Eulerian idempotent and Kashiwara-Vergne conjecture
By using the interplay between the Eulerian idempotent and the Dynkin idempotent, we construct explicitly a particular symmetric solution of the first equation of the Kashiwara-Vergne conjecture Then, we explicit all the solutions of the equation in the completion of the free Lie algebra generated by two indeterminates and thanks to the kernel of the Dynkin idempotent.