Orientadores: Luiz Antonio Barrera San Martin, Osvaldo Germano do Rocio / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica / Made available in DSpace on 2018-08-08T09:10:31Z (GMT). No. of bitstreams: 1 Verdi_MarcosAndre_D.pdf: 586732 bytes, checksum: c0182ba0a69107acd3d5548e682641df (MD5) Previous issue date: 2007 / Resumo:Neste trabalho estudamos dois problemas distintos: ações de semigrupos em órbitas adjuntas e compactificações de semigrupos. Quanto ao estudo das ações de semigrupos, consideramos um grupo de Lie semi-simples, não compacto, conexo e com centro finito G e a órbita adjunta de G através de elementos H pertencentes a uma subalgebra abeliana maximal contida na parte não-compacta de uma decomposição de Cartan de G. Tomamos então um semigrupo S Ì G com pontos interiores e descrevemos os conjuntos de controle para a ação de S nestas órbitas. Mostramos também que esses conjuntos não são comparáveis utilizando a relação de ordem usual para conjuntos de controle e descrevemos seus domínios de atração. Consideramos também o caso em que S é um semigrupo maximal, obtendo uma descrição melhor dos conjuntos de controle. Para compactificações de semigrupos, adotamos as mesmas hipóteses sobre G e tomamos S como o semigrupo de compressão de um subconjunto fechado da variedade ??ag?maximal de G. Obtemos uma compactificação do espaço homogêneo G/H, onde H denota o grupo das unidades de S, como um subconjunto dos conjuntos fechados de G e mostramos que quando G tem posto 1 é possível realizar a imagem de S/H por essa compactificações no conjunto dos subconjuntos fechados da variedade flag maximal de G / Abstract: In this work we study two distinct problems: semigroup actions on adjoint orbits and compactication of semigroups. For the study of the semigroup actions, we consider a semi-simple connected noncompact Lie group G and the adjoint orbit through elements in a maximal abelian subalgebra contained in the complement of a maximal compactly embedded subalgebra of the Lie algebra of G. We take then a semigroup S Ì G with interior points and describe the control sets for the S-action on these orbits. It is proved here that these control sets are no comparable and we describe its domains of attraction. We also consider the case in that S is a maximal semigroup and obtain a better description of the control sets. For the compactication of semigroups, we use the same hypothesis about G and consider S as the compression semigroup of a closed subset in the maximal ag manifold of G. We obtain a compactication of the homogeneous space G/H, where H=S ÇS-1, as a subset of the set of closed sets of G and we show that when G has rank one is possible to realize the image of S/H under this compacti?cation in the set of the closed subsets of the maximal ag manifold / Doutorado / Doutor em Matemática

Orientadores: Luiz Antonio Barrera San Martin, Paulo Regis Caron Ruffino / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica / Made available in DSpace on 2018-08-04T03:20:41Z (GMT). No. of bitstreams: 1 Lopez_JorgeNicolas_D.pdf: 956037 bytes, checksum: ce1c7712a7ab2ad21d0e46479e50f04a (MD5) Previous issue date: 2005 / Doutorado / Matematica / Doutor em Matemática

M.Sc. / In this dissertation, a symmetry analysis of a third order non-linear partial differential equation which describes the filtration of a non-Newtonian liquid in porous media is performed. A review of the derivation of the partial differential equation is given which is based on the Darcy Law. The partial differential equation contains a parameter n and a function f. We derive the Lie Point Symmetries of the partial differential equation for all cases of n and f. These symmetries are used to find the invariant solutions of the partial differential equation. We find that there is only one conservation law for the partial differential equation with f and n arbitrary and we prove that there is no potential symmetry corresponding to this conservation law for any case of n and f.

The purpose of our work is to study the physical aspects of the application of the Lie group analysis to simple harmonic oscillators and related systems which can or cannot be canonical ones. The mathematical part of the problem has been studied by many authors. Quite recently L. Hubbard, C.Wulfman and H. Rabitz and C. Wulfman and H.Rabitz have developed a method for a group theoretical analysis applicable to a more general class of linear systems of Ordinary Differential Equations (ODE).

