Le premier chapitre montre par des méthodes toriques ($G-$graphes) que pour tout entier positif $n$, le quotient de l'espace affine à $n$ dimensions par le groupe cyclique $G_n$ d'ordre $2^n-1$ admet le $G_n$-schema de Hilbert comme résolution lisse crepante. Le deuxième chapitre contient des résultats sur les champs algébriques (construction du champ algébrique lisse associé à une log-paire). Le troisième chapitre montre l'équivalence entre la catégorie dérivée bornée des faisceaux cohérents $G_n-$équivariants sur l'espace affine et celle des faisceaux cohérents sur la résolution $G_n-$Hilb. Chapitre 4 donne une réalisation géométrique de la conjecture de Broué via la correspondance de McKay. L'annexe contient des résultats sur les groupes trihédraux, y compris un programme magma.

We study projective completions of affine algebraic varieties (defined over an algebraically closed field K) which are given by filtrations, or equivalently, integer valued `degree like functions' on their rings of regular functions. For a polynomial map P := (P_1, ..., P_n): X -> K^n of affine varieties with generically finite fibers, we prove that there are completions of the source such that the intersection of completions of the hypersurfaces {P_j = a_j} for generic (a_1, ..., a_n) in K^n coincides with the respective fiber (in short, the completions `do not add points at infinity' for P). Moreover, we show that there are `finite type' completions with the latter property, i.e. determined by the maximum of a finite number of `semidegrees', by which we mean degree like functions that send products into sums. We characterize the latter type completions as the ones for which ideal I of the `hypersurface at infinity' is radical. Moreover, we establish a one-to-one correspondence between the collection of minimal associated primes of I and the unique minimal collection of semidegrees needed to define the corresponding degree like function. We also prove an `affine Bezout type' theorem for polynomial maps P with finite fibers that admit semidegrees corresponding to completions that do not add points at infinity for P. For a wide class of semidegrees of a `constructive nature' our Bezout-type bound is explicit and sharp.

We study projective completions of affine algebraic varieties (defined over an algebraically closed field K) which are given by filtrations, or equivalently, integer valued `degree like functions' on their rings of regular functions. For a polynomial map P := (P_1, ..., P_n): X -> K^n of affine varieties with generically finite fibers, we prove that there are completions of the source such that the intersection of completions of the hypersurfaces {P_j = a_j} for generic (a_1, ..., a_n) in K^n coincides with the respective fiber (in short, the completions `do not add points at infinity' for P). Moreover, we show that there are `finite type' completions with the latter property, i.e. determined by the maximum of a finite number of `semidegrees', by which we mean degree like functions that send products into sums. We characterize the latter type completions as the ones for which ideal I of the `hypersurface at infinity' is radical. Moreover, we establish a one-to-one correspondence between the collection of minimal associated primes of I and the unique minimal collection of semidegrees needed to define the corresponding degree like function. We also prove an `affine Bezout type' theorem for polynomial maps P with finite fibers that admit semidegrees corresponding to completions that do not add points at infinity for P. For a wide class of semidegrees of a `constructive nature' our Bezout-type bound is explicit and sharp.

We describe combinatorial techniques for studying log Calabi-Yau surfaces. These can be viewed as generalizing the techniques for studying toric varieties in terms of their character and cocharacter lattices. These lattices are replaced by certain integral linear manifolds described in [GHK11], and monomials on toric varieties are replaced with the canonical theta functions defined in [GHK11] using ideas from mirror symmetry. We classify deformation classes of log Calabi-Yau surfaces in terms of the geometry of these integral linear manifolds. We then describe the tropicalizations of theta functions and use them to generalize the dual pairing between the character and cocharacter lattices. We use this to describe generalizations of dual cones, Newton and polar polytopes, Minkowski sums, and finite Fourier series expansions. We hope that these techniques will generalize to higher rank cluster varieties. / text

We introduce a new type of sparse CSS quantum error correcting code based on the homology of hypermaps. Sparse quantum error correcting codes are of interest in the building of quantum computers due to their ease of implementation and the possibility of developing fast decoders for them. Codes based on the homology of embeddings of graphs, such as Kitaev's toric code, have been discussed widely in the literature and our class of codes generalize these. We use embedded hypergraphs, which are a generalization of graphs that can have edges connected to more than two vertices. We develop theorems and examples of our hypermap-homology codes, especially in the case that we choose a special type of basis in our homology chain complex. In particular, the most straightforward generalization of the m × m toric code to hypermap-homology codes gives us a [(3/2)m²,2, m] code as compared to the toric code which is a [2m²,2, m]code. Thus we can protect the same amount of quantum information, with the same error-correcting capability, using less physical qubits.

This dissertation demonstrates a procedure to view any quasitoric manifold as a “minimal” sub-manifold of an ambient quasitoric manifold of codimension two via the wedge construction applied to the quotient polytope. These we term wedge quasitoric manifolds. We prove existence utilizing a construction on the quotient polytope and characteristic matrix and demonstrate conditions allowing the base manifold to be viewed as dual to the first Chern class of the wedge manifold. Such dualization allows calculations of KO characteristic classes as in the work of Ochanine and Fast. We also examine the Todd genus as it relates to two types of wedge quasitoric manifolds. Background matter on polytopes and toric topology, as well as spin and complex cobordism are provided.

