Invariant quadrics and orbits for a family of rational systems of difference equations

Abstract: We study the existence of invariant quadrics for a class of systems of difference equations in ${\mathbb R}<sup>n$ defined by linear fractionals sharing denominator. Such systems can be described in terms of some square matrix $A$ and we prove that there is a correspondence between non-degenerate invariant quadrics and solutions to a certain matrix equation involving $A$. We show that if $A$ is semisimple and the corresponding system admits non-degenerate quadrics, then every orbit of the dynamical system is contained either in an invariant affine variety or in an invariant quadric.