Poisson bracket, deformed bracket and gauge group actions in Kontsevich deformation quantization

We express the difference between Poisson bracket and deformed bracket for Kontsevich deformation quantization on any Poisson manifold by means of second derivative of the formality quasi-isomorphism. The counterpart on star products of the action of formal diffeomorphisms on Poisson formal bivector fields is also investigated.Comment: 11 pages, one xypic figure. Minor changes on section I