<p>I would strongly suggest you not double major if you’re serious about getting a PhD in math. Unless you want to work in a field that specifically correlates with another major, for example mathematical physics and physics, theoretical computer science or computer science, or logic and philosophy, honestly, a double major would hurt you. You would be much better off using extra space to take more math classes, especially since math is a field that’s very deep, so you need a lot of background knowledge to be successful at doing research.</p>
<p>Is there any specific reason you want to double major in something? In my experience most people who double major do so either to try to build their resume or look really impressive, or because they want to prove that their interests are diverse. And to be frank, if you don’t even know what you want to double major in, then you probably don’t have a good reason to do so. Even if you find out that you want to do logic, for example, you would probably be better off taking philosophy classes as electives, rather than going through the hassle of being a double major.</p>