Neste trabalho, estudamos famílias de curvas genericamente reduzidas. Estendemos para o caso genericamente reduzido alguns resultados conhecidos para famílias de curvas reduzidas como a equivalência entre a Whitney equisingularidade e a resolução simultânea forte da família e a equivalência entre a Whitney equisingularidade e a constância do número de Milnor e da multiplicidade de cada curva Xt da família. Estudamos também a equisingularidade topológica e a Whitney equisingularidade de famílias de superfícies em C3 parametrizadas por germes de aplicações A-finitamente determinados. Em ([51]), Ruas apresentou uma conjectura cujo enunciado diz que se f : (C2, 0) r→ (C3, 0) é um germe de aplicação finitamente determinado, então um desdobramento F a 1-parâmetro de f é topologicamente trivial se, e somente se F é Whitney equisingular se, e somente se o número de Milnor μ(D(ft)) de D(ft) é constante, onde D(ft) é a curva de pontos duplos de ft. Apresentamos contra-exemplos que mostram como esta conjectura pode falhar. Mostramos também uma classe de famílias de germes aplicações ft : (C2, 0) → (C3, 0) em que a conjectura é verdadeira. No caso em que f é homogênea e de coposto 1, mostramos também algumas fórmulas para a multiplicidade da imagem da curva de pontos duplos f(D(f)), o número de Milnor da seção transversal μ1(f(C2)) e o invariante J(f) em termos dos graus de f. Em [44], Nuño-Ballesteros e Jorge Pérez apresentam alguns resultados sobre germes de aplicações f : (Cn, 0) → (C2n-1, 0) com n ≥ 3. Quando f é finitamente determinado, a curva dos pontos duplos D(f) de f tem uma estrutura de curva genericamente reduzida. Apresentamos uma outra forma de abordar alguns problemas descritos em [44] usando resultados sobre curvas genericamente reduzidas. / In this work, we study families of generically reduced curves. We extend to the generically reduced case some results known for families of reduced curves as the equivalence between Whitney equisingularity and strong simultaneous resolution of the family and the equivalence between Whitney equisingularity and the constancy of the Milnor number and the multiplicity of each curve Xt of the family. We also study the topological triviality and the Whitney equisingularity of families of surfaces in C3 parametrized by A-finitely determined map germs. In [51], Ruas presented a conjecture whose statement says that if f : (C2, 0) → (C3, 0) is a finitely determined map germ, then an 1-parameter unfolding F = (ft, t) of f is topological trivial if and only if it is Whitney equisingular if and only if the Milnor number μ(D(ft)) is constant, where D(ft) is the double point curve of ft. We present counter-examples that show how the conjecture can fail. We also show a class of families of map germs ft : (C2, 0) → (C3, 0) in which the conjecture is true. We also give formulas for the multiplicity of the image of the double point curve f(D(f)), the Milnor number of the transversal generic section μ 1f(C2)) and the invariant J(f) in terms of degrees of f in the case in which f is homogeneous and has corank 1. In [44], Nuño-Ballesteros and Jorge Pérez give some results in the case of families of map germs f : (Cn, 0) → (C2n-1, 0) with n ≥ 3. When f is finitely determined, the double point. curve D(f) of f is a generically reduced curve. We present another way of approaching some problems in [44] using results on generically reduced curves.

This dissertation studies quantum invariants of knots and links, particularly the colored Jones polynomials, and their relationships with classical invariants like the hyperbolic volume and the A-polynomial. We consider the volume conjecture that relates the Kashaev invariant, a specialization of the colored Jones polynomial at a specific root of unity, and the hyperbolic volume of a link; and the AJ conjecture that relates the colored Jones polynomial and the A-polynomial of a knot. We establish the AJ conjecture for some big classes of two-bridge knots and pretzel knots, and confirm the volume conjecture for some cables of knots.

