DEPARTAMENTO DE MATEMÁTICA – CFM / UFSC

Seminário em Análise Convexa e Otimização

Desempenho de algorítmos de máximo declive para a minimização de funções quadráticas

Expositor: Clóvis C. Gonzaga – Departamento de Matemática, UFSC

Data – Hora: 11/05/2016 – 10h30

Local: Sala 202, Departamento de Matemática

Maiores informações

Seminario de Matematica Aplicada

Consistent volumetric discretizations inside self-intersecting surfaces

Palestrante: Leonardo Koller Sacht, Departamento de Matemática, UFSC

Resumo: Decades of research have culminated in a robust geometry processing pipeline for surfaces. Most steps in this pipeline, like deformation, smoothing, subdivision and decimation, may create self-intersections. Volumetric processing of solid shapes then becomes difficult, because obtaining a correct volumetric discretization is impossible: existing tet-meshing methods require watertight input. We propose an algorithm that produces a tetrahedral mesh that overlaps itself consistently with the self-intersections in the input surface. This enables volumetric processing on self-intersecting models. We leverage conformalized mean-curvature flow, which removes self-intersections, and define an intrinsically similar reverse flow, which prevents them. We tetrahedralize the resulting surface and map the mesh inside the original surface. We demonstrate the effectiveness of our method with applications to automatic skinning weight computation, physically based simulation and geodesic distance computation.

Local: Auditório (LAED) do Departamento de Matemática, andar térreo
Dia – Horário: 12/05/2016 – 14:00h

LINK

Seminários em Geometria e Topologia

“On the rigidity problem for geodesically complete Brinkmann gravitational waves”

Palestrante: Jonatan Herrera (UFSC)

Resumo: Since the appearence of the so-called singularity theorems, the gravitational collapse, as happen in black holes and the Big Bang, has been described by geodesic incompleteness of null or timelike geodesics. As gravity is naturally thought as an atractive force, gravitational collapse should be rather common. This lead to the conjecture of Geroch that solutions of Einstein field equations geodesically complete should be scarce.

In this sense, Anderson proved in 2000 the following remarkable result about solutions of the vacuum Einstein equations: any 4-dimensional stationary spacetime without closed timelike curves, Ricci-flat and geodesically complete should be isometric to a quotient of the Minkowski model.

My aim in this seminar is to present a recent work, in collaboration with Ivan P. Costa e Silva (UFSC) and José Luis Flores (UMA), where we prove a null analog of Anderson’s result. Concretely, I will show that any 4-dimensional Brinkmann model, strongly causal, Ricci-flat, geodesically complete and transversally Killing is isometric to a plane wave. I will also discuss about the relation of this rigidity problem and the well-known Elhers Kundt conjecture on pp-waves.

Dia – Horário: 13/05/2016 – 15:30
Local: Auditório do Departamento de Matemática (LAED)

Colóquio de Matemática

Título: Objetos (Bi)Galois e certas bicategorias

Palestrante: Dra. Luz Adriana Mejia Castaño (UFSC)

Resumo: Na teoria das álgebras de Hopf, há uma família de comodulos muito importante, eles são chamados objetos de Galois. Suas utilidades são variadas. Nesta palestra, eu vou mostrar dois resultados de classificação. O primeiro resultado permite classificar certos funtores monoidais exceto equivalência natural (devido a Schauenburg-1991). O segundo resultado permite classificá-los exceto equivalência pseudo-natural (devido a Femic, Mejia, Mombelli-2014).

Local: Sala MTM 007

Dia/Horário: 06 de maio de 2016 / 14:00h

Cartaz

Seminário de Matemática Aplicada

Alguns desafios para implementação de métodos numéricos em espaços de Banach

Palestrante: Fábio Margotti, Departamento de Matemática, UFSC

Local: Auditório (LAED) do Departamento de Matemática, térreo.
Dia – Horário: Quinta-feira, 05/05/2016 – 14:00