\}\\ \\ \sigma_{n+0} = \inf \{ t > \eta_{n+0} : U^{u,\varepsilon}(t,\cdot) \in {\partial}B_{r_0}\} \end{array}\right.$$ with the convention that $\inf \emptyset = +\infty$. We then define the Markov chain $(Z^{u,\varepsilon}_n)_{n \in {{\mathbb N}}}$ 