Published online by Cambridge University Press: 07 July 2022
We formulate a strengthening of the Zariski dense orbit conjecture for birational maps of dynamical degree one. So, given a quasiprojective variety X defined over an algebraically closed field K of characteristic $0$, endowed with a birational self-map
$\phi $ of dynamical degree
$1$, we expect that either there exists a nonconstant rational function
$f:X\dashrightarrow \mathbb {P} ^1$ such that
$f\circ \phi =f$, or there exists a proper subvariety
$Y\subset X$ with the property that, for any invariant proper subvariety
$Z\subset X$, we have that
$Z\subseteq Y$. We prove our conjecture for automorphisms
$\phi $ of dynamical degree
$1$ of semiabelian varieties X. Moreover, we prove a related result for regular dominant self-maps
$\phi $ of semiabelian varieties X: assuming that
$\phi $ does not preserve a nonconstant rational function, we have that the dynamical degree of
$\phi $ is larger than
$1$ if and only if the union of all
$\phi $-invariant proper subvarieties of X is Zariski dense. We give applications of our results to representation-theoretic questions about twisted homogeneous coordinate rings associated with abelian varieties.
The authors were partially supported by Discovery Grants from the National Science and Engineering Research Council of Canada.