Des travaux de didactique des mathématiques, conduits par Briand, ont permis de montrer l’existence de connaissances spécifiques d’organisation dans le domaine des problèmes concernant le dénombrement et les opérations arithmétiques, connaissances qui relèvent de ce que Brousseau a appelé l’énumération. Cette thèse montre que ces « connaissances d’énumération » ne sont spécifiques ni au champ numérique, ni même aux mathématiques. Elles se retrouvent dans de nombreuses situations scolaires et présentent un caractère transdisciplinaire. L’étude de la situation fondamentale de l’énumération permet d’exhiber de nouvelles variables et de compléter l’étude des stratégies. Une nouvelle définition de l’énumération est proposée, permettant d’unifier la description des difficultés rencontrées. Le caractère transdisciplinaire de l’énumération est étudié dans le domaine scolaire « français ». Les situations étudiées dans ce cadre permettent d’intégrer la dimension de l’écrit dans la description de ces connaissances. Du point de vue méthodologique, des analyses a priori successives montrent comment les modifications de point de vue permettent de faire évoluer le modèle, proposant notamment une nouvelle modélisation du traitement / Research work on mathematics education, carried out by Briand, have shown the existence of specific knowledge in the field of numerical problems, involving counting or arithmetic operations, which reveal what Brousseau has named “enumeration”. This thesis shows that enumeration’s knowledge are not specific to the numerical field, neither to mathematics. This knowledge can be founded in many scholar situation and show an interdisciplinary character. The study of the fundamental situation is down, which allows to unify the description of the subject’s difficulties. The interdisciplinary character is studied in the scholar field of language. The study of these situations in this context allows us to incorporate the dimension of writing in our descriptions of the knowledge. Considering metrology, theses analyses show how modifications of point of view enable an evolution of the model, allowing in particular of new modeling of treatment.

Factor mixture modeling (FMM) has been increasingly used to investigate unobserved population heterogeneity. This Monte Carlo simulation study examined the issue of measurement invariance testing with FMM when there are covariate effects. Specifically, this study investigated the impact of excluding and misspecifying covariate effects on the class enumeration and measurement invariance testing with FMM. Data were generated based on three FMM models where the covariate had impact on the latent class membership only (population model 1), both the latent class membership and the factor (population model 2), and the latent class membership, the factor, and one item (population model 3). The number of latent classes was fixed at two. These two latent classes were distinguished by factor mean difference for conditions where measurement invariance held in the population, and by both factor mean difference and intercept differences across classes when measurement invariance did not hold in the population. For each of the population models, different analysis models that excluded or misspecified covariate effects were fitted to data. Analyses consisted of two parts. First, for each analysis model, class enumeration rates were examined by comparing the fit of seven solutions: 1-class, 2-class configural, metric, and scalar, and 3-class configural, metric, and scalar. Second, assuming the correct solution was selected, the fit of analysis models with the same solution was compared to identify a best-fitting model. Results showed that completely excluding the covariate from the model (i.e., the unconditional model) would lead to under-extraction of latent classes, except when the class separation was large. Therefore, it is recommended to include covariate in FMM when the focus is to identify the number of latent classes and the level of invariance. Specifically, the covariate effect on the latent class membership can be included if there is no priori hypothesis regarding whether measurement invariance might hold or not. Then fit of this model can be compared with other models that included covariate effects in different ways but with the same number of latent classes and the same level of invariance to identify a best-fitting model.

The process of coset enumeration has become a significant factor in group theoretical investigations since the advent of modern computing power, but in some respects the process is still not well understood. This thesis investigates some features of coset enumeration, working mainly with the group F(2,7). Chapter 1 describes the characteristics of coset enumeration and algorithms used for it. A worked example of the method is provided. Chapter 2 discusses some features which would be desirable in computer programs for use in investigating the coset enumeration process itself, and reviews the Havas/Alford program which to date best meets the requirements. Chapter 3 deals with the use of coset ammeration in proofs, either in its own right or as a basis for other workings. An example of one attempt to obtain a proof by coset enumeration is given. Chapter 4 reviews techniques designed to reduce the length of coset enumerations and proposes the 'equality list' technique as a way to reduce enumeration length for some groups. Extra insights obtainable using the equality list method are also discussed. Chapter 5 summarises the factors by which the success of different coset enumerations can be compared and proposes an algorithm for making systematic comparisons among enumerations. Chapter 6 reports five coset enumerations, obtained manually by three main methods on the group F(2,7). All these enumerations were shorter than is so far obtainable by machine and one is shorter than other known hand enumerations. The enumerations were compared by applying the process developed in Chapter 5. Chapter 7 presents a shorter proof of the cyclicity of the group F(2,7) than was hitherto available. The proof derives from the workings for one of the coset enumerations described in Chapter 6. There are eight appendices and an annotated bibliography. The appendices contain, inter alia, edited correspondence between well-known coset-enumerators, a guide to the Havas/Alford program, further details on the equality list method and listings of various enumerations.

