This is going to sound really strange, but I don't want to have this question inside of me and never ask it. I love business/economics/game theory. However, the subject I've studied the most in my life at this point is physics. The question of what I want to write about for my PhD thesis is coming up and I have no ideas. Has anyone ever heard about a middle ground between physics and game theory/economics? I know it's a huge stretch, but please be considerate. I'm feel completely lost in life but I'm a firm believer that one should not allow an ego to ruin decision making. Therefore, I want to get a lot of opinions, even if people think the questions I ask are strange.