I'm a 2nd year PhD student in a computational field. I'm about to submit my first paper on a new optimization algorithm. I've been working intensively on the problem for the last 2 years and finally managed to get the result. Besides the professor, I'm supervised by another postdoc whom I respect a lot. Although the two didn't contribute to the ideas I present in the paper, they helped me understand the field and prepare the paper. So, they deserve to be coauthors.
However, there is one man in my lab who is really ruining my mood. He is a postdoc, 15 years my senior, and has been with the lab for ages (he has a permanent position). Just for the record, he hasn't published any first or last author paper since 7 years. We are assigned by the professor to the same subgroup meeting. We use the subgroup meeting to report our individual scientific progress.
About a year ago, he came to my desk and said that I should include his name in the work I was working on because the professor said so. I was quite surprised to hear that because he had nothing to do with my project besides sitting in the same meeting. Nevertheless, I agreed because I just simply didn't care about who was on the coauthor list.
Since then, the postdoc constantly asked me to do many things for the project, which I thought didn't make any sense. I told him that he should bring up his request during the meeting when the professor is there. And every single time the response of my professor was something like "Why would you want to do that?" and his answer was "because I'm interested in it." I wish my professor would have said "then do it yourself."
About 6 months ago I came up with an idea which I thought very promising and I presented it in the subgroup meeting. The professor was away on travel, which was not unusual. The postdoc basically told me that I need to stop wasting time on my ideas and listen to his suggestions instead if I want to finish my PhD. I felt very offended and spent days and nights coding my idea. 2 months later, I got the best results that I could ever ask for. I presented the results in front of my professor and others. Everyone was happy except one man.
Today, I was trying to finish the paper and he came in. He asked me to do yet another ridiculous analysis. I told him that I cannot see why this analysis could make the paper better. Besides, this is already the final stage and everything has been discussed thoroughly with the "real" coauthors. He answered me "This might not go into the paper but I'm interested in knowing it. I'm the author and I'm allowed to make requests". My reaction was something like a silent WTF and he immediately corrected the word "author" to coauthor. I tried my best to not ask him the question "What did you contribute to the paper?"
I want to submit the paper as soon as possible but this man made me crazy. He would talk to me all day long until I do want he wants. I don't want to write to my professor (who is again traveling) to complain about him. But I'm afraid that he will use his co-authorship to keep bothering me.
What should I do?
Update: Thank you for the comments and answers. Today this man came to me again! I told him that the professor had read my draft paper, made comments, and did not tell me to do any of the work the postdoc was suggesting. I also told him that his experiments were unnecessary, since the algorithm's motivation and performance against benchmarks are already well established, and we are up against the page limit as-is. He agreed with all this, but said he still wants to do the experiments he suggested. He agreed to do it himself so as "not to bother me," but I had to spend the entire day explaining how to do it, so it actually took longer this way. I think he was just desperate to make a contribution. Lesson learned for the next project!
Update (22.August 2022): 8 years have passed since I posted the question, and it seems to still draw some attention. Thus, I want to post some updates. Good news first, the paper has been cited more than 11K times as of now. We showed that our new method performed best for the problem. We basically took the crown from the reigning champion of 10 years. For that reason, people started using our software a lot. That explains the high number of citations. Shortly after the publication, a known group in the field published a paper to independently compare our method with the former champion using their data. Their first revision was too biased towards the other method (they ran our method once and the other multiple times, taking the best result). Luckily, this did not pass the review, and they were forced to do a fair comparison. We were not the reviewers, but they sent us a draft. To our surprise, our method now looked even better in their comparison. All doubts were silenced.
Not so good news, I left science shortly after my PhD. I finished my "mission" and never planned to stay longer. Although the road was bumpy, and I had to experience to some extent the dark side of academia, I have never regretted doing the PhD. To this day, I still don't think that I would have been able to "get rid of" the unwanted coauthor because he was "assigned" to it at the very beginning. It is just how the system works. The method that finally appeared in the paper was against the will of the remaining coauthors, including my supervisor. They only accepted it when the data were presented. My task was to extend the old method by my supervisor and not inventing a new one. Nevertheless, he was fair and supportive.