<p>In this thesis a method for solving the Generalized Assignment Problem (GAP) is described. It is based on a reformulation of the original problem into a Set Partitioning Problem (SPP), in which the columns represent partial solutions to the original problem. For solving this problem, column generation, with systematic overgeneration of columns, is used. Conditions that guarantee that an optimal solution to a restricted SPP is optimal also in the original problem are given. In order to satisfy these conditions, not only columns with the most negative Lagrangian reduced costs need to be generated, but also others; this observation leads to the use of overgeneration of columns.</p><p>The Generalized Assignment Problem has shown to be NP-hard and therefore efficient algorithms are needed, especially for large problems. The application of the proposed method decomposes GAP into several knapsack problems via Lagrangian relaxation, and enumerates solutions to each of these problems. The solutions obtained from the knapsack problems form a Set Partitioning Problem, which consists of combining one solution from each knapsack problem to obtain a solution to the original problem. The algorithm has been tested on problems with 10 agents and 60 jobs. This leads to 10 knapsack problems, each with 60 variables.</p>

In this thesis a method for solving the Generalized Assignment Problem (GAP) is described. It is based on a reformulation of the original problem into a Set Partitioning Problem (SPP), in which the columns represent partial solutions to the original problem. For solving this problem, column generation, with systematic overgeneration of columns, is used. Conditions that guarantee that an optimal solution to a restricted SPP is optimal also in the original problem are given. In order to satisfy these conditions, not only columns with the most negative Lagrangian reduced costs need to be generated, but also others; this observation leads to the use of overgeneration of columns. The Generalized Assignment Problem has shown to be NP-hard and therefore efficient algorithms are needed, especially for large problems. The application of the proposed method decomposes GAP into several knapsack problems via Lagrangian relaxation, and enumerates solutions to each of these problems. The solutions obtained from the knapsack problems form a Set Partitioning Problem, which consists of combining one solution from each knapsack problem to obtain a solution to the original problem. The algorithm has been tested on problems with 10 agents and 60 jobs. This leads to 10 knapsack problems, each with 60 variables.

The problem of counting ramified covers of a Riemann surface up to homeomorphism was proposed by Hurwitz in the late 1800's. This problem translates combinatorially into factoring a permutation with a specified cycle type, with certain conditions on the cycle types of the factors, such as minimality and transitivity. Goulden and Jackson have given a proof for the number of minimal, transitive factorizations of a permutation into transpositions. This proof involves a partial differential equation for the generating series, called the Join-Cut equation. Furthermore, this argument is generalized to surfaces of higher genus. Recently, Bousquet-M&eacute;lou and Schaeffer have found the number of minimal, transitive factorizations of a permutation into arbitrary unspecified factors. This was proved by a purely combinatorial argument, based on a direct bijection between factorizations and certain objects called <em>m</em>-Eulerian trees. In this thesis, we will give a new proof of the result by Bousquet-M&eacute;lou and Schaeffer, introducing a simple partial differential equation. We apply algebraic methods based on Lagrange's theorem, and combinatorial methods based on a new use of Bousquet-M&eacute;lou and Schaeffer's <em>m</em>-Eulerian trees. Some partial results are also given for a refinement of this problem, in which the number of cycles in each factor is specified. This involves Lagrange's theorem in many variables.

The problem of counting ramified covers of a Riemann surface up to homeomorphism was proposed by Hurwitz in the late 1800's. This problem translates combinatorially into factoring a permutation with a specified cycle type, with certain conditions on the cycle types of the factors, such as minimality and transitivity. Goulden and Jackson have given a proof for the number of minimal, transitive factorizations of a permutation into transpositions. This proof involves a partial differential equation for the generating series, called the Join-Cut equation. Furthermore, this argument is generalized to surfaces of higher genus. Recently, Bousquet-M&eacute;lou and Schaeffer have found the number of minimal, transitive factorizations of a permutation into arbitrary unspecified factors. This was proved by a purely combinatorial argument, based on a direct bijection between factorizations and certain objects called <em>m</em>-Eulerian trees. In this thesis, we will give a new proof of the result by Bousquet-M&eacute;lou and Schaeffer, introducing a simple partial differential equation. We apply algebraic methods based on Lagrange's theorem, and combinatorial methods based on a new use of Bousquet-M&eacute;lou and Schaeffer's <em>m</em>-Eulerian trees. Some partial results are also given for a refinement of this problem, in which the number of cycles in each factor is specified. This involves Lagrange's theorem in many variables.

