Artículos (Geometría y Topología)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10884

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Mostrando 1 - 20 de 213

Generalized Sasakian space forms and conformal changes of metric
(Springer, 2011-02-10) Alegre Rueda, Pablo Sebastián; Carriazo Rubio, Alfonso; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. FQM327: Geometria (Semi) Riemanniana y Aplicaciones
The study of generalized Sasakian space forms is continued in this paper. The behavior of such spaces under generalized D-conformal deformations is analyzed. As a consequence, new examples of generalized Sasakian space forms are given.
CR-submanifolds of Lorentzian manifolds
(DergiPark, 2009-04-30) Alegre Rueda, Pablo Sebastián; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. FQM327: Geometria (Semi) Riemanniana y Aplicaciones
This paper is about the talk given in the VIth Geometry Symposium in Bursa, Turkey, on July 2008. We present the notion of CR-submanifolds of a Lorentzian almost contact manifold, study their principal characteristics and the particular cases in which the manifold is Lorentzian Sasakian manifold or a Lorentzian Sasakian space form. We also presnt some new results for CR-submanifolds of a generalized Lorentzian Sasakian space form.
Structures on generalized Sasakian-space-forms
(Elsevier, 2008-06-06) Alegre Rueda, Pablo Sebastián; Carriazo Rubio, Alfonso; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. FQM327: Geometria (Semi) Riemanniana y Aplicaciones
In this paper, contact metric and trans-Sasakian generalized Sasakian-space-forms are deeply studied. We present some general results for manifolds with dimension greater than or equal to 5, and we also pay a special attention to the 3-dimensional cases.
Generalized Sasakian-space-forms
(Springer, 2004-12-01) Alegre Rueda, Pablo Sebastián; Blair, David E.; Carriazo Rubio, Alfonso; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. FQM327: Geometria (Semi) Riemanniana y Aplicaciones
Generalized Sasakian-space-forms are introduced and studied. Many examples of these manifolds are presented, by using some different geometric techniques such as Riemannian submersions, warped products or conformal and related transformations. New results on generalized complex-space-forms are also obtained.
Covering-based numbers related to the LS-category of finite spaces
(Unión Matemática Argentina, 2024-09-03) Cárdenas Escudero, Manuel Enrique; Flores Díaz, Ramón Jesús; Quintero Toscano, Antonio Rafael; Villar Liñán, María Trinidad; Universidad de Sevilla. Departamento de Geometría y Topología
In this paper, Lusternik-Schinrelmann and geometric category of finite spaces are considered. We define new numerical invariants of these spaces derived from the geometric category and present an algorithmic approach for its effective computation. The analysis is undertaken by combining homotopic features of the spaces, algorithms and tools from the theory of graphs and hypergraphs. We also provide a number of examples.
Uncountable graphs with all their vertices in one face
(Akademiai Kiado Rt., 2006) Boza Prieto, Luis; Fedriani, E.M.; Nuñez Valdés, Juan; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. Departamento de Matemática Aplicada I (ETSII)
Chartrand and Harary characterized finite outer-planar graphs, and Wagner studied uncountable graphs admitting a planar embedding. We continue this research for those outer-S graphs in surfaces S by studying un countable graphs admitting S-embeddings with all their vertices in the same face (namely, outer-S embeddings).
Outerplanarity without accumulation in the cylinder and the Möbius Band
(Board, 2013) Boza Prieto, Luis; Fedriani, Eugenio E.; Núñez Valdés, Juan; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. Departamento de Matemática Aplicada I (ETSII)
In this paper we explicitly characterize the outer-embeddings without vertex accumulation points in the open cylinder and in the Mo¨bius strip. In the first case, the list of forbidden minors consists of 11 graphs. In the second, we provide the list of 92 forbidden minors as well as the list of 182 forbidden subgraphs.
Outer-embeddability in certain pseudosurfaces arising from three spheres
(North Holland (Elsevier), 2010) Boza Prieto, Luis; Fedriani, Eugenio M.; Nuñez Valdés, Juan; Universidad de Sevilla. Departamento de Matemática Aplicada I (ETSII); Universidad de Sevilla. Departamento de Geometría y Topología
In this paper we study graph embeddings in pseudosurfaces formed by three spheres sharing at most two points each pair, and in such a way that all vertices in the graph are in the same face. Our results and examples show that the behaviour of outer embeddings in these pseudosurfaces is rather different from embeddings on the pseudosurfaces considered in the literature so far.
