Estudaremos uma fam lia de endomor smos bi-dimensionais, constru da por Marcelo
Viana em [Vi97], de atratores n~ao-uniformemente hiperb olicos com sensibilidade as
condi c~oes iniciais, em outras palavras, pontos na bacia de atra c~ao tem apenas expoentes
de Lyapunov positivos. Estes sistemas tamb em ilustram um novo mecanismo robusto de
din^amica sens vel. Apesar do car ater n~ao-uniforme da expans~ao, o atrator persiste numa
vizinhan ca do mapa inicial.
We will study a family of two-dimensional endomorphisms built by Marcelo Viana
in [Vi97], of non-uniformly hyperbolic attractors with sensitivity to initial conditions, in
other words, points in the basin of attraction have only positive Lyapunov exponents.
These systems also illustrate a new robust mechanism of sensitive dynamics. In spite of
the non-uniform expansion, the attractor persists in a neighborhood of the initial map.
