 Positive time change of a smooth flow

Write $\rho =1/f$ and $t={\int }_0^s\rho ({\varphi }_{r}x)dr$. For an Anosov stable bundle, the new stable directions are $v+{\lambda }_s(x,v)F(x)$, where ${\lambda }_s=\rho (x{)}^{-1}{\int }_0^{\infty }d{\rho }_{{\varphi }_{r}x}(D{\varphi }_{r}v)dr$. Exponential contraction makes this integral uniformly convergent. Differentiating the clock equation shows that its flow-direction coefficient after time $t$ is $\rho ({\varphi }_{s}x{)}^{-1}{\int }_s^{\infty }d\rho (D{\varphi }_{r}v)dr$, which decays exponentially and has the same graph form at the new point. Negative-time integrals give the unstable graph. Compactness and positivity of $f$ compare old and new times uniformly, preserving the Anosov flow property.