A new method for classifying complex filiform Lie algebras
(Elsevier Science, 2001) Boza Prieto, Luis; Fedriani, E.M.; Núñez Valdés, Juan; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. Departamento de Matemática Aplicada I (ETSII)
In this paper, we describe a new method to classify complex filiform Lie algebras based on the concept of isomorphism between Lie algebras. This method, which has the advantage of being applied to any dimension, gives the families of algebras in each dimension in an explicit way. In order to apply, only the corresponding structure the- orem of complex filiform Lie algebras in each dimension is needed. As a consequence of our study, we also predict that the increase (in terms of quotiens) in the number of algebras families when passing from even dimension to odd dimension tends to 1 whereas it grows in a no finite way if passing from odd dimension to immediate even dimension.
A Hahn-Mazurkiewicz Theorem for generalized Peano continua
(Springer, 1998) Ayala Gómez, Rafael; Chávez de Diego, María José; Quintero Toscano, Antonio Rafael; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. Departamento de Matemática Aplicada I (ETSII)
S. Mazurkiewicz remarked after his proof of the celebrated HahnMazurkiewicz Theorem ([5]) that any generalized Peano continuum is the continuous image of the half-line 0; 1 but the converse does not hold. Therefore continuous images of 0; 1 do not characterize generalized Peano continua. In this paper we use perfect maps and trees to obtain an analogue of the Hahn-Mazurkiewicz Theorem for generalized Peano continua in the spirit of the classical Hahn-Mazurkiewicz Theorem.
On the planarity of Peano generalized continua: An extension of a theorem of S. Claytor
(Institute of Mathematics, Polish Academy of Sciences, 1998) Ayala Gómez, Rafael; Chávez de Diego, María José; Quintero Toscano, Antonio Rafael; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. Departamento de Matemática Aplicada I (ETSII)
We extend a theorem of S. Claytor in order to characterize the Peano generalized continua which are embeddable into the 2-sphere. We also give a characterization of the Peano generalized continua which admit closed embeddings in the Euclidean plane.
On irreductible triangulations of Punctured Torus and Punctured Klein Bottle
(Editorial UCA, 2007) Chávez de Diego, María José; Quintero Toscano, Antonio Rafael; Villar Liñán, María Trinidad; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. Departamento de Matemática Aplicada I (ETSII)
We extend Lawrencenko and Negami’s results in [4, 5] by establishing lower and upper bounds for the number of irreducible triangulations of the punctured torus and the punctured Klein bottle.
Some Asian Women Pioneers of Chemistry and Pharmacy
(MDPI, 2022) Nuñez Valdés, Juan; Pablos Pons, Fernando de; Ramos Carrillo, Antonio; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. Departamento de Química Analítica; Universidad de Sevilla. Departamento de Farmacia y Tecnología Farmacéutica
At present, several countries on the Asian continent are still very closed off to the idea of allowing not only the work of women, but also even the fact that they can study university degrees and, after finishing them, go on to practice their professions. In addition, if we go back to the beginning of the 20th century, this situation was even more serious. However, this was not an impediment for some women from these countries to achieve their goals of pursuing higher education and then serving society with their work. This article is dedicated to showing the biographies of three of them, the Indian chemist Asima Chatterjee and Philippine pharmacists Matilde S. Arquiza and Filomena Francisco. The most relevant features of their personal and professional lives are presented and previous biographies about them are completed. The main objective of this work is to show these figures to society and hold them up as references to other people, and the methodology followed has been the search for data about their lives and work that would allow us to complete the previous existing biographies about them. A brief biography on Janaki Ammal, the first Indian woman to obtain a doctorate, is also included.
