So I'm a second year undergraduate physics major, and I'm taking quantum mechanics and classical mechanics next semester. I have all the basic math requirements completed (calculus and diff eq) Currently, I'm interested in doing PhD work in particle physics/atomic physics once I graduate. And I also need more classes to take and I'm ahead of schedule for graduation, so I was wondering what classes I should take to strengthen my background in other fields relevant to what I want to study. I've talked to some of the professors on my campus briefly and they mentioned classes like complex analysis and partial differential equations. I was just wondering what would be some good classes to take in chemistry or math or CS cuz I need more hours next semester. Thanks guys!