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Autor Bujalance, E. |
Documentos disponibles escritos por este autor (39)
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In this paper we get an effective algorithm to compute all odd orders and ramification indices of homeomorphisms![]()
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In this paper we obtain an effective algorithm to compute all even orders and ramification indices of homeomorphisms of finite order acting on compact surfaces, orientable or not. This completes the case of odd orders, previously studied by the [...]![]()
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Bujalance, E. ; Etayo Gordejuela, J. Javier | Department of Mathematics, Tokyo Institute of Technology | 1987If G is a group of automorphisms of a hyperelliptic Riemann surface of genus g represented as D/$\Gamma$ where D is the hyperbolic plane and $\Gamma$ a Fuchsian group, then $G\cong \Gamma '/\Gamma$ where $\Gamma$ ' is also a Fuchsian group. Furt[...]![]()
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Bujalance, E. ; Etayo Gordejuela, J. Javier ; Gamboa, J. M. | Universidad Complutense de Madrid | 1986The authors describe in terms of non-Euclidean crystallographic groups all Klein surfaces whose automorphism group is one of the following: Z/p???Z/p , Z/pq , or Z/p 2 , where p and q are distinct odd primes. This includes every nontrivial fi[...]![]()
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Let C be an algebraic curve of genus 3, defined over the real field R. The automorphism group of C is studied in this paper. In a paper by the same authors [Mich. Math. J. 33, 55-74 (1986; see 20043 below)], the hyperelliptic case was solved, th[...]![]()
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For each integer g ? 2 we give the complete list of groups acting as a group of dianalytic automorphisms of a real projective plane with g holes, which, in algebraic terms, correspond to birational automorphisms of real algebraic (M ? 1)-curves.[...]![]()
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A compact Klein surface X is called q-hyperelliptic if there is an involution $\phi$ of X such that the quotient surface $X/ $ has algebraic genus q. If X is represented as D/$\Gamma$ where D is the unit disc and $\Gamma$ a non-Euclidean crysta[...]![]()
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Bujalance, E. ; Etayo Gordejuela, J. Javier ; Gamboa, J. M. | Real Academia de Ciencias Exactas, Físicas y Naturales | 1984The classical correspondence between Riemann surfaces and complex algebraic curves, extends by the work of Ailing and Greenleaf to Klein surfaces and real algebraic curves. The topological invariants of the surface determine the ones of a smonot[...]![]()
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Elliptic-hyperelliptic, normal, unramified, double coverings of bordered hyperelliptic Klein surfaces are considered here, using methods of the theory on non-Euclidean crystallographic groups. Complete proofs will appear elsewhere![]()
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We consider double and (possibly) branched coverings : X ! X0 between real algebraic curves where X is hyperelliptic. We are interested in the topology of such coverings and also in describing them in terms of algebraic equations. In this artic[...]![]()
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Gamboa, J. M. ; Bujalance, E. ; Conder, M.D.E ; Gromadzki, G. ; Izquierdo, Milagros | Elsevier Science | 2002Let X be a Riemann surface. Two coverings p1 : X ? Y1 and p2 : X ? Y2 are said to be equivalent if p2 =’p1 for some conformal homeomorphism ’: Y1 ? Y2. In this paper we determine, for each integer g¿2, the maximum number R(g) of inequivalent ram[...]![]()
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The authors establish that an elliptic-hyperelliptic Klein surface of genus p > 5 generically has at most 4(p-1)automorphisms, excepting the case X is orientable with 2 or 4 boundary components. If X is orientable with 2 or 4 boundary componen[...]![]()
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The order of a group of automorphisms of a compact Klein surface of genus 3 with boundary does not exceed 24 [see C. L. May, Pac. J. Math. 59, 199-210 (1975; Zbl 0422.30037)]. These groups of automorphisms are quotients of NEC groups of isometri[...]![]()
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A compact Klein surface can be represented in the form D/? where D denotes the hyperbolic plane and ? a non-Euclidean crystallographic (N.E.C.) group of isometries. If ? + denotes the subgroup of orientation-preserving isometries, then D/? [...]![]()
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A Klein surface S is a surface with a dianalytic structure. If S is compact then its underlying topological surface can be orientable or nonorientable and may have boundary. The genus of S is then defined to be the genus of its canonical doub[...]![]()
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A bordered Klein surface of algebraic genus p has at most 12(p-1) automorphisms and this is attained for infinitely many values of p. Furthermore, for an infinity of values of p, the largest group of automorphisms of such a surface is $4(p+1)$ o[...]![]()
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Bujalance, E. ; Etayo Gordejuela, J. Javier ; Gamboa, J. M. ; Martens, Gerriet | Birkhäuser Verlag | 1989Let K be a compact Klein surface of algebraic genus $g\ge 2,$ which is not a classical Riemann surface. The authors show that if K admits an automorphism of order $N> 2,$ then it must have algebraic genus at least $(p\sb 1-1)N/p\sb 1$ if N is pr[...]![]()
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We consider normal (possibly) branched, finite-sheeted coverings $ \pi:X\rightarrow X'$ between hyperelliptic real algebraic curves. We are interested in the topology of such coverings and also in describing them in terms of algebraic equations.[...]![]()
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We study compact Riemann surfaces of genus g 2 having a dihedral group of automorphisms. We find necessary and sufficient conditions on the signature of a Fuchsian group for it to admit a surface kernel epimorphism onto the dihedral group DN. T[...]![]()
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A Riemann surface X is said to be of type (n,m) if its full automorphism group AutX is cyclic of order n and the quotient surface X/AutX has genus m. In this paper we determine necessary and sufficient conditions on the integers n,m,g and ?, whe[...]![]()
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Bujalance, E. ; Etayo Gordejuela, J. Javier ; Martínez, E. ; Szepietowski, B. | Cambridge Univ Press | 2015This paper is devoted to determine the connectedness of the branch loci of the moduli space of non-orientable unbordered Klein surfaces. We obtain a result similar to Nielsen's in order to determine topological conjugacy of automorphisms of prim[...]![]()
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Gamboa, J. M. ; Bujalance, E. ; Cirre, Francisco ; Gromadzki, G. | Universidad Autónoma Madrid | 2008The set of stationary points of the anticonformal involution (reflection) of a Riemann surface is called an oval. In this paper the total number of ovals of all reflections on a surface is counted provided the group of conformal automorphisms of[...]![]()
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We compute the period matrices of the Riemann surfaces given by the equations w2 = z2g+2![]()
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Every finite group acts as a group of automorphisms of some compact bordered Klein surface of algebraic genus g?2 . The same group G may act on different genera and so it is natural to look for the minimum genus on which G acts. This is the mi[...]![]()
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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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An important problem in the study of Riemann and Klein surfaces is determining their full automorphism groups. Up to now only very partial results are known, concerning surfaces of low genus or families of surfaces with special properties. This [...]![]()
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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[...]