CategoriesIn this chapter we review some basics of category theory and representation theory. We will extend the representation theory of algebras to categories and discuss Morita equivalence in this context. Most of the material covered can be found in every standard book about category theory or representation theory [176, 148, 258]. We include it to fix notation and as a reference because in later chapters we will expand this formalism to the world of A ∞ -categories.
CategoriesDefinition 1.1 A category C consists of a collection of objects Ob(C) and for each pair of objects A, B ∈ Ob(C) there is a set C(A, B). This set is the homspace from A to B and its elements are called morphisms. They satisfy the following properties: