Let f:A2→A2 be a polynomial automorphism of dynamical degree δ≥2 over a number field K
Nearby in the stack
. (This is equivalent to say that
f
is a polynomial automorphism that is not triangularizable.) Then we construct canonical height functions defined on
A2(Kˉ)
associated with
f
. These functions satisfy the Northcott finiteness property, and an
Kˉ
-valued point on
A2(Kˉ)
is
f
-periodic if and only if its height is zero. As an application of canonical height functions, we give an estimate on the number of points with bounded height in an infinite