How to handle Collaboration with a Senior Mathematician, Postdoctoral Advisor or your Doctoral Advisor?
Especially if the senior person is male, but even if not, there are likely to be tacit and perhaps unconscious assumptions that you are not the driving or even an equal force in the collaboration. This may be absolutely contrary to the facts but still difficult to handle, and critically so at the start of your career when you do not have other collaborations. Try to come up with a good strategy for your particular circumstances. With luck, your senior collaborator will be open to giving useful advice (but credit issues are always delicate, so tread carefully).
See also Dianne O'Leary's post regarding tenure and collaboration with one's advisor.
In my case, a career-long collaboration with my advisor (also in my department!) undoubtedly triggered these assumptions to some extent. I took the view that really good work was getting done and should not be sacrificed, especially since the collaboration was amicable. In time, I established a number of other rewarding collaborations.
See also Marie Vitulli's post regarding collaboration with colleagues.
See also Krishnan Shankar's post regarding domineering collaborators and making yourself heard.