I've taken the typical undergraduate physics program required math: calculus series, linear algebra, Diff Eq (this fall, 2012), and an extra mathematical reasoning/proof writing class. I need a few more maths to complete my physics degree and pick up a math minor, and to prepare for physics grad school. The plan was to take PDE and Graph Theory. I know Diff Eq and PDE are very useful so I'll definitely take them, but Graph Theory is just interesting and perhaps not so useful. Complex Variables is frequently mentioned as being good preparation... Swap graph theory for something else? Take it, and take more math? Possible upper level math choices: Complex Variables, Numerical Analysis, Graph Theory, Intro to Topology, Real Analysis 1, Intro to Mathematical Logic (pure math, symbolic logic, etc.).