Dynamical Systems

Heteroclinic dynamics on the join of networks

We present a method of combining coupled cell systems to get dynamics supporting robust simple heteroclinic networks given by the product of robust simple heteroclinic networks (cycles). We consider coupled cell networks, with no assumption on symmetry, and combine them via the join operation. Assuming that the dynamics of the component networks supports robust simple heteroclinic cycles or networks, we show that the join dynamics realizes a more complex heteroclinic network given by the product of those cycles or networks.

Cancer dynamics in HIV-treated patients

Patients infected with the human immunodeficiency virus (HIV) are more vulnerable to develop various types of cancer, in particular, Hodgkin’s lymphoma, Kaposi’s sarcoma and vulvar cancer. Furthermore, cancers progression tends to be more aggressive in HIV-positive individuals than in HIV-negative ones. In this work, we develop mathematical models to describe the dynamics of cancer growth and HIV infection, when chemotherapy and treatment for HIV, namely, highly active antiretroviral therapy (HAART) are included.

Spectral Decomposition and Stability of Flows with Expansive Measures

We discuss some recent and ongoing works on the dynamics of flows with various expansive measures. In particular, we present a measurable version of the Smale’s spectral decomposition theorem for flows. More precisely, we prove that if a flow φ on a compact metric space X is invariantly measure expanding on its chain recurrent setCR(φ) and has the invariantly measure shadowing property on CR(φ) then φ has the spectral decomposition, i.e. the nonwandering set Ω(φ) is decomposed by a disjoint union of finitely many invariant and closed sets on which φ is topologically transitive.

Spectral Decomposition and Stability of Flows with Expansive Measures

We discuss some recent and ongoing works on the dynamics of flows with various expansive measures. In particular, we present a measurable version of the Smale’s spectral decomposition theorem for flows. More precisely, we prove that if a flow φ on a compact metric space X is invariantly measure expanding on its chain recurrent setCR(φ) and has the invariantly measure shadowing property on CR(φ) then φ has the spectral decomposition, i.e. the nonwandering set Ω(φ) is decomposed by a disjoint union of finitely many invariant and closed sets on which φ is topologically transitive.

Dynamical counterexamples for the usual interpretation of the Extremal Index

We consider stochastic processes arising from dynamical systems by evaluating an observable function along the orbits of the system. The Extremal Index, which is responsible for the appearance of clusters of exceedances, usually coincides with the reciprocal of the mean of the limiting cluster size distribution. In this talk, we show how to build dynamically generated stochastic processes with an Extremal Index for which that relation does not hold.

Aproximação global em Diff(S^1) e aplicações a dinâmica de grupos gerados por difeomorfismos próximos da identidade.

Discutiremos a dinâmica de grupos de difeomorfismos (analíticos) do círculo que são (localmente) não discretos. Uma técnica já bem estabelecida de aproximação desses grupos por campos de vectores locais permite uma descrição bastante detalhada das dinâmicas (extremamente caóticas) correspondentes.

The embedding problem for homeomorphisms

The embedding problems aim to describe when a certain map f (homeomorphism, diffeomorphism, etc) 

on a topological space X can be embedded in a flow with the same regularity.  There are fundamental contributions  

to the embedding problem for both the setting of homeomorphisms in low dimension (one and two) and diffeomorphisms 

dated from the fifties and the sixties, due to Anderson, Andrea, Foland, Fort, Palis, Utz and Zdun among others.