Algebraically Birational Extensions

Pseudo Algebraically Closed Extensions

Simple Birational Extensions of the Polynomial Algebra

The Abhyankar-Sathaye Problem asks whether any biregular embedding φ : C →֒ C can be rectified, that is, whether there exists an automorphism α ∈ AutC such that α ◦ φ is a linear embedding. Here we study this problem for the embeddings φ : C3 →֒ C4 whose image X = φ(C3) is given in C4 by an equation p = f(x, y)u + g(x, y, z) = 0, where f ∈ C[x, y]\{0} and g ∈ C[x, y, z]. Under certain additional ...

On Pseudo Algebraically Closed Extensions of Fields

The notion of ‘Pseudo Algebraically Closed (PAC) extensions’ is a generalization of the classical notion of PAC fields. In this work we develop a basic machinery to study PAC extensions. This machinery is based on a generalization of embedding problems to field extensions. The main goal is to prove that the Galois closure of any proper separable algebraic PAC extension is its separable closure....

Simple Birational Extensions of the Polynomial Ring

The Abhyankar-Sathaye Problem asks whether any biregular embedding φ : C →֒ C can be rectified, that is, whether there exists an automorphism α ∈ AutC such that α ◦ φ is a linear embedding. Here we study this problem for the embeddings φ : C3 →֒ C4 whose image X = φ(C3) is given in C4 by an equation p = f(x, y)u + g(x, y, z) = 0, where f ∈ C[x, y]\{0} and g ∈ C[x, y, z]. Under certain additional ...

Birational Rigidity of Fano Varieties and Field Extensions

The modern study of the birational properties of Fano varieties started with the works of Iskovskikh; see the surveys [Isk01, Che05] and the many references there. A key concept that emerged in this area is birational rigidity. Let X be a Fano variety with Q-factorial, terminal singularities and Picard number 1. Roughly speaking, X is called birationally rigid if X can not be written in terms o...