In this thesis, I have explored the different approaches towards proving Artin's `primitive root' conjecture unconditionally and the elliptic curve analogue of the same. This conjecture was posed by E. Artin in the year 1927, and it still remains an open problem. In 1967, C. Hooley proved the conjecture based on the assumption of the generalized Riemann hypothesis. Thereafter, the mathematicians tried to get rid of the assumption and it seemed quite a daunting task. In 1983, the pioneering attempt was made by R. Gupta and M. Ram Murty, who proved unconditionally that there exists a specific set of 13 distinct numbers such that for at least one of them, the conjecture is true. Along the same line, using sieve theory, D. R. Heath-Brown reduced this set down to 3 distinct primes in the year 1986. This is the best unconditional result we have so far. In the first part of this thesis, we will review the sieve theoretic approach taken by Gupta-Murty and Heath-Brown. The second half of the thesis will deal with the elliptic curve analogue of the Artin's conjecture, which is also known as the Lang-Trotter conjecture. Lang and Trotter proposed the elliptic curve analogue in 1977, including the higher rank version, and also proceeded to set up the mathematical formulation to prove the same. The analogue conjecture was proved by Gupta and Murty in the year 1986, assuming the generalized Riemann hypothesis, for curves with complex multiplication. They also proved the higher rank version of the same. We will discuss their proof in details, involving the sieve theoretic approach in the elliptic curve setup. Finally, I will conclude the thesis with a refinement proposed by Gupta and Murty to find out a finite set of points on the curve such that at least one satisfies the conjecture.

In this thesis, I have explored the different approaches towards proving Artin's `primitive root' conjecture unconditionally and the elliptic curve analogue of the same. This conjecture was posed by E. Artin in the year 1927, and it still remains an open problem. In 1967, C. Hooley proved the conjecture based on the assumption of the generalized Riemann hypothesis. Thereafter, the mathematicians tried to get rid of the assumption and it seemed quite a daunting task. In 1983, the pioneering attempt was made by R. Gupta and M. Ram Murty, who proved unconditionally that there exists a specific set of 13 distinct numbers such that for at least one of them, the conjecture is true. Along the same line, using sieve theory, D. R. Heath-Brown reduced this set down to 3 distinct primes in the year 1986. This is the best unconditional result we have so far. In the first part of this thesis, we will review the sieve theoretic approach taken by Gupta-Murty and Heath-Brown. The second half of the thesis will deal with the elliptic curve analogue of the Artin's conjecture, which is also known as the Lang-Trotter conjecture. Lang and Trotter proposed the elliptic curve analogue in 1977, including the higher rank version, and also proceeded to set up the mathematical formulation to prove the same. The analogue conjecture was proved by Gupta and Murty in the year 1986, assuming the generalized Riemann hypothesis, for curves with complex multiplication. They also proved the higher rank version of the same. We will discuss their proof in details, involving the sieve theoretic approach in the elliptic curve setup. Finally, I will conclude the thesis with a refinement proposed by Gupta and Murty to find out a finite set of points on the curve such that at least one satisfies the conjecture.

The thesis provides answers, in one case partial and in the other final, to two conjectures in the area of weighted inequalities for Singular Integral Operators. We study the mapping properties of these operators in weighted Lebesgue spaces with weight w. The novelty of this thesis resides in proving sharp dependence of the operator norm on the Muckenhoupt constant associated to the weigth w for a rich class of Singular Integral operators. The thesis also addresses the end point case p=1, providing counterexamples for the dyadic and continuous settings.

Neste trabalho, estudamos famílias de curvas genericamente reduzidas. Estendemos para o caso genericamente reduzido alguns resultados conhecidos para famílias de curvas reduzidas como a equivalência entre a Whitney equisingularidade e a resolução simultânea forte da família e a equivalência entre a Whitney equisingularidade e a constância do número de Milnor e da multiplicidade de cada curva Xt da família. Estudamos também a equisingularidade topológica e a Whitney equisingularidade de famílias de superfícies em C3 parametrizadas por germes de aplicações A-finitamente determinados. Em ([51]), Ruas apresentou uma conjectura cujo enunciado diz que se f : (C2, 0) r→ (C3, 0) é um germe de aplicação finitamente determinado, então um desdobramento F a 1-parâmetro de f é topologicamente trivial se, e somente se F é Whitney equisingular se, e somente se o número de Milnor μ(D(ft)) de D(ft) é constante, onde D(ft) é a curva de pontos duplos de ft. Apresentamos contra-exemplos que mostram como esta conjectura pode falhar. Mostramos também uma classe de famílias de germes aplicações ft : (C2, 0) → (C3, 0) em que a conjectura é verdadeira. No caso em que f é homogênea e de coposto 1, mostramos também algumas fórmulas para a multiplicidade da imagem da curva de pontos duplos f(D(f)), o número de Milnor da seção transversal μ1(f(C2)) e o invariante J(f) em termos dos graus de f. Em [44], Nuño-Ballesteros e Jorge Pérez apresentam alguns resultados sobre germes de aplicações f : (Cn, 0) → (C2n-1, 0) com n ≥ 3. Quando f é finitamente determinado, a curva dos pontos duplos D(f) de f tem uma estrutura de curva genericamente reduzida. Apresentamos uma outra forma de abordar alguns problemas descritos em [44] usando resultados sobre curvas genericamente reduzidas. / In this work, we study families of generically reduced curves. We extend to the generically reduced case some results known for families of reduced curves as the equivalence between Whitney equisingularity and strong simultaneous resolution of the family and the equivalence between Whitney equisingularity and the constancy of the Milnor number and the multiplicity of each curve Xt of the family. We also study the topological triviality and the Whitney equisingularity of families of surfaces in C3 parametrized by A-finitely determined map germs. In [51], Ruas presented a conjecture whose statement says that if f : (C2, 0) → (C3, 0) is a finitely determined map germ, then an 1-parameter unfolding F = (ft, t) of f is topological trivial if and only if it is Whitney equisingular if and only if the Milnor number μ(D(ft)) is constant, where D(ft) is the double point curve of ft. We present counter-examples that show how the conjecture can fail. We also show a class of families of map germs ft : (C2, 0) → (C3, 0) in which the conjecture is true. We also give formulas for the multiplicity of the image of the double point curve f(D(f)), the Milnor number of the transversal generic section μ 1f(C2)) and the invariant J(f) in terms of degrees of f in the case in which f is homogeneous and has corank 1. In [44], Nuño-Ballesteros and Jorge Pérez give some results in the case of families of map germs f : (Cn, 0) → (C2n-1, 0) with n ≥ 3. When f is finitely determined, the double point. curve D(f) of f is a generically reduced curve. We present another way of approaching some problems in [44] using results on generically reduced curves.