Gertrude Belle Elion, Chemist and Pharmacologist, Discoverer of Highly Relevant Active Substances
(MDPI, 2022-05) Núñez Valdés, Juan; Pablos Pons, Fernando de; Ramos Carrillo, Antonio; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. Departamento de Química Analítica; Universidad de Sevilla. Departamento de Farmacia y Tecnología Farmacéutica; Universidad de Sevilla. FQM347: Análisis Aplicado; Universidad de Sevilla. HUM371: Andalucía y América Latina: Fronteras Oceánicas, Redes Sociales, Ciudad y Territorio
Gertrude Belle Elion was a woman who had to overcome many difficulties to achieve her dream of studying to be able to cure illnesses, especially those of the heart. These difficulties were imposed both by the limited economic resources of herself and her family, which did not allow her to pay the academic fees of the university in which she wanted to enroll, as well as gender, since she also had to fight against inequalities of that type prevalent in the society of her time. However, and despite these obstacles, she managed to graduate in Chemistry, based on interest, effort and tenacity, and later began a research career full of successes, which led her to discover relevant active substances which allow her to be awarded the Nobel Prize in Physiology or Medicine in 1988. This article presents the most relevant features of her personal and professional life and completes previous biographies about her life. Its main objective is to reintroduce her to society and put her as a reference to other people. The methodology followed has been the search for those data about her life and work that would allow completing the previous existing biographies about her.
Análisis de errores en la conceptualización y simbolización de ecuaciones diferenciales en alumnos de química
(Grupo editorial Iberoamérica, 1996-08) Villar Liñán, María Trinidad; Llinares, Salvador; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. FQM326: Geometria Diferencial y Teoria de Lie
Este artículo recoge un análisis de los errores más frecuentes cometidos por estudiantes de Matemáticas de 2° curso de la Licenciatura de Química (Universidad de Sevilla, España) en el trabajo con Ecuaciones Diferenciales (ED). Los errores se han tornado de las respuestas que los alumnos dieron a tres cuestiones relativas a ED (diseñadas expresamente para este trabajo) y que recogen diferentes aspectos puramente matemáticos: definir, ejemplificar y modelizar. Las respuestas se clasificaron atendiendo a dos criterios: según las nociones reflejadas en la definición de ED y según las características de los ejemplos dados. Además analizamos relaciones entre ambas categorías. Identificar y analizar errores puede ayudamos a localizar obstáculos en la formación de conceptos y a detectar dificultades que nuestros alumnos encuentran al realizar tareas propuestas.
Weak- Z-Structures and one-relator groups
(ScienceDirect, 2022-07-22) Cárdenas Escudero, Manuel Enrique; Fernández Lasheras, Francisco Jesús; Quintero Toscano, Antonio Rafael; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. FQM189: Homotopia Propia
Motivated by the notion of boundary for hyperbolic and groups, Bestvina [2] introduced the notion of a (weak) -structure and (weak) -boundary for a group G of type (i.e., having a finite complex), with implications concerning the Novikov conjecture for G. Since then, some classes of groups have been shown to admit a weak -structure (see [15] for example), but the question whether or not every group of type admits such a structure remains open. In this paper, we show that every torsion free one-relator group admits a weak -structure, by showing that they are all properly aspherical at infinity; moreover, in the 1-ended case the corresponding weak -boundary has the shape of either a circle or a Hawaiian earring depending on whether the group is a virtually surface group or not. Finally, we extend this result to a wider class of groups still satisfying a Freiheitssatz property.
A topological equivalence relation for finitely presented groups
(ScienceDirect, 2020-01-07) Cárdenas Escudero, Manuel Enrique; Fernández Lasheras, Francisco Jesús; Quintero Toscano, Antonio Rafael; Roy, R.; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. FQM189: Homotopia Propia
In this paper, we consider an equivalence relation within the class of finitely presented discrete groups attending to their asymptotic topology rather than their asymptotic geometry. More precisely, we say that two finitely presented groups G and H are “proper 2-equivalent” if there exist (equivalently, for all) finite 2-dimensional CW-complexes X and Y, with and , so that their universal covers and are proper 2-equivalent. It follows that this relation is coarser than the quasi-isometry relation. We point out that finitely presented groups which are 1-ended and semistable at infinity are classified, up to proper 2-equivalence, by their fundamental pro-group, and we study the behavior of this relation with respect to some of the main constructions in combinatorial group theory. A (finer) similar equivalence relation may also be considered for groups of type , which captures more of the large-scale topology of the group. Finally, we pay special attention to the class of those groups G which admit a finite 2-dimensional CW-complex X with and whose universal cover has the proper homotopy type of a 3-manifold. We show that if such a group G is 1-ended and semistable at infinity then it is proper 2-equivalent to either , or (here, is the free group on two generators). As it turns out, this applies in particular to any group G fitting as the middle term of a short exact sequence of infinite finitely presented groups, thus classifying such group extensions up to proper 2-equivalence.
