. parabÃlica). Reciprocamente, se a submersÃo Riemanniana tem fibra mÃnima e compacta e a base à estocasticamente completa (respec. parabÃlica) entÃo o espaÃo total à estocasticamente completo (respec. parabÃlico). Finalmente provamos que uma submersÃo Riemanniana tem fibra mÃnima e compacta entÃo o espaÃo total Âe Feller, se, e somente se, a base à Feller. Na segunda parte desta tese estudamos o tensor de Bakry-Emery Ricci, Ricf, que à uma extensÃo, no caso de variedades ponderadas, do tensor de Ricci. Estudamos a seguinte situaÃÃo: Ricci ≥ -cG, onde c à uma constante positiva e G ≥ O à uma funÃÃo suave. Esta limitaÃÃo nos permitiu obter algumas consequencias geomÃtricas e topolÃgicas, que passamos a descrever. Seja Mf uma variedade Riemanniana ponderada e po Є Mf fixado. Nosso primeiro resultado à uma estimativa superior, fora da bola geodÃsica de raio ro, para o Laplaciano ponderado da funÃÃo distÃncia r ao ponto po, mf, em termos da integral da funÃÃo G. A primeira consequÃncia dessa estimativa à uma estimativa para o volume ponderado Volf (B(R)) de uma bola geodÃsica de raio R em termos da integral da funÃÃo G. A estimativa de mf, juntamente com a hipÃtese de Æ ser radial e Әr Æ ≥ -a,a ≥ 0 (ou | Æ|≤ k) tambÃm nos permite demonstrar um teorema de comparaÃÃo entre mf e maG, Laplaciano da funÃÃo distÃncia no modelo de curvatura aG, bem como um teorema de comparaÃÃo entre o volume ponderado de uma bola geodÃsica de raio R em Mf, VolÆ(B(R)), e o volume da bola geodÃsica de raio R no modelo MaG, de curvatura aG. Utilizando uma versÃo ponderada da fÃrmula de Bochner provamos que, se Ricci ≥ Gâ entÃo Mf satisfaz o princÃpio do mÃximo de Omori-Yau, onde G à funÃÃo suave, positiva, nÃo decrescente e tal que G-1 nÃo à integrÃvel. Em particular concluÃmos que Mf à estocasticamente completa. O prÃximo resultado que obtivemos estende, para o tensor Ricf, um teorema de Myers devido a Ambrose [1]. Para tanto, uma hipÃtese sobre a funÃÃo Æ foi necessÃria. Como aplicaÃÃo, estendemos um resultado de compacidade de Ricci solitons de Fernando-Lopes e Garcia-Rio [15]. Em 1976, Yau [36] provou uma estimativa para o gradiente de uma funÃÃo u, positiva, harmÃnica em B(2R), no caso de M ser completa e Ricf ≥ -k, k ≥ 0. Tal estimativa depende apenas de R e k e foi estendida, no caso ponderado, para funÃÃes f harmÃnicas positivas, supondo Ricf ≥ -k e Ric ≥ -H, k, H ≥ 0. Bringhton [9] obteve estimativas para o gradiente de uma funÃÃo *-harmÃnica positiva utilizando somente a hipÃtese Ricf ≥ -k. As estimativas que obtivemos estendem as estimativas citas acima e, no caso em que Æ=G=0 resultam na estimativa original de Yau. Finalmente, provamos um teorema de comparaÃÃo entre o primeiro autovalor de Dirichlet da bola geodÃsica de raio R em Mf e o primeiro autovalor de Dirichlet da bola geodÃsica de raio MG. Tal resultado estende, para o caso ponderado, um resultado de Bessa e Montenegro [4]. / In this thesis we studied two objects(?): properties in Riemannian manifolds, more precisely stochastic completeness, parabolicity and the Feller property and geometric properties of Bakry Emery Ricci tensor. First, we studied such stochastic properties on Riemannian and isometric immersions. The initial motivation was the work of Pigola and Setti [30] about the Feller property. In our first result, we proved that if a isometric immersion on a Cartan-Hadamard manifold has bounded mean curvature vector then