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18767号 / 理博第4025号 / 新制||理||1580(附属図書館) / 31718 / 京都大学大学院理学研究科数学・数理解析専攻 / (主査)准教授 岸本 大祐, 教授 加藤 毅, 准教授 浅岡 正幸 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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Within the past decades, wavelets and associated wavelet transforms have been intensively investigated in both applied and pure mathematics. They and the related multi-scale analysis provide essential tools to describe, analyse and modify signals, images or, in rather abstract concepts, functions, function spaces and associated operators. We introduce the concept of diffusive wavelets where the dilation operator is provided by an evolution like process that comes from an approximate identity. The translation operator is naturally defined by a regular representation of the Lie group where we want to construct wavelets. For compact Lie groups the theory can be formulated in a very elegant way and also for homogeneous spaces of those groups we formulate the theory in the theory of non-commutative harmonic analysis. Explicit realisation are given for the Rotation group SO(3), the k-Torus, the Spin group and the n-sphere as homogeneous space. As non compact example we discuss diffusive wavelets on the Heisenberg group, where the construction succeeds thanks to existence of the Plancherel measure for this group. The last chapter is devoted to the Radon transform on SO(3), where the application on diffusive wavelets can be used for its inversion. The discussion of a variational spline approach provides criteria for the choice of points for measurements in concrete applications.

Si (π, H) est une représentation unitaire irréductible d'un groupe de Lie G, on sait lui associer son application moment Ψπ. La fermeture de l'image de Ψπ s'appelle l'ensemble moment de π. Généralement, cet ensemble est Conv(Oπ), si Oπ est l'orbite coadjointe associée à π. Mais il ne caractérise pas π : deux orbites distinctes peuvent avoir la même enveloppe convexe fermée. On peut contourner cette non séparation en considérant un surgroupe G+ de G et une application non linéaire ø de g* dans (g+)* telle que, pour les orbites générique, ø(O) est une orbite et Conv (ø(O)) caractérise O. Dans cette thèse, on montre que l'on peut choisir le couple (G+, ø), avec ø de degré ≤ 2 pour tous les groupes nilpotents de dimension ≤ 6, à une exception près, tous les groupes résolubles de dimension ≤ 4, et pour un exemple de groupe de déplacements. Ensuite, on étudie le cas des groupes G = SL(n, R). Pour ces groupes, il existe un tel couple avec ø de degré n, mais il n'en existe pas avec ø de degré 2 si n>2, il n'en existe pas avec ø de degré 3 si n=4. Enfin, on montre que l'application moment Ψπ est celle d'une action fortement hamiltonienne de G sur la variété de Fréchet symplectique PH∞. On construit un foncteur qui associe à tout G un surgroupe de Lie Fréchet G̃, de dimension infinie et, à tout π de G, une action π̃ fortement hamiltonienne, dont l'ensemble moment caractérise π / To a unitary irreducible representation (π,H) of a Lie group G, is associated a moment map Ψπ. The closure of the range of Ψπ is the moment set of π. Generally, this set is Conv(Oπ), if Oπ is the corresponding coadjoint orbit. Unfortunately, it does not characterize π : 2 distincts orbits can have the same closed convex hull. We can overpass this di culty, by considering an overgroup G+ for G and a non linear map ø from g* into (g+)* such that, for generic orbits, ø(O) is an orbit and Conv( ø(O)) characterizes O. In the present thesis, we show that we can choose the pair (G+,ø), with deg ø ≤2 for all the nilpotent groups with dimension ≤6, except one, for all solvable groups with diemnsion ≤4, and for an example of motion group. Then we study the G=SL(n,R) case. For these groups, there exists ø with deg ø =n, if n>2, there is no such ø with deg ø=2, if n=4, there is no such ø with deg ø=3. Finally, we show that the moment map Ψπ is coming from a stronly Hamiltonian G-action on the Frécht symplectic manifold PH∞. We build a functor, which associates to each G an infi nite diemnsional Fréchet-Lie overgroup G̃,and, to each π a strongly Hamiltonian action, whose moment set characterizes π

Within the past decades, wavelets and associated wavelet transforms have been intensively investigated in both applied and pure mathematics. They and the related multi-scale analysis provide essential tools to describe, analyse and modify signals, images or, in rather abstract concepts, functions, function spaces and associated operators. We introduce the concept of diffusive wavelets where the dilation operator is provided by an evolution like process that comes from an approximate identity. The translation operator is naturally defined by a regular representation of the Lie group where we want to construct wavelets. For compact Lie groups the theory can be formulated in a very elegant way and also for homogeneous spaces of those groups we formulate the theory in the theory of non-commutative harmonic analysis. Explicit realisation are given for the Rotation group SO(3), the k-Torus, the Spin group and the n-sphere as homogeneous space. As non compact example we discuss diffusive wavelets on the Heisenberg group, where the construction succeeds thanks to existence of the Plancherel measure for this group. The last chapter is devoted to the Radon transform on SO(3), where the application on diffusive wavelets can be used for its inversion. The discussion of a variational spline approach provides criteria for the choice of points for measurements in concrete applications.