Abstract:
A birational automorphism f of the projective space Pn is defined by n+1
homogeneous polynomials of the same degree d. If these polynomials have no
common divisors then d is the degree of the automorphism f. Consider the
sequence of the degrees of automorphisms f,f2,f3,... The asymptotics of
this sequence is a birational invariant of f. If the sequence is unbounded
then the automorphism has nice dynamical properties which are useful in the
study of its geometry. On the other hand, in my talk I am going to discuss the
automorphisms f such that degrees of fm are bounded above by some number;
such automorphisms are called elliptic. Blanc and Déserti proved that any
elliptic automorphism of P2 of infinite order is conjugate to a regular
automorphism of P2 in the Cremona group. I am going to tell the proof of this
assertion following their paper and then I am going to talk about attempts to
generalize this fact to a higher dimension.