the immersion is Feller. An analogous result was know for stochastic completeness. After we stabilish necessary and sufficient conditions to a Riemannian submersion be stochastically complete (parabolic). More precisely if a Riemannian submersion has minimal fiber and the total space is stochastically complete (parabolic ) then the basis is also stochastically complete ( parabolic ). Conversely, if the Riemannian submersion has compact minimal fiber and the basis is stochastically complete ( parabolic, Feller ) then the total space also is. We also proved that if a Riemannian submersion has compact minimal fiber then the total space is Feller if, and only if the the basis is Feller. In the second part we studied the Barkry Emery Ricci tensor Ricf, wich is a natural extension of the Ricci tensor in the context of weighted manifolds. We studied the following: suppose that Ricf has a lower bound âcG where G is a smooth nonnegative function and c a positive constant. Such lower bound allow us to obtain some geometric and topological consequences as we describe below. Consider Mf a weighted Riemannian manifold. The first consequence is an upper estimate, outside a geodesic ball of radius r0, for the weighted Laplacian of the Riemannian distance in terms of the function G. Let Mf be a weighted Riemannian manifold and po Є Mf fixed. Our first result is an upper bound, outside of a geodesic ball of radius R centered in po, for the weighted Laplacian os the Riemannian distance function from po in terms od the function G. The first consequence of this estimate is an estimate for the weighted volume Volf (B(R)) of a geodesic ball with radius R in terms of the integral of G. This estimate together the assumption of f be radial and Ә f ≥ - a, a≥ 0 (or | f | ≤k ) allow us to prove a comparison theorem for mf e mag, the Laplacian of distance function of the Riemannian model fo curvature aG, as such as a comparison theoremfor the weighted volume of a geodesic ball with radius R on the Riemannian model MaG, with curvature aG. Using a weighted version of the Bochner formula we proved that Ricf ≥ Gâ then Mf satisfies the Omori-Yau Maximum Principle, where G is a positive, nondecreasing smooth function, such that G-1 does not belong to L1(Mf). In particular we conclude that Mf is stochastically complete. The next result we proved extends, for the tensor Ricf, a type Myers theorem due to Ambrose [1]. For this an additional assumption on f was required. As an aplication of this result we extended a result about compacity of Ricci solitons due to Fernandez-Lopez e GarcÃa-Rio [15]. In 1976, Yau [36] proved an estimate for the gradient of a positive harmonic funcion u, defined on B(2R), when M is complete and Ric ≥ -k, k≥ 0. Such estimate depends only on R and k and was extended, to the weighted, to the case, to f-harmonic positive functions, when Ricf ≥ - k and Ric ≥ - H, k, H ≥ 0. Brighton [9] obtained estimates for the gradient of a positive f-harmonic function assuming only Ricf ≥ -k. We obtained estimates for the case Ricf ≥ -G where G is a smooth nonnegative function and when f= G = 0 we recover the original estimate of Yau. Finally we proved a comparison theorem between the first eigenvalue of the geodesic ball of radius r on Mf and the first eigenvalue of the geodesic ball of radius r of the model MG. Such result extends, to the weighted case, a result due to Bessa e Montenegro [4].