這篇論文裡，我們研究熱帶環面曲體，尤其是熱帶環面法諾曲體。如同古典代數幾何裡的情況一樣，要建構熱帶環面曲體，我們先從扇型開始建構。然而在某些結構裡沒辦法有熱帶化的對應，因此我們需要選一個適當的定義，這個定義必需可看成是古典情況類推而來的。在我們的論文中，使用我們認為合適的定義，計算所有平滑二維熱帶環面法諾曲體的情況，結果也證實非常類似古典的情形。 / In this thesis, we survey and study tropical toric varieties with focus on tropical toric Fano varieties. To construct tropical toric varieties, we start with fans, just like the situation in classical algebraic geometry. However, some constructions does not make sense in tropical settings. Therefore, we need to choose a reasonable definition which give an analogue of a classical toric variety. In the end of this paper, we use the definition we choose, and explicitly calculate all smooth two-dimensional tropical toric Fano varieties which we found are very similar to classical cases.

Depuis les 50 dernières années, de nombreux progrès ont été faits dans la compréhension du comportement asymptotique du nombre de points rationnels de hauteur bornée sur les variétés algébriques. Des conjectures précises ont été avancées par Baryrev, Manin et Peyre quant à la formule asymptotique attendue pour une variété générale.En 1962, à l'aide d'arguments issus de la méthode du cercle de Hardy et Littlewood, B. Birch a donné une estimation précise du nombre de points à coordonnées entières bornées dans une hypersurface définie par une équation homogène. Ceci revient à démontrer la conjecture de Batyrev-Manin-Peyre pour les hypersurfaces de l'espace projectif. Plus récemment, V. Blomer et J. Brüdern ont élaboré des techniques leur permettant d'établir une formule pour le comportement asymptotique du nombre de points de hauteur bornée pour des hypersurfaces d'espaces multiprojectifs définies par des équations multihomogènes diagonales. Parallèlement, D. Schindler a démontré la conjecture pour des hypersurfaces générales d'espaces biprojectifs, à l'aide de développements de la méthode de Birch.L'objet de cette thèse a été d'utiliser et de généraliser les techniques de Schindler, Blomer et Brüdern afin de démontrer la validité de la conjecture de Batyrev-Manin-Peyre pour le cas d'hypersurfaces de variétés toriques plus générales.Ce travail est composé de trois parties. La première partie concerne le cas particulier des hypersurfaces de tridegré (1,1,1) d'un espace triprojectif. Ce cas particulier constitue une première extension des techniques de Schindler à des variétés toriques dont le rang du groupe de Picard est 3. La deuxième partie est consacrée à l'étude des hypersurfaces d'une famille de variétés toriques dont le rang du groupe de Picard est 2 et contenant la famille des espaces biprojectifs. Il s'agit en effet d'étendre la méthode de Schindler afin d'obtenir une formule asymptotique pour le nombre de points de hauteur bornée sur ces variétés. Enfin, dans la dernière partie, nous généralisons les méthodes développées dans les deux parties précédentes à des hypersurfaces des variétés toriques complètes lisses de rang de groupe dont le cône effectif est supposé simplicial, ce qui nous permet de démontrer la conjecture de Batyrev-Manin-Peyre pour ces variétés. / For the last 50 years, many progresses have been made in the understanding of the asymptotic behaviour of the number of rational points of bouded height on algebraic varieties. Some precise conjectures have been advanced by Batyrev, Manin, and Peyre for the expected asymptotic formula for a general variety.In 1962, using some arguments of the Hardy-Littlewood circle method, B. Birch gave a precise estimate for the number of integral points whose coordinates are bounded on an hypersurface defined by an homogeneous equation. This amounts to demonstrating the Batyrev-Manin-Peyre conjecture for hypersurfaces of projective spaces. More recently, V. Blomer and J. Brüdern developed some methods permitting to establish a formula for the asymptotic growth of the number of points of bounded height on hypersurfaces of multiprojective spaces defined by multihomogeneous diagonal equations. In the same time, D. Schindler proved the conjecture for general hypersurfaces of biprojective spaces by using some developements of the method of Birch.The aim of this thesis was to use and generalize the methods of Schindler, blomer, and Brüdern in order to prove the Batyrev-Manin-Peyre conjecture in the case of hypersurfaces of some general toric varieties.This work contain three parts. The first one deals with the particular case of hypersurfaces of tridegree (1,1,1) of triprojective spaces. This particular case is a first extension of the method of Schindler to some toric varieties whose rank of the Picard group is 3. The second part deals with the study of hypersurfaces of a class of toric varieties whose rank of the Picard group is 2 and containing biprojective spaces. We establish a generalization of the method of Schindler method in order to find an asymptotic formula for the number of points of bounded height on these vrieties. Finally, in the last part, we generalize the methods developed in the last two part to treat the case of hypersurfaces of complete non-singular toric vareties whose effective cone is simplicial. This permits to prove the conjecture of batyrev-Manin-Peyre for these varieties.

No description available.

Toric face rings are a generalization of Stanley-Reisner rings and affine monoid rings. New problems and results are obtained by a systematic study of toric face rings, shedding new lights to the understanding of Stanley-Reisner rings and affine monoid rings. We study algebra retracts of Stanley-Reisner rings, in particular, classify all the $\mathbb{Z}$-graded algebra retracts. We consider the Koszul property of toric face rings via Betti numbers and properties of the defining ideal. The last chapter is devoted to local cohomology of seminormal toric face rings and applications to singularities of toric face rings in positive characteristics.