Coloquio, 21.12.2015 a las 17:30

Hector Pasten
Harvard University; Institute for Advanced Study, Princeton, EEUU

Conjeturas sobre conjuntos Diofantinos en campos globales

No es difícil ver que los conjuntos Diofantinos de un campo global son listables, pero no es claro si el recíproco es cierto. Esto pone en evidencia la necesidad de entender la estructura de dichos conjuntos. En esta charla discutiré algunas conjeturas al respecto.
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Taller de Matemática y Cómputo, 16.10.2015 a las 16:30

Rodrigo Torres Avilés
Universidad de Concepción

Propiedades dinámicas y topológicas de Máquinas de Turing II

La charla aborda sistemas dinámicos topológicos de las máquinas de Turing, tales como TMT, TMH y t-shift, junto con propiedades aún no estudiadas en el ámbito. Se tratará la técnica demostrativa 'Embedding', y como ella nos permite estudiar tanto los conjuntos de máquinas como la decibilidad en transitividad, mixing, minimalidad y entropía topológica.
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Taller de Matemática y Cómputo, 2.10.2015 a las 16:00

Rodrigo Torres Avilés
Universidad de Concepción

Propiedades dinámicas y topológicas de Máquinas de Turing

La charla aborda sistemas dinámicos topológicos de las máquinas de Turing, tales como TMT, TMH y t-shift, junto con propiedades aún no estudiadas en el ámbito. Se tratará la técnica demostrativa 'Embedding', y como ella nos permite estudiar tanto los conjuntos de máquinas como la decibilidad en transitividad, mixing, minimalidad y entropía topológica.
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Taller de Matemática y Cómputo, 4.9.2015 a las 15:30

Christopher Thraves
Universidad de Concepción

Signed graph embedding, when everybody can sit closer to friends than enemies

Signed graphs are graphs with signed edges. They are commonly used to represent positive and negative relationships in social networks. While balance theory and clusterizable graphs deal with signed graphs, recent empirical studies have proved that they fail to reflect some current practices in real social networks. In this presentation we address the issue of drawing signed graphs and capturing such social interactions. We relax the previous assumptions to define an embedding as a model in which every vertex has to be placed closer to its neighbors connected via a positive edge than its neighbors connected via a negative edge in the resulting space. Based on this definition, we address the problem of deciding whether a given signed graph has a drawing in the 1-dimensional Euclidean space. We provide a polynomial time algorithm that decides if a given complete signed graph has a drawing, and provides it when applicable. When the input signed graph is not complete the recognition problem has been proved to be NP-complete. If we have enough time, we will show a greedy heuristic with interesting recognition capabilities when the input is not complete.
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Coloquio, 6.4.2015 a las 17:30

Jürgen Hausen
Universität Tübingen

Fano varieties with torus action

A Fano variety is an algebraic variety with an ample anticanonical divisor - from the differential point of view, these are compact Kähler manifolds with positive definite Ricci curvature. Fano varieties play a central role in the general classification theory of algebraic varieties. After a short general introduction, we briefly recall the present state of the art of the classification of toric Fano varieties, i.e. those being almost homogeneous under the action of an algebraic torus. Then we consider more generally Fano varieties with a torus action of complexity one, i.e. the general torus orbit is of codimension one. We present combinatorial tools for the study of such varieties and discuss recent classification results in the case of threefolds with at most terminal singularities.
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Coloquio, 5.3.2015 a las 15:30

Gyula Csato
TU-Dortmund (Alemania)

Results and conjectures about some isoperimetric problems with density


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