Cette thèse présente l’étude de la signature sédimentaire des submersions marines de tempête, dans le domaine rétrolittoral. Cette signature peut être extrêmement variable principalement en fonction des paramètres météo-océaniques menant à la submersion, de la morphologie de l’avant-côte et du domaine rétrolittoral et du disponible sédimentaire. Premièrement, l’étude de dépôts de washover mis en place lors de l’hiver 2013-2014, au sud de l’île d’Oléron, particulièrement énergétique en terme de climat de vagues, via une approche couplant processus hydrodynamiques et sédimentologie, a permis (1) de mettre en évidence l’importance des ondes infragravitaires, sur une côte dissipative à caractère macrotidal, dans le déclenchement de l’overwash de la barrière et la mise en place de washovers ; et de (2) proposer un nouveau modèle de faciès des dépôts de washover mis en place par des ondes infragravitaires combinées à la marée haute. Deuxièmement, la caractérisation de la signature sédimentaire des submersions marines en domaine rétrolittoral plus distal a montré que dans le contexte morphologique des marais de Charente-Maritime, les apports extrêmement faibles de sédiments en provenance du domaine continental, entre deux évènements de submersion marine, empêche la distinction des différents niveaux de submersion. Cependant cette étude a permis de valider des proxies tels que la microfaune ou l’isotopie de la matière organique pour l’identification de niveaux de submersion marine, permettant en partie de pallier aux limites inhérentes à l’anomalie granulométrique généralement utilisée. Cette étude a aussi permis la mise en évidence d’une variabilité dans la signature sédimentaire des submersions marines entre deux marais géomorphologiquement contrastés et plus ou moins exposés aux houles en provenance de l’océan. / This thesis presents the study of the sedimentary signature of marine submersions triggered by storms, in the back barrier area. This signature can be extremely variable mainly according to the meteo-oceanic parameters leading to the submersion of the back barrier area, the morphology of the nearshore, shore and back barrier area, and sediment availability. Firstly, the study of washover deposits emplaced during the winter of 2013-2014 on the southern end of the Oléron Island, characterized by an exceptional wave climate, via a coupled hydrodynamical and sedimentological approach, allowed us to (1) highlight the importance of infragravity waves, on macrotidal and dissipative coasts, in triggering the overwash and emplace washover deposits ; and (2) to suggest a new facies model of washover deposits emplaced by infragravity waves combined to high tides. Secondly, the characterization of the sedimentary signature of marine submersions in the distal part of the back barrier area showed that in the morphological context of the Charente-Maritime coastal marshes, the extremely limited amounts of sediments in provenance from the continent, between two submersion events, prevent the distinction of the different marine submersion sedimentary layers. Nevertheless, this study allowed validating new proxies as microfauna and organic matter isotopy for the identification of marine submersion sedimentary signature, allowing to work independently of the granulometric anomaly proxy and its known limits. This study also allowed evidencing the variability in the sedimentary signature of marine submersions in geomorphologically contrasted marshes and that this variability was linked to the ocean waves exposure.

Orientadores: Alcibiades Rigas, Carlos Eduardo Duran Fernandez / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica / Made available in DSpace on 2018-08-20T13:56:12Z (GMT). No. of bitstreams: 1 Speranca_LlohamDallagnol_D.pdf: 994466 bytes, checksum: 472919d7eec0f563b673a0307450dc49 (MD5) Previous issue date: 2012 / Resumo: Nesse trabalho estudaremos a geometria e a topologia de algumas variedades homeomorfas, porém não difeomorfas, à esfera padrão Sn, chamadas esferas exóticas. Realizaremos duas dessas variedades como quocientes isométricos de fibrados principais com métricas de conexão sobre esferas de curvatura constante. Através disso, apresentaremos simetrias desses espaços e exemplos explícitos de difeomorfismos não isotópicos a identidade, usando-os para o cálculo de grupos de homotopia equivariante. Como mais uma aplicação dessa construção, provaremos que, se uma esfera homotópica de dimensão 15 é realizável como um fibrado linear sobre S8, então a mesma esfera é realizável como um fibrado linear sobre a esfera exótica de dimensão 8 com as mesmas funções de transição. No ultimo capítulo lidaremos com a geometria de fibrados induzidos, deduzindo uma condição necessária sobre a função indutora para que a métrica da conexão induzida tenha curvatura seccional não-negativa / Abstract: In this work we study the geometry and topology of manifolds homemorphic, but not diffeomorphic, to the standard sphere Sn, the so called exotic spheres. We realize two of these manifolds as isometric quotients of principal bundles with connection metrics over the constant curved sphere. Through this, we present symmetries in these spaces and explicit examples of diffeomorphisms not isotopic to the identity, using them for the calculation of equivariant homotopy groups. As another application, we prove that, if a homotopy 15-sphere is realizeble as the total space of a linear bundle over the standard 8-sphere, then, it is realizeble as the total space of a linear bundle over the exotic 8-sphere with the same transition maps. In the last chapter we deal with the geometry of pull-back bundles, deducing a necessary condition on the pull-back map for nonnegative curvature of the induced connection metric / Doutorado / Matematica / Doutor em Matemática

We describe a correspondence between two different links associated to the same K3 orbifold. This duality is produced when two elements, one inside and the other on the boundary of the Kähler cone, are identified. We call this correspondence ∂-duality. We also discuss the consequences of ∂-duality at the level of metrics. / Describimos una correspondencia entre dos enlaces asociados a un mismo espacio K3 que soporta a lo más, singularidades cíclicas de tipo orbifold. Esta dualidad se hace evidente cuando dos elementos, uno en el interior y el otro en la frontera del cono de Kähler, son identificados. Denominamos a esta correspondencia ∂-dualidad. También discutimos las consecuencias de ∂-dualidad al nivel de estructuras riemaniannas.

