Universal coverings of PL-mainfolds via coloured graphs.
On the Drazin index of regular elements
It is known that the existence of the group inverse a # of a ring element a is equivalent to the invertibility of a 2 a − + 1 − aa −, independently of the choice of the von Neumann inverse a − of a. In this paper, we relate the Drazin index of a to the Drazin index of a 2 a − + 1 − aa −. We give an alternative characterization when considering matrices over an algebraically closed field. We close with some questions and remarks.
Sur la théorie générale des demi-anneaux, I
Sur la théorie générale des demi-anneaux, II
Les μ-demi-anneaux
On the topological type of anticonformal square roots of automorphisms of Riemann surfaces.
Elements of finite order in the fundamental group of a branched cyclic covering.
Note on the degree of Cº-sufficiency of plane curves.
Let f be a germ of plane curve, we define the δ-degree of sufficiency of f to be the smallest integer r such that for anuy germ g such that j f = j g then there is a set of disjoint annuli in S whose boundaries consist of a component of the link of f and a component of the link of g. We establish a formula for the δ-degree of sufficiency in terms of link invariants of plane curves singularities and, as a consequence of this formula, we obtain that the δ-degree of sufficiency is equal to the Cº-degree...
On the Homology of Metacyclic Coverings.
On codimension one submersions of euclidean spaces.
On two recent geometrical characterizations of hyperellipticity.
We obtain short and unified new proofs of two recent characterizations of hyperellipticity given by Maskit (2000) and Schaller (2000), as well as a way of establishing a relation between them.
On the connectedness of the locus of real Riemann surfaces.
Topological types of symmetries of elliptic-hyperelliptic Riemann surfaces and an application to moduli spaces.
Sea X una superficie de Riemann de género g. Diremos que la superficie X es elíptica-hiperelíptica si admite una involución conforme h de modo que X/〈h〉 tenga género uno. La involución h se llama entonces involución elíptica-hiperelíptica. Si g > 5 entonces la involución h es única, ver [1]. Llamamos simetría a toda involución anticonforme de X. Sea Aut(X) el grupo de automorfismos conformes y anticonformes de X y σ, τ dos simetrías de X con puntos fijos y tales que {σ, hσ} y {τ, hτ} no son...
On the family of cyclic trigonal Riemann surfaces of genus 4 with several trigonal morphisms.
A closed Riemann surface which is a 3-sheeted regular covering of the Riemann sphere is called cyclic trigonal, and such a covering is called a cyclic trigonal morphism. Accola showed that if the genus is greater or equal than 5 the trigonal morphism is unique. Costa-Izquierdo-Ying found a family of cyclic trigonal Riemann surfaces of genus 4 with two trigonal morphisms. In this work we show that this family is the Riemann sphere without three points. We also prove that the Hurwitz space of pairs...
A note on isolated points in the branch locus of the moduli space of compact Riemann surfaces.
One-dimensional Hurwitz spaces, modular curves, and real forms of Belyi meromorphic functions.
Using symbolic computation in the characterization of frictional instabilities involving orthotropic materials
The present work addresses the problem of determining under what conditions the impending slip state or the steady sliding of a linear elastic orthotropic layer or half space with respect to a rigid flat obstacle is dynamically unstable. In other words, we search the conditions for the occurrence of smooth exponentially growing dynamic solutions with perturbed initial conditions arbitrarily close to the steady sliding state, taking the system away from the equilibrium state or the steady sliding...
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