I have an offer from an elite German institute (option A) for a PhD in particle physics and artificial intelligence.
I love the project but it is not in my first choice subject: the intersection of AI and cosmology (astrophysics).
At this stage of my career; my expertise is in AI but my training is in physics/astrophysics.
I think the project and institution of option A seriously warrants considering it regardless of this. The research facility and supercomputing infrastructure are unique (the project is great also).
I will not hear back from the institutions I have applied to for other PhDs and I have already asked for an extension to the deadline of my response to option A.
I'm a good enough student, but I can't really believe I got option A and I don't think it is likely that I will get any of my other options.
This is a very stressful decision for me and I worry about whether it is possible to leave option A should I obtain another offer.
What can I do? Decline and risk missing the other opportunities to be left with nothing, or accept and always wonder what could have happened?
Thank you for any advice you might have.