Factorisation of the product of Dirichlet series of completely multiplicative functions

Abstract

In the first chapter, we will present a computation of the square value of the module of L functions associated to a Dirichlet character. This computation suggests to ask if a certain ring of arithmetic multiplicative functions exists and if it is unique. This search has led to the construction of that ring in chapter two. Finally, in the third chapter, we will present some propositions associated with this ring. The result below is one of the main results of this work : For F and G two completely multiplicative functions, $ s $ a complex number such as the dirichlet series $ D(F,s) $ and $ D(G,s) $ converge : $ \forall F,G \in \mathbb{M}_{c} : D(F,s) \times D(G,s) = D(F \times G,2s) \times D(F \square G,s) $ where the operation $ \square $ is defined in chapter two as the sum of the previously mentioned ring. Here are some similar versions, with $ s = x+iy $ : $ \forall F, G \in \mathbb{M}_{c} : ~ D(F,s) \times D(G,\overline{s}) = D(F \times G,2x) \times D(\frac{F}{\text{Id}_{e}^{iy}} \square \frac{G}{\text{Id}_{e}^{-iy}}, x) $ $ \forall F, G \in \mathbb{M}_{c} : ~ |D(F,s)|^{2} = D(|F|^{2},2x) \times D(\frac{F}{\text{Id}_{e}^{iy}} \square \overline{\frac{F}{\text{Id}_{e}^{iy}}}, x) $