I have already finished my PhD at X university. I am now a postdoc at Y university and in collaboration with X university (by "in collaboration with X" I mean that I actually have two supervisors: one from Y and one from X).
Only Y is paying for me, and, I am currently working in the lab at Y university. But my affiliation is X and Y in the scientific papers. My supervisor at Y accepted that I also use the affiliation X.
As I am using two affiliations X and Y in my scientific papers, can I consider that I am a postdoc at two universities at the same time? Is it possible that I write in my CV that I am a postdoc at two universities even that X is not paying for me?
Any help will be very appreciated.