Someone (call him Peter) contributed to part of a paper I've written. This occurred over the course of numerous emails (we've never met in person). I am including those results in the paper, and Peter is aware of this. I asked Peter multiple times to be coauthor but he never responded to that request. I'm ready to submit the paper now.
(1) Can I submit the paper? I should be able to add Peter as coauthor if he responds while the paper is being reviewed.
(2) Do I have to submit the paper with Peter's name, or can I submit with a a simple acknowledgement?