Abstract
We study weak hyperbolicity of a differentiable dynamical system which is robustly free of non-hyperbolic periodic orbits of Markus type. Let S be a C1-class vector field on a closed manifold Mn, which is free of any singularities. It is of C1-weak-star in case there exists a C1-neighborhood $¥mathscr{U}$ of S such that for any X ∈ $¥mathscr{U}$, if P is a common periodic orbit of X and S with S↾ P = X↾ P, then P is hyperbolic with respect to X. We show, in the framework of Liao theory, that S possesses the C1-weak-star property if and only if it has a natural and nonuniformly hyperbolic dominated splitting on the set of periodic points Per(S), for the case n = 3.