Lifting Semistability in Finitely Generated Ascending HNN-Extensions
(Association des Annales de l'Institut Fourier, 2023-07-03) Fernández Lasheras, Francisco Jesús; Mihalik, Michael; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. FQM189: Homotopia Propia
If a finitely generated group G maps epimorphically onto a group H, we are interested in the question: When does the semistability of H imply G is semistable? In this paper, we give an answer within the class of ascending HNNextensions. More precisely, our main theorem states: Suppose that the 1-ended finitely generated ascending HNN-extension H = ⟨S, t; R, t−1st = ϕ(s), s ∈ S⟩ is semistable at infinity. Let R be the kernel of the obvious homomorphism from the free group F({t} ∪ S) onto H, then there is a finite subset R0 ⊆ R such that those finitely generated ascending HNN-extensions H1 = ⟨S, t; R1, t−1st = ϕ(s), s ∈ S⟩, with R0 ⊆ R1 ⊂ R, are all 1-ended and semistable at infinity as well. Furthermore H1 has such a presentation with R1 ⊂ R. Note that there is an obvious epimorphism from H1 to H. It is unknown whether all finitely presented ascending HNN-extensions are semistable at infinity.
Proper 2–equivalences between infinite ended finitely presented groups
(Mathematical Sciences Publishers, 2023-03-27) Cárdenas Escudero, Manuel Enrique; Fernández Lasheras, Francisco Jesús; Quintero Toscano, Antonio Rafael; Ranja, R.; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. FQM189: Homotopia Propia
Recall that two finitely presented groups G and H are “proper 2–equivalent” if they can be realized by finite 2–dimensional CW–complexes whose universal covers are proper 2–equivalent as (strongly) locally finite CW–complexes. This purely topological relation is coarser than the quasi-isometry relation, and those groups which are 1–ended and semistable at infinity are classified, up to proper 2–equivalence, by their fundamental pro-group. We show that if G and H are proper 2–equivalent and semistable at each end, then any two finite graph of groups decompositions of G and H with finite edge groups and finitely presented vertex groups with at most one end must have the same set of proper 2–equivalence classes of (infinite) nonsimply connected at infinity vertex groups (without multiplicities). Moreover, those simply connected at infinity vertex groups in such a decomposition (if any) are all proper 2–equivalent to Z Z Z. Thus, under the semistability hypothesis, this answers a question concerning the classification of infinite ended finitely presented groups up to proper 2–equivalence, and shows again the behavior of proper 2–equivalences versus quasi-isometries, in which the geometry of the group is taken into account.
Quasi-isometries and proper homotopy: The quasi-isometry invariance of proper 3-realizability of groups
(American Mathematical Society, 2019-04-01) Cardenas Escudero, Manuel; Fernández Lasheras, Francisco Jesús; Quintero Toscano, Antonio Rafael; Roy, R.; Universidad de Sevilla. Departamento de Geometría y Topología; Universidad de Sevilla. FQM189: Homotopia Propia
We recall that a finitely presented group G is properly 3-realizable if for some finite 2-dimensional CW-complex X with π1(X) ∼= G, the universal cover X has the proper homotopy type of a 3-manifold. This purely topological property is closely related to the asymptotic behavior of the group G. We show that proper 3-realizability is also a geometric property meaning that it is a quasi-isometry invariant for finitely presented groups. In fact, in this paper we prove that (after taking wedge with a single n-sphere) any two infinite quasiisometric groups of type Fn (n ≥ 2) have universal covers whose n-skeleta are proper homotopy equivalent. Recall that a group G is of type Fn if it admits a K(G, 1)-complex with finite n-skeleton.

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