The character theory of the symmetric group is a powerful method of studying enu- merative questions about factorizations of permutations, which arise in areas including topology, geometry, and mathematical physics. This method relies on having an encoding of the enumerative problem in the centre Z(n) of the algebra C[S_n] spanned by the symmetric group S_n. This thesis develops methods to deal with permutation factorization problems which cannot be encoded in Z(n). The (p,q,n)-dipole problem, which arises in the study of connections between string theory and Yang-Mills theory, is the chief problem motivating this research. This thesis introduces a refinement of the (p,q,n)-dipole problem, namely, the (a,b,c,d)- dipole problem. A Join-Cut analysis of the (a,b,c,d)-dipole problem leads to two partial differential equations which determine the generating series for the problem. The first equation determines the series for (a,b,0,0)-dipoles, which is the initial condition for the second equation, which gives the series for (a,b,c,d)-dipoles. An analysis of these equa- tions leads to a process, recursive in genus, for solving the (a,b,c,d)-dipole problem for a surface of genus g. These solutions are expressed in terms of a natural family of functions which are well-understood as sums indexed by compositions of a binary string. The combinatorial analysis of the (a,b,0,0)-dipole problem reveals an unexpected fact about a special case of the (p,q,n)-dipole problem. When q=n−1, the problem may be encoded in the centralizer Z_1(n) of C[S_n] with respect to the subgroup S_{n−1}. The algebra Z_1(n) has many combinatorially important similarities to Z(n) which may be used to find an explicit expression for the genus polynomials for the (p,n−1,n)-dipole problem for all values of p and n, giving a solution to this case for all orientable surfaces. Moreover, the algebraic techniques developed to solve this problem provide an alge- braic approach to solving a class of non-central problems which includes problems such as the non-transitive star factorization problem and the problem of enumerating Z_1- decompositions of a full cycle, and raise intriguing questions about the combinatorial significance of centralizers with respect to subgroups other than S_{n−1}.

The character theory of the symmetric group is a powerful method of studying enu- merative questions about factorizations of permutations, which arise in areas including topology, geometry, and mathematical physics. This method relies on having an encoding of the enumerative problem in the centre Z(n) of the algebra C[S_n] spanned by the symmetric group S_n. This thesis develops methods to deal with permutation factorization problems which cannot be encoded in Z(n). The (p,q,n)-dipole problem, which arises in the study of connections between string theory and Yang-Mills theory, is the chief problem motivating this research. This thesis introduces a refinement of the (p,q,n)-dipole problem, namely, the (a,b,c,d)- dipole problem. A Join-Cut analysis of the (a,b,c,d)-dipole problem leads to two partial differential equations which determine the generating series for the problem. The first equation determines the series for (a,b,0,0)-dipoles, which is the initial condition for the second equation, which gives the series for (a,b,c,d)-dipoles. An analysis of these equa- tions leads to a process, recursive in genus, for solving the (a,b,c,d)-dipole problem for a surface of genus g. These solutions are expressed in terms of a natural family of functions which are well-understood as sums indexed by compositions of a binary string. The combinatorial analysis of the (a,b,0,0)-dipole problem reveals an unexpected fact about a special case of the (p,q,n)-dipole problem. When q=n−1, the problem may be encoded in the centralizer Z_1(n) of C[S_n] with respect to the subgroup S_{n−1}. The algebra Z_1(n) has many combinatorially important similarities to Z(n) which may be used to find an explicit expression for the genus polynomials for the (p,n−1,n)-dipole problem for all values of p and n, giving a solution to this case for all orientable surfaces. Moreover, the algebraic techniques developed to solve this problem provide an alge- braic approach to solving a class of non-central problems which includes problems such as the non-transitive star factorization problem and the problem of enumerating Z_1- decompositions of a full cycle, and raise intriguing questions about the combinatorial significance of centralizers with respect to subgroups other than S_{n−1}.

This thesis contains several results concerning the combinatorics of partially ordered sets (posets) which are either of enumerative or extremal nature. <br><br> The first concerns conjectures of Friedland and Kahn, which state that the (extremal) d-regular graph on N vertices containing both the maximal number of matchings and independent sets of a fixed size is the graph consisting of disjoint union of appropriate number of complete bipartite d-regular graphs on 2d vertices. We show that the conjectures are true in an asymptotic sense, using entropy techniques. <br><br> As a second result, we give tight bounds on the size of the largest Boolean family which contains no three distinct subsets forming an "induced V" (i.e. if A,B,C are all in our family, if C is contained in the intersection of A B, A must be a subset of B). This result, though similar to known results, gives the first bound on a family defined by an induced property. <br><br> We pose both Dedekind-type questions concerning the number of antichains and a Stanley-type question concerning the number of linear extensions in generalized Boolean lattices; namely, products of chain posets and the poset of partially defined functions. We provide asymptotically tight bounds for these problems. <br><br> A Boolean function, f, is called cherry-free if for all triples x,y,z where z covers both x and y, f(z)=1 whenever both f(x)=1 and f(y)=1. We give bounds on the number of cherry-free functions on bipartite regular posets, with stronger results for bipartite posets under an additional co-degree hypotheses. We discuss applications of these functions to Boolean Horn functions and similar structures in ranked regular posets.