The group of tame automorphisms. The group Aut($\mathbb{A}^{n}$) of polynomial automorphisms of the a ne space is an interesting huge group, and a slightly simpler group is its subgroup Aut($\mathbb{A}^{n}$) of tame automorphisms. Natural questions about these groups include:– does they admit normal subgroups beside the obvious subgroup of automorphisms with Jacobian 1?– do they satisfy a Tits alternative?– what are the possible dynamical degrees of their elements? The method to investigate these questions is via some actions on some metric spaces, namely the coset complex and the valuation complex, that we plan to introduce in detail. The lectures will focus on the following three cases: the group Aut($\mathbb{A}^{2}$) = Tame($\mathbb{A}^{2}$) following Chapter 7 of my book in preparation, then the group Tame($\mathbb{A}^{3}$) (Lamy, LamyPrzytycki, Blanc-Van Santen), and finally the group Tame(Q($\mathbb{A}^{4}$)) of tame automorphisms of $\mathbb{A}^{4}$ preserving a nondegenerate quadratic form (Bisi-Furter-Lamy, Martin, Dang).[-]

The preceding Etats de la recherche on this topic happened in Rennes, 2006, and the organizers of the present edition asked me to make the bridge between these two sessions. My 2006 talks were devoted to the theory of heights and equidistribution theorems for algebraic dynamical systems. I will start from there by presenting the framework allowed by Arakelov geometry, and explaining the recent manuscript of X. Yuan and S.-W. Zhang who provide a birational perspective to these concepts. The theory is a bit complex and technical but I will try to emphasize the parallel between those ideas and the ones that lie at the ground of pluripotential theory in complex analysis, or in the theory of b-divisors in algebraic geometry.[-]

The group Aut($\mathbb{A}^{n}$) of polynomial automorphisms of the a ne space is an interesting huge group, and a slightly simpler group is its subgroup Aut($\mathbb{A}^{n}$) of tame automorphisms. Natural questions about these groups include:– does they admit normal subgroups beside the obvious subgroup of automorphisms with Jacobian 1?– do they satisfy a Tits alternative?– what are the possible dynamical degrees of their elements? The method to investigate these questions is via some actions on some metric spaces, namely the coset complex and the valuation complex, that we plan to introduce in detail. The lectures will focus on the following three cases: the group Aut($\mathbb{A}^{2}$) = Tame($\mathbb{A}^{2}$) following Chapter 7 of my book in preparation, then the group Tame($\mathbb{A}^{3}$) (Lamy, LamyPrzytycki, Blanc-Van Santen), and finally the group Tame(Q($\mathbb{A}^{4}$)) of tame automorphisms of $\mathbb{A}^{4}$ preserving a nondegenerate quadratic form (Bisi-Furter-Lamy, Martin, Dang).[-]

The group of tame automorphisms. The group Aut($\mathbb{A}^{n}$) of polynomial automorphisms of the a ne space is an interesting huge group, and a slightly simpler group is its subgroup Aut($\mathbb{A}^{n}$) of tame automorphisms. Natural questions about these groups include:– does they admit normal subgroups beside the obvious subgroup of automorphisms with Jacobian 1?– do they satisfy a Tits alternative?– what are the possible dynamical degrees of their elements? The method to investigate these questions is via some actions on some metric spaces, namely the coset complex and the valuation complex, that we plan to introduce in detail. The lectures will focus on the following three cases: the group Aut($\mathbb{A}^{2}$) = Tame($\mathbb{A}^{2}$) following Chapter 7 of my book in preparation, then the group Tame($\mathbb{A}^{3}$) (Lamy, LamyPrzytycki, Blanc-Van Santen), and finally the group Tame(Q($\mathbb{A}^{4}$)) of tame automorphisms of $\mathbb{A}^{4}$ preserving a nondegenerate quadratic form (Bisi-Furter-Lamy, Martin, Dang).[-]

We discuss the idea of renormalization for complex dynamical systems. There various types of renormalizations defined via a first return map, appear in complex dynamics, for unimodal maps, homeomorphisms of circle, and germs of irrationally indifferent fixed points of holomorphic maps. The target of renormalization is usually tame and fragile dynamics and the connecting maps are often expanding maps and the exding property helps us to understand the rigid nature of the target maps. We propose the idea of dynamical charts for irrationally indifferent fixed points, in order to reconstruct the original map from the sequence of renormalizations.[-]