From the Lie Operad to the Grothendieck–Teichmüller Group

We study the deformation complex of the natural morphism from the degree d shifted Lie operad to its polydifferential version, and prove that it is quasi-isomorphic to the Kontsevich graph complex GCd. In particular, we show that in the case d = 2 the Grothendieck–Teichmüller group GRT1 is a symmetry group (up to homotopy) of the aforementioned morphism. We also prove that in the case d = 1, corresponding to the usual Lie algebras, the natural morphism admits a unique homotopy non-trivial deformation, which is described explicitly with the help of the universal enveloping construction. Finally, we prove the rigidity of the strongly homotopy version of the universal enveloping functor in the Lie theory.