Dès qu’on manipule des ordres partiels (des hiérarchies), il est naturel de se demander comment les représenter dans un système informatique. Parmi les solutions proposées dans la littérature, on retrouve le codage par vecteur de bits. Dans cette thèse, nous nous intéressons au problème de calcul d’un codage des ordres par vecteur de bits de taille minimale, aussi connu par le problème de calcul de la 2-dimension des ordres, qui est NP-complet. Nous proposons des solutions du problème de nature heuristique, pour le cas général et pour des classes d’ordres particulières.Cette thèse présente également des résultats sur des conjectures autour de la 2-dimension des arbres. Notamment celle de Habib et al. à propos de la 2-approximabilité de la 2-dimension des arbres. Nous proposons quelques pistes de preuve de cette conjecture puis une reformulation, permettant d’apporter un nouveau regard sur le problème en question et d’espérer trouver des codages des ordres par vecteur de bits efficaces et de taille inférieure à leur 2-dimension. Nous apportons une réponse négative à deux autres conjectures. / The main question asked when manipulating partial orders (hierarchies), is how to represent them in computer. Among solutions proposed in literature, there is the bit-vector encoding. In this thesis, we consider the problem of computing a bit-vector encoding of orders with minimal size, which is also known as the problem of computing the2-dimension of orders that is NP-complete. We propose heuristics solutions of the problem for the general case and for some particular order classes. In addition, this thesis presents some results about conjectures on the 2-dimension of trees. Especially, the conjecture of Habib et al. about the 2-approximability of the 2-dimension of trees. We propose some ideas of a proof of this conjecture then give a reformulation of it that brings new perspectives on the problem that are finding efficient bits-vector encodings of orders of size less than their 2-dimension. We disprove two other conjectures.

