Poisson fields of two variables

We study invariants and structures of Poisson fields of rational functions in two variables. For four particular families, we classify the members, establish criteria for isomorphisms and, with the exception of the Weyl Poisson field, describe the automorphism groups. Embeddings are also investigated, along with an analog of the Dixmier Conjecture: For which Poisson fields is every Poisson endomorphism an automorphism? The answer is negative for the first family, but positive answers are obtained for several subclasses of the other families. Finally, we exhibit a Poisson field which is not isomorphic to any Poisson field $\mathbb{k}(x,y)$ for which $\{x,y\}$ is a polynomial in $\mathbb{k}[x,y]$.