I've been trying to learn about Dirichlet series, in particular from Apostol's IANT textbook.
The textbooks tend to present result and not discuss them narratively, so I am left unsure of my correct understandanding of the results.
Are the following summary statements a correct interpretation of Apostol's IANT:
- If a Dirichlet series $\sum_{n \leq x} a_n/n^s$ is bounded at complex $s_0=\sigma_0+it_0$ then it is also bounded at $s_1=\sigma_1+it_1$ where $\sigma_1>\sigma_0$.
- If a Dirichlet series $\sum_{n \leq x} a_n/n^s$ is bounded at complex $s_0=\sigma_0+it_0$ then it also converges when $x\rightarrow \infty$ at $s_1=\sigma_1+it_1$ where $\sigma_1>\sigma_0$.
- If $\sum_{n \leq x} a_n$ is bounded, then the Dirichlet series $\sum a_n/n^s$ converges for $\sigma>0$.