Co-authors on a study have cut communication, what can be done? During my first post-doc one of the primary researchers just dropped all communications. The upshot is that I have 3 years worth of research that I can't publish without his consent. He was initially keen to publish but when pressed to do his side of the papers he kept pushing the deadline &amp; eventually ceased communicating altogether.

OK, so that happened &amp; I moved on, I had no choice.

Unfortunately I find myself in a similar situations yet again. This time though the lack of communication is with a professor who, after coming up to a year, has not responded to my emails or phone calls. This again after an initial work division &amp; publication plan had been worked out &amp; agreed upon.

This time I do know that the prof is still working at the same place &amp; is still collaborating with the same people but just not responding to me.

What are my options here? What would you do in this situation? I am considering Union representation but is that just going to be toothless?

I have been a post doc now for 5 years &amp; I have nothing published in 4.5 years due to this kind of behaviour.
Ultimately, you can't make someone collaborate or communicate with you if they don't want to.  I think your only option is to either abandon the project, or rewrite it to remove the parts that your collaborator contributed and then publish it as solo work.  I don't see how union representation could help in any way.

I'm pretty surprised that this would happen twice, and would wonder if there's something about your interactions that might be causing it.  People usually don't voluntarily drop all contact with a collaborator unless something has happened that makes them uncomfortable to continue working with them - ethical concerns, abusive behavior, severe inability to communicate, etc.  If you have a colleague who works in the field, and you trust them to be honest with you, you might want to show them the history of your communications and see if they observe any red flags which you might not be aware of.

If you have any common acquaintances with this collaborator, they might also be able to give you some idea as to what is going on.

Normally I'd wonder if there is some involuntary reason for lack of communication - illness, personal problems, death, spam filters - but here it sounds like you've ruled those out.

Regardless of what initially caused the breakdown, I don't think your strategy of "weekly emails/calls for a year" was a good one.  I would probably send a maximum of about three messages / calls, with longer periods in between each, and the last one being an ultimatum of sorts: "if I don't hear back from you by date X, then I am going to do Y" (where Y could be stopping work on the project, or removing their contributions and proceeding, or whatever).  And then if they don't respond, you do Y, and move on with your life.  Persistence can be a virtue, but in this case I'm reminded of the saying about how insanity is when you keep doing the same thing and expect different results.  

Another tip for the future is to have multiple projects going on with multiple different collaborators, so that if one of them falls apart (either for scientific or interpersonal reasons) you still have some publications.