Información del autor
Documentos disponibles escritos por este autor (48)
Añadir el resultado a su cesta Hacer una sugerencia Refinar búsqueda
texto impreso
texto impreso
We determine all complete intersection surface germs whose Pythagoras number is 2, and find that they are all embedded in R-3 and have the property that every positive semidefinite analytic function germ is a sum of squares of analytic function [...]texto impreso
Baro González, Elías ; Fernando Galván, José Francisco ; Ruiz Sancho, Jesús María | Elsevier | 2014-09This paper is devoted to the approximation of differentiable semialgebraic functions by Nash functions. Approximation by Nash functions is known for semialgebraic functions defined on an affine Nash manifold M, and here we extend it to functions[...]texto impreso
texto impreso
En este trabajo obtemos algunos resultados básicos sobre determinación finita y clasificación de singularidades para series con coeficientes en un cuerpo de características cero. Estos resultados son clásicos para coeficientes complejos, y reale[...]texto impreso
texto impreso
In this work, we study the structure of non-refinable chains of prime ideals in the (real closed) rings S(M) and S*(M) of semialgebraic and bounded semialgebraic functions on a semialgebraic set M subset of R-m. We pay special attention to the p[...]texto impreso
In this work, we study the structure of non-refinable chains of prime ideals in the (real closed) rings s(M) and s*(M) of semialgebraic and bounded semialgebraic functions on a semialgebraic set M??m. We pay special attention to the prime z-idea[...]texto impreso
In this work we prove constructively that the complement $\R^n\setminus\pol$ of a convex polyhedron $\pol\subset\R^n$ and the complement $\R^n\setminus\Int(\pol)$ of its interior are regular images of $\R^n$. If $\pol$ is moreover bounded, we ca[...]texto impreso
In this work we prove constructively that the complement Rn \ K of a convex polyhedron K ? Rn and the complement Rn \ Int(K) of its interior are regular images of Rn. If K is moreover bounded, we can assure that Rn \ K and Rn \ Int(K) are also p[...]texto impreso
Fernando Galván, José Francisco ; Gamboa, J. M. ; Ueno, Carlos | Oxford University Press (OUP) | 2011We show that convex polyhedra in R(n) and their interiors are images of regular maps R(n) -> R(n). As a main ingredient in the proof, given an n-dimensional, bounded, convex polyhedron K subset of R(n) and a point p is an element of R(n) \ K, w[...]texto impreso
Acquistapace, Francesca ; Broglia, Fabrizio ; Fernando Galván, José Francisco | Springer Verlag | 2009We consider several modified versions of the Positivstellensatz for global analytic functions that involve infinite sums of squares and/or positive semidefinite analytic functions. We obtain a general local-global criterion which localizes the o[...]texto impreso
Acquistapace, Francesca ; Broglia, Fabrizio ; Fernando Galván, José Francisco | Springer | 2015-12-17In this work we present the concept of C-semianalytic subset of a real analytic manifold and more generally of a real analytic space. C-semianalytic sets can be understood as the natural generalization to the semianalytic setting of global analy[...]texto impreso
Acquistapace, Francesca ; Broglia, Fabrizio ; Fernando Galván, José Francisco | SCUOLA NORMALE SUPERIORE DI PISA | 2014In this work, we present "infinite" multiplicative formulae for countable collections of sums of squares (of meromorphic functions on R-n). Our formulae generalize the classical Pfister's ones concerning the representation as a sum of 2(r) squar[...]texto impreso
Among the invariant factors g of a positive semidefinite analytic function f on R-3, those g whose zero set Y is a curve are called special. We show that if each special g is a sum of squares of global meromorphic functions on a neighbourhood of[...]