La complexité arithmétique est l’étude des ressources nécessaires pour calcu- ler des polynômes en n’utilisant que des opérations arithmétiques. À la fin des années 70, Valiant a défini (de manière semblable à la complexité booléenne) des classes de polynômes. Les polynômes, ayant des circuits de taille polyno- miale, considérés faciles forment la classe VP. Les sommes exponentielles de ces derniers correpondent alors à la classe VNP. L’hypothèse de Valiant est la conjecture que VP ̸= VNP.Bien que cette conjecture soit encore grandement ouverture, cette dernière semble toutefois plus accessible que son homologue booléen. La structure algé- brique sous-jacente limite les possibilités de calculs. En particulier, un résultat important du domaine assure que les polynômes faciles peuvent aussi être cal- culés efficacement en paralèlle. De plus, quitte à autoriser une augmentation raisonnable de la taille, il est possible de les calculer avec une profondeur de calcul bornée par une constante. Comme ce dernier modèle est très restreint, de nombreuses bornes inférieures sont connues. Nous nous intéresserons en premier temps à ces résultats sur les circuits de profondeur constante.Bürgisser a montré qu’une conjecture (la τ-conjecture) qui borne supérieu- rement le nombre de racines de certains polynômes univariés, impliquait des bornes inférieures en complexité arithmétique. Mais, que se passe-t-il alors, si on essaye de réduire, comme précédemment, la profondeur du polynôme consi- déré? Borner le nombre de racines réelles de certaines familles de polynômes permetterait de séparer VP et VNP. Nous étudierons finalement ces bornes su- périeures sur le nombre de racines réelles. / Arithmetic complexity is the study of the required ressources for computing poynomials using only arithmetic operations. In the last of the 70s, Valiant defined (similarly to the boolean complexity) some classes of polynomials. The polynomials which have polynomial size circuits form the class VP. Exponential sums of these polynomials correspond to the class VNP. Valiant’s hypothesis is the conjecture that VP is different tVNP.Although this conjecture is still open, it seems more accessible than its boolean counterpart. The induced algebraic structure limits the possibilities of the computation. In particular, an important result states that the low de- gree polynomials can be efficiently computed in parallel. Moreover, if we allow a fair increasement of the size, it is possible to compute them with a constant depth. As this last model is very particular, some lower bounds are known.Bürgisser showed that a conjecture (τ-conjecture) which bounds the number of roots of some univariate polynomials, implies lower bounds in arithmetic complexity. But, what happens if we try to reduce as before the depth of the circuits for the polynomials? Bounding the number of real roots of some families of polynomials would imply a separation between VP and VNP. Finally we willstudy these upper bounds on the number of real roots.

Na presente dissertação, discutimos o Problema do Isomorfismo em anéis de grupo para grupos infinitos da forma G × C, apresentado no artigo de Mazur [14], que enuncia um teorema mostrando a equivalência para o Problema do Isomorfismo entre essa classe de grupos infinitos e grupos finitos que satisfaçam a Conjectura do Normalizador. Nossa ênfase concentra-se na relação entre a Conjectura do Isomorfismo e a Conjectura do Normalizador, primeiramente, observada nesse artigo. Em seguida, consideramos um teorema de estrutura para as unidades centrais em anéis de grupo comunicado, pela primeira vez, no artigo de Jespers-Parmenter-Sehgal [9], e generalizado por Polcino Milies-Sehgal em [17], e Jespers-Juriaans em [7]. Evidenciamos a importância desse teorema para a Teoria de Anéis de Grupo e apresentamos uma nova demonstração para o teorema de equivalência de Mazur, considerando, para tanto, uma apropriada unidade central e sua estrutura, caracterizada pelo teorema comunicado para as unidades centrais. Concluímos a dissertação, descrevendo a construção do grupo das unidades centrais para o anel de grupo ZA5 , um grupo livre finitamente gerado de posto 1, utilizando a construção dada no artigo de Aleev [1]. / In this dissertation, we discuss the Problem of the Isomorphism in group rings for infinite groups as G × C. This is presented in [14]. Such article states a theorem which shows an equivalence to the isomorphism problem between that infinite class group and finite groups verifying the Normalizer Conjecture. Our main purpose is the Normalizer Conjecture and the Isomorphism Conjecture relationship remarked in the cited article to the groups above. Following, we consider a group ring theorem to the central units subgroup firstly communicated in [9] and generalized in [17] and [7]. We point up the importance of such theorem to the Group Ring Theory and we give a short and a new demonstration to Mazurs equivalence theorem from using a suitable central unit altogether with its structure lightly by the Central Unit Theorem on focus. We conclude this work sketching the ZA5 central units subgroup on showing it is a free finitely generated group of rank 1 from the presenting construction in Aleevs article [1].

Cette thèse est centrée autour de la monogénéité de corps de nombres en situation relative puis à la conjecture de Collatz.\newline Premièrement on détermine l'ensemble de classes des générateurs de l'anneau des entiers des certaines extensions relatives de corps de nombres, en utilisant l'algorithme de Gaál & Phost et le logiciel PARI/GP. La deuxième partie propose différents formulations d'une généralisation de la conjecture de Collatz, aux entiers p-adiques. On étudie ensuite le comportement de suites analogues dans le cadre d'anneaux d'entiers de corps de nombres. / This thesis are centered around the monogeneity of number fields in a relative situation and the Collatz conjecture. Firstly, we determine the set of generator classes of the ring of integers of some relative extensions of number fields, using the Gaál& Phost algorithm and the PARI/GP software. The second part proposes different formulations of a generalization of the Collatz conjecture to p-adic integers. We then study the behavior of similar sequences in the framework of rings of integers of number fields.