I am a newly admitted PhD student. When I applied for this program, I stated several research interests in my SOP. In the end, I am assigned with a supervisor whose research interests overlap with mine a bit, but not the same as my primal interest. Unfortunately, I have become more and more interested in my primal field and less in my supervisor's. My question is, how realistic to work in both? There is a post doc who is willing to guide me to work in my primal interest field, but if he leaves one or two years later, then I am afraid the work cannot be continued. Plus, I am afraid I will not be able to meet my supervisor's expectation if I do not devote all my time to his project. Moreover, since I am partially funded by my supervisor's stipend, would he mind if I work on something else? The biggest concern is that, what are the chances that my work with the post doc can lead me to a post doc position in my primal interest field 4 years later? Thank you in advance for your opinions.
