On the dynamics of the Euler equations on so(4)

This paper deals with the Euler equations on the Lie Algebra so(4). These equations are given by a polynomial differential system in R6. We prove that this differential system has four 3-dimensional invariant manifolds and we give a complete description of its dynamics on these invariant manifolds. In particular, each of these invariant manifolds are fulfilled by periodic orbits except in a zero Lebesgue measure set

Center boundaries for planar piecewise-smooth differential equations with two zones

Agraïments: The first author is partially supported by Procad-Capes88881.068462/2014-01 and FAPESP2013/24541-0. The second author is partially supported by program CAPES/PDSE grant number 7038/2014-03 and CAPES/DS program number 33004153071P0. The third author is supported by program CAPES/PNPD grant number 1271113.This paper is concerned with 1-parameter families of periodic solutions of piecewise smooth planar vector fields, when they behave like a center of smooth vector fields. We are interested in finding a separation boundary for a given pair of smooth systems in such a way that the discontinuous system, formed by the pair of smooth systems, has a continuum of periodic orbits. In this case we call the separation boundary as a center boundary. We prove that given a pair of systems that share a hyperbolic focus singularity p 0 , with the same orientation and opposite stability, and a ray Σ 0 with endpoint at the singularity p 0 , we can find a smooth manifold Ω such that Σ 0 ∪ p 0 ∪ Ω is a center boundary. The maximum number of such manifolds satisfying these conditions is five. Moreover, this upper bound is reached

Cuando la forma importa: uso de un modelo matemático simple para estimar los tamaños de áreas críticas en la conservación.

Pág. 12 – 26, gráficos, tablas, fórmulas, imágenes.In the analysis of anthropogenic impact on the environment arises the question of whether the shapes of preserved habitat fragments play an important role in the conservation of wild species. In this work we use a very simple mathematical model based on a reaction-diffusion equation to analyze the effects of geometric shape and area on the permanence of populations in habitat fragments. Our results indicate that a dimensionless quantity calculated from a combination of biological variables is the main component that determines if the species survives in the preserved fragment and whether its geometric shape is important. We provide a methodology to calculate critical area sizes for which population size is most affected by fragment shape. The methodology is illustrated in a preliminary study, in which the model is used to estimate threshold area sizes for habitat fragments of a threatened species Sapajus xanthosternos.REVISTA DE MODELAMIENTO MATEMÁTICO DE SISTEMAS BIOLÓGICOS - MMSB, VOL. 2, No.

Variedade central para laços homoclínicos

O objetivo principal desse trabalho é provar, sob certas hipóteses de transversalidade e sobre os autovalores, que se uma família a um-parâmetro de equações diferenciais possuindo, para um determinado valor do parâmetro, um laço homoclínico conectado a um ponto de equilíbrio do tipo sela, então existe uma variedade central invariante, de dimensão dois, que contém o laçco homoclínico, que contém todas as trajetórias que permanecem numa vizinhança do laço homoclínico e ainda é tangente ao autoespaço gerado por autovetores associados aos autovalores que determinam o laço homoclínico.The main goal of this work is to prove, under certain hypothesis of transversality and about the eigenvalues, that if a one-parameter family of ordinary differential equations possess, for a determined value of the parameter, a homoclinic loop connected to an equilibrium point of type saddle, then there exists an invariant center manifold, of dimension two, that contains the homoclinic loop, that contains all trajectories which stay in a small neighborhood of the homoclinic loop and that is tangent to the eigenspace spanned by the eigenvectors associated to the eigenvalues that determine the homoclinic loop

On the dynamics of the Euler equations on so(4)

This paper deals with the Euler equations on the Lie Algebra so(4). These equations are given by a polynomial differential system in R6. We prove that this differential system has four 3-dimensional invariant manifolds and we give a complete description of its dynamics on these invariant manifolds. In particular, each of these invariant manifolds are fulfilled by periodic orbits except in a zero Lebesgue measure set

Center boundaries for planar piecewise-smooth differential equations with two zones

Agraïments: The first author is partially supported by Procad-Capes88881.068462/2014-01 and FAPESP2013/24541-0. The second author is partially supported by program CAPES/PDSE grant number 7038/2014-03 and CAPES/DS program number 33004153071P0. The third author is supported by program CAPES/PNPD grant number 1271113.This paper is concerned with 1-parameter families of periodic solutions of piecewise smooth planar vector fields, when they behave like a center of smooth vector fields. We are interested in finding a separation boundary for a given pair of smooth systems in such a way that the discontinuous system, formed by the pair of smooth systems, has a continuum of periodic orbits. In this case we call the separation boundary as a center boundary. We prove that given a pair of systems that share a hyperbolic focus singularity p 0 , with the same orientation and opposite stability, and a ray Σ 0 with endpoint at the singularity p 0 , we can find a smooth manifold Ω such that Σ 0 ∪ p 0 ∪ Ω is a center boundary. The maximum number of such manifolds satisfying these conditions is five. Moreover, this upper bound is reached