Subrings invariant under endomorphisms

Let S and R be the rings of regular functions on affine algebraic varieties over a field of characteristic 0, R be embedded as a subring in S, and F : S --> S be an endomorphism such that F(R) subset R. Suppose that every ideal of height 1 in R generates a proper ideal in S, and the spectrum of R has no selfintersection points. We show that if F is an automorphism so is F|_R : R --> R. When R and S have the same transcendence degree then the fact that F|_R is an automorphisms implies that F is an automorphism.Comment: 16 page

One more proof of the Abhyankar-Moh-Suzuki theorem

We extract the Abhyankar-Moh-Suzuki theorem from the Lin-Zaidenberg theorem.Comment: 4 page

On the present state of the Andersen-Lempert theory

In this survey of the Andersen-Lempert theory we present the state of the art in the study of the density property (which means that the Lie algebra generated by completely integrable holomorphic vector fields on a given Stein manifold is dense in the space of all holomorphic vector fields). There are also two new results in the paper one of which is the theorem stating that the product of Stein manifolds with the volume density property possesses such a property as well. The second one is a meaningful example of an algebraic surface without the algebraic density property. The proof of the last fact requires Brunella's technique.Comment: 40 page