Well, I am a second year astrophysics student in the UK. However, I want to go for a PHD in theoretical physics after my graduation. So I believe I have to take more maths modules as much as possible. I have taken mathematical techniques 1 and 2 which cover up to vector calculus, differential equations, Fourier series and bit complex analysis (up to contour integration). I can't take real analysis module formally as I didn't take linear algebra in my first year (Initially I thought of go for astrophysics). But I am gonna just listen to the lectures. What do you recommend the best for me? What topics should I learn in particular before lectures begin? Cheers!