Un problema clásico en geometría lorentziana es la descripción de las inmersiones isométricas entre los espacios lorentzianos de curvatura constante. En este trabajo nos centramos en la clasificación de las inmersiones isométricas del plano lorentziano en el espacio anti-de Sitter tridimensional. Damos una fórmula de representación de estas inmersiones en términos de pares de curvas (con posibles singularidades) en el plano hiperbólico. Esto nos permite resolver los problemas propuestos por Dajczer y Nomizu en 1981. De entre todas las inmersiones isométricas del plano lorentziano en el espacio anti-de Sitter, algunas de ellas corresponden a toros lorentzianos (los ejemplos más sencillos son los toros de Hopf). Como aplicación de nuestra anterior descripción, probamos que todos estos toros pueden obtenerse a partir de dos curvas cerradas en el espacio hiperbólico. Finalmente, demostramos que los toros de Hopf son los únicos toros llanos lorentzianos inmersos en una amplia familia de sumersiones de Killing lorentzianas tridimensionales. / A classical problem in Lorentzian geometry is the description of the isometric immersions between Lorentzian spaces of constant curvature. We investigate the problem of classifying the isometric immersion from the Lorentz plane into the three-dimensional anti-de Sitter space, providing a representation formula of these isometric immersions in terms of pairs of curves (possibly with singularities) in the hyperbolic plane. We then give an answer to the open problems proposed by Dajczer and Nomizu in 1981. Among all isometric immersions of the Lorentz plane into the anti-de Sitter space, some of them are actually Lorentzian tori (the basic examples are the Hopf tori). As an application of our previous description, we prove that any such torus can be recovered from two closed curves in the hyperbolic plane. Finally, we prove that Lorentzian Hopf tori are the only immersed Lorentzian flat tori in a wide family of Lorentzian three-dimensional Killing submersions.

VASCONCELOS, Rosa Tayane de. O tensor de Ricci e campos de killing de espaços simétricos. 2017. 81 f. Dissertação (Mestrado em Matemática)- Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2017. / Submitted by Andrea Dantas (pgmat@mat.ufc.br) on 2017-09-18T13:45:50Z No. of bitstreams: 1 2017_dis_rtvasconcelos.pdf: 555452 bytes, checksum: 4ff6c8fb7950682913acabed03e9d3d7 (MD5) / Rejected by Rocilda Sales (rocilda@ufc.br), reason: Boa tarde, A Dissertação de ROSA TAYANE DE VASCONCELOS apresenta a alguns erros que devem corrigidos, os mesmos seguem listados abaixo: 1- EPÍGRAFE (coloque o nome do autor da epígrafe todo em letra maiúscula) 2- RESUMO/ ABSTRACT (retire o recuo dos parágrafos do resumo e do abstract) 3- PALAVRAS-CHAVE/ KEYWORDS (coloque a letra inicial do primeiro elemento das palavras- -chave e das Keywords em maiúscula) 4- CITAÇÕES (as citações a autores, que aparecem em todo o trabalho, não estão no padrão ABNT: se for apenas uma referência geral a uma obra, deve se colocar o último sobrenome do autor em letra maiúscula e o ano da publicação, ex.: EBERLEIN (2005). Caso seja a citação de um trecho particular da obra deve acrescentar o número da página, ex.: EBERLEIN (2005, p. 30). OBS.: as citações não devem estar entre colchetes. 