I have brought some trouble onto myself I know, but what can be done by someone in my situation.
I applied and got accepted for a PhD program in Computer Science. I automatically assumed that I wanted to continue the work I did on my Master's thesis and I identified a professor who would be willing to work with me on that subject. When I got there, I reviewed the literature (there had been a few years of gap since defending my thesis) and decided I really did not like the direction the field was going in. I had been developing a new interest anyway, so I changed sub-disciplines. Now, no one will commit to be my advisor, at best maybe co-advisor with some outside expert. Part of the reason is because my school lacks experts in that area. I personally (on a friend basis) know some Computer Science professors, but none are experts in my field. What can I do? No advisor = No PhD, I know that much anyway.