Hey guys, So I am a physics and math major so far I am took Calculus I,II,III linear algebra and statistics I did really good in them almost acing all of them and aced vector calculus. I am taking complex analysis and introduction to probability in fall. I have holiday in the winter break for about 1 month and I want to self study some high level material, so what would you suggest studying ? I am planning to go into theortical physics PHD besides I really like math and started to like it even more than physics,so I want to improve myself even more than university so I need some suggestions. I don't know if this is the right section to post this but it seems like it.