Before we can prove further results about $e^{-2t}$ convergence rate, we need to show that $v(t) \to e^\nu$ at $e^{-t}$ rate. For some reason, Theorem 11.3.3 falls short. An idea to use Theorem 11.3.4. We need to prove the present theorem and also the case where $f \in BC_\ell$. Then what we can do is to multiply both sides of the integral equations for $x(t)$ by $e^t$ and to show that this approaches a constant. Ultimately, what we want to do is to show that $v(t)$ and $v\prime(t)$ has the desired asymptotic expansion.
Before we can prove further results about $e^{-2t}$ convergence rate, we need to show that $v(t) \to e^\nu$ at $e^{-t}$ rate. For some reason, Theorem 11.3.3 falls short. An idea to use Theorem 11.3.4. We need to prove the present theorem and also the case where $f \in BC_\ell$. Then what we can do is to multiply both sides of the integral equations for $x(t)$ by $e^t$ and to show that this approaches a constant. Ultimately, what we want to do is to show that $v(t)$ and $v\prime(t)$ has the desired asymptotic expansion.