5- TÍTULOS DOS CAPÍTULOS E SEÇÕES (coloque os títulos dos capítulos e seções em negrito) 6- REFERÊNCIAS (as referências bibliográficas não estão no padrão ABNT: apenas o último sobrenome do autor, que inicia a referência, deve estar em letra maiúscula, o restante do nome deve estar em letra minúscula. EX.: BROCKER, Theodor; TOM DIECK, Tammo. Representations of compact Lie groups, v. 98. Springer Science & Business Media, 2013. Atenciosamente, on 2017-09-18T15:04:06Z (GMT) / Submitted by Andrea Dantas (pgmat@mat.ufc.br) on 2017-09-19T13:33:40Z No. of bitstreams: 1 2017_dis_rtvasconcelos.pdf: 522079 bytes, checksum: ff99004fbe22e922f704a6a87365d3b6 (MD5) / Approved for entry into archive by Rocilda Sales (rocilda@ufc.br) on 2017-09-21T12:18:22Z (GMT) No. of bitstreams: 1 2017_dis_rtvasconcelos.pdf: 522079 bytes, checksum: ff99004fbe22e922f704a6a87365d3b6 (MD5) / Made available in DSpace on 2017-09-21T12:18:22Z (GMT). No. of bitstreams: 1 2017_dis_rtvasconcelos.pdf: 522079 bytes, checksum: ff99004fbe22e922f704a6a87365d3b6 (MD5) Previous issue date: 2017-09-13 / This work brings a smooth and self-contained introduction to the study of the most basic aspects of symmetric spaces, having as its nal goal the characterization of the Killing vector fields and of the Ricci tensor of such riemannian manifolds. Several of the results presented in the initial chapter are not easily found, in the Diferential Geometry literature, in a way as accessible and self-contained as here. This being said, we believe that this work embodies some didactic relevance, for it others students interested in symmetric spaces a relatively smooth first contact. We shall generally look at symmetric spaces as homogeneous manifolds G=H, where G is a Lie group and H is a closed Lie subgroup of G, such that the natural mapping : G ! G=H is a riemannian submersion. Ultimately, this map allows us to describe the relationships between the curvature, the Ricci tensor and the geodesics of G and G=H. For our purposes, the crucial remark is that, under appropriate circumstances, one guarantees the existence, in G=H, of a metric for which left translations are isometries. Hence, a one-parameter family of such isometries gives rise to a Killing vector field, which turn into a Jacobi vector eld when restricted to a geodesic. We present explicit expressions for such Jacobi vector elds, showing that they only depend on the eigenvalues of the linear operator TX : g ! g given by TX = (adX)2, for certain vector elds X 2 g. / Este trabalho traz uma introdução suave e autocontida ao estudo dos aspectos mais básicos de espaços simétricos, tendo como objetivo final a caracterização dos campos de Killing e do tensor de Ricci de tais variedades riemannianas. Vários dos resultados obtidos nos capítulos iniciais não são encontrados, na literatura de Geometria Diferencial, de maneira tão acessível e autocontida como apresentados aqui. Com isso, acreditamos que o trabalho reveste-se de alguma relevância didática, por oferecer aos alunos interessados no estudo de espaços simétricos um primeiro contato relativamente suave. Em linhas gerais, veremos espaços simétricos como variedades homogêneas G=H, onde G e um grupo de Lie e H um subgrupo de Lie fechado de G, tais que a aplicação natural: G ! G=H seja uma submersão riemanniana. Através dela, descrevemos relações entre a curvatura, o tensor de Ricci e as geodésicas de G e G=H. Para nossos propósitos, a observação crucial e que, sob certas hipóteses, garantimos a existência, em G=H, de uma métrica cujas translações a esquerda são isometrias. Portanto, uma família a um parâmetro de tais isometrias d a origem a um campo de Killing que, por sua vez, restrito a geodésicas torna-se um campo de Jacobi. Apresentamos expressões para esses campos de Jacobi, mostrando que os mesmos só dependem dos autovalores do operador linear TX : g ! g dado por TX = (adX)2, para certos campos X 2 g.