Thèse de doctorat Discipline: Mathématiques

This thesis is concerned with the development and application of categorical tools in the study of the cluster algebras of S. Fomin and A. Zelevinsky. C. Amiot’s generalized cluster category is a triangulated category which has been used, in the case where it is Hom-finite, to categorify a certain class of cluster algebras, using cluster characters in the sense of Y. Palu. In this thesis, we generalize these results to the case where the cluster category is not Hom-finite, thus obtaining a categorification of any skew-symmetric cluster algebra. In order to do so, we restrict ourselves to a subcategory of the cluster category which is stable under mutation and satisfies an analogue of the 2-Calabi–Yau condition. We prove the existence of a cluster character on this subcategory. We then use these tools to interpret the combinatorics of cluster algebras inside the cluster category. In particular, we prove a correspondence between g-vectors and indices, provide an interpretation of F polynomials, and show that the definition of mutation in the algebra and in the category are consistent with each other. These properties allow us to give new proofs of numerous conjectures for skew-symmetric cluster algebras. Finally, starting from recent work by C. Geiss, B. Leclerc and J. Schröer, we show how the set of indices parametrizes a basis for a class of cluster algebras. We then show that this construction provides us with a good candidate for a basis of the upper cluster algebra in general.