OLALLA ACOSTA , Miguel Ángel

Let v be a rank-one discrete valuation of the field Kn=k((X1,…,Xn)). We know, after [1], that if n=2 then the dimension of v is 1 and if v is the usual order function over k((X1,…,Xn)) its dimension is n−1. In this paper we prove that, in the general case, the dimension of a rank-one discrete valuation can be any number between 1 and n−1.

En la presente memoria se estudian las valoraciones discretas de rango 1 sobre un cuerpo de series en n variables con cuerpo base de característica cero. Se da una construcción explicita de un elemento de valor 1 y del cuerpo residual de cada valoración, lo que nos permite dar sus ecuaciones para métricas. Se construyen todas las ampliaciones a...

Let K → L be an algebraic field extension and ν a valuation of K. The purpose of this paper is to describe the totality of extensions {ν′} of ν to L using a refined version of MacLane's key polynomials. In the basic case when L is a finite separable extension and rk ν = 1, we give an explicit description of the limit key polynomials (which can...

In this paper we present a refined version of MacLane's theory of key polynomials, similar to those considered by M. Vaqui\'e and reminiscent of approximate roots of Abhyankar and Moh. Given a simple transcendental extension of valued fields, we associate to it a countable well-ordered set of polynomials called key polynomials. We define limit...

It is a classical result (apparently due to Tate) that all elliptic curves with a torsion point of order n (4 ≤ n ≤ 10, or n = 12) lie in a oneparameter family. However, this fact does not appear to have been used ever for computing the torsion of an elliptic curve. We present here a extremely down–to–earth algorithm using the existence of such...

Let v be a rank m discrete valuation of k[[X1,...,Xn]] with dimension n-m. We prove that there exists an inmediate extension L of K where the valuation is monomial. Therefore we compute explicitly the residue field of the valuation.

Let (R; m; k) be a local noetherian domain with field of fractions K and R_v a valuation ring, dominating R (not necessarily birationally). Let v|K be the restriction of v to K; by definition, v|K is centered at R. Let \hat{R} denote the m-adic completion of R. In the applications of valuation theory to commutative algebra and the study of...

In this paper we study rank one discrete valuations of the field k((X1, . . . , Xn)) whose center in k[[X1, . . . , Xn]] is the maximal ideal. In sections 2 to 6 we give a construction of a system of parametric equations describing such valuations. This amounts to finding a parameter and a field of coefficients. We devote section 2 to finding...

This paper deals with valuations of fields of formal meromorphic functions and their residue fields. We explicitly describe the residue fields of the monomial valuations. We also classify all the discrete rank one valuations of fields of power series in two and three variables, according to their residue fields. We prove that all our cases are...