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Autor Gamboa, J. M. |
Documentos disponibles escritos por este autor (79)
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In this work we analyze some topological properties of the remainder partial derivative M := beta(s)*M\M of the semialgebraic Stone-Cech compactification beta(s)*M of a semialgebraic set M subset of R-m in order to 'distinguish' its points from [...]![]()
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In the same vein as the classical Stone–?Cech compactification, we prove in this work that the maximal spectra of the rings of semialgebraic and bounded semialgebraic functions on a semialgebraic set M ? Rn, which are homeomorphic topological sp[...]![]()
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The nature of the set of points fixed by automorphisms of Riemann or unbordered nonorientable Klein surfaces as well as quantitative formulae for them were found by Macbeath, Izquierdo, Singerman and Gromadzki in a series of papers. The possible[...]![]()
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In this article we study the most significant algebraic, topological and functorial properties of the Zariski and maximal spectra of rings of semialgebraic and bounded semialgebraic functions on a semialgebraic set.![]()
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For a formally real field K let X(K) be the space of orderings. The automorphism group Aut(K) of K operates on X(K). K is said to have the ’dense orbits property’ (DOP) if for all 2 X(K) the orbit of is dense in X(K). The study of such fields,[...]![]()
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After describing explicitly all total orderings in the ring R[[x, y]], we prove that each ordering in the quotient field of the ring of germs of real analytic functions at an irreducible point O of a real analytic surface X is defined by a half-[...]![]()
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After describing explicitly all total orderings in the ring R[[x,y]], we prove that each ordering in the quotient field of the ring of germs of real analytic functions at an irreducible point O of a real analytic surface X is defined by a half-b[...]![]()
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We compute the period matrices of the Riemann surfaces given by the equations w2 = z2g+2![]()
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We obtain new necessary conditions for an n-dimensional semialgebraic subset of R-n to be a polynomial image of R-n. Moreover, we prove that a large family of planar bidimensional semialgebraic sets with piecewise linear boundary are images of p[...]![]()
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Let R be a real closed field and n greater than or equal to 2. We prove that: (1) for every finite subset F of R", the semialgebraic set R"\F is a polynomial image of R"; and (2) for any independent linear forms 1, of R", the semialgebraic set {[...]![]()
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A one page proof (using the real spectrum) of the following result: Let f, g : X ! R be a continuous functions on a topological space X, such that f is strictly positive on g?1(0). Then there exist continuous functions u, v and w such that (1 + [...]![]()
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Alonso García, María Emilia ; Etayo Gordejuela, J. Javier ; Gamboa, J. M. ; Ruiz Sancho, Jesús María | Real Sociedad Matemática Española;Consejo Superior de Investigaciones Científicas. Instituto "Jorge Juan" de Matemáticas | 1980Dado un espacio T3? (X,T), es posible obtener una compactificación T2 del mismo, mediante ultrafiltros asociados a ciertas bases distinguidas de cerrados de (X,T) (Frink [4]). Se plantea así el problema siguiente: ¿Puede obtenerse toda compactif[...]![]()
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We present several obstructions for a subset S of Rm to be the image of an euclidean space Rn via a polynomial or a regular map f: Rn--> Rm, in terms of the "geometry" of its exterior boundary dS:=ClRm(S)\S![]()
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The author shows there is a non-Archimedean ordering of the field R(x, y), where x and y are algebraically independent over K, for which the identity is the only order-preserving automorphism. The author proves the partly known result that the f[...]![]()
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Gamboa, J. M. ; Broughton, SA ; Bujalance, E. ; Costa, F.A. ; Gromadzki, G. | American Mathematical Society | 1999For all g 2 there is a Riemann surface of genus g whose automorphism group has order 8g+8, establishing a lower bound for the possible orders of automorphism groups of Riemann surfaces. Accola and Maclachlan established the existence of such sur[...]![]()
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Gamboa, J. M. ; Broughton, SA ; Bujalance, E. ; Costa, F.A. ; Gromadzki, G. | Elsevier Science | 1996Let X be a compact Riemann surface and Aut(X) be its automorphism group. An automorphism of order 2 reversing the orientation is called a symmetry. The authors together with D. Singerman have been working on symmetries of Riemann surfaces in the[...]![]()
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Let $X$ be a compact hyperelliptic Riemann surface which admits anti-analytic involutions (also called symmetries or real structures). For instance, a complex projective plane curve of genus two, defined by an equation with real coefficients, gi[...]![]()
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Índice abreviado: 1. Generalidades. Teorema de Lagrange 2. Subgrupos normales. Homomorfismos. Teorema de estructura de los grupos abelianos finitos 3. Grupo de automorfismos. Acción de un grupo sobre un conjunto 4. El teorema de Sylow 5. Grupos [...]![]()
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Bujalance, E. ; Etayo Gordejuela, J. Javier ; Gamboa, J. M. ; Gromadzki, G. | Elsevier Science | 2011A compact Riemann surface X of genus g ? 2 which can be realized as a q-fold, normal covering of a compact Riemann surface of genus p is said to be (q, p)-gonal. In particular the notion of (2, p)-gonality coincides with p-hyperellipticity and [...]![]()
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In this paper we study the algebraic structure of the hyperelliptic mapping class group of Klein surfaces, which is closely related to the mapping class group of punctured discs. This group plays an important role in the study of the moduli spa[...]![]()
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Given a natural number p, a projective irreducible smooth algebraic curve V defined over R is called p-hyperelliptic if there exists a birational isomorphism of V, of order 2, such that V/ has genus p. This work is concerned with the existence o[...]