Let $t \in \mathbf{R}_+$. Show that if $f \in C^0(\mathbf{R}) \cap CL(\mathbf{R})$, then $P_t(f) \in C^0(\mathbf{R})$. Also show that $P_t(f)$ is bounded in absolute value by a polynomial function in $|x|$ independent of $t$. Deduce that $P_t(f) \in L^1(\varphi)$.
Let $t \in \mathbf{R}_+$. Show that if $f \in C^0(\mathbf{R}) \cap CL(\mathbf{R})$, then $P_t(f) \in C^0(\mathbf{R})$. Also show that $P_t(f)$ is bounded in absolute value by a polynomial function in $|x|$ independent of $t$. Deduce that $P_t(f) \in L^1(\varphi)$.