Hi Everyone, I don't know what kind of my message is so I post it here as it is matter of physics. In fact, I am a UG Students who had just finished my First year. I am so impressed by the "thought experiment" , the "theoretical approach to physics" and "The expression of natural phenomenon in Mathematics" I really want to get into the field of theoretical physics in future and I don't know what can I actually do for preparation. I understand that Good mathematical background is essential in theoretical physics. However, what shall I prepare in my UG year? To me, mathematics is simply divided into Calculus, Geometry, Algebra. I don't have a clear mind in the division of mathematics, as a result, I don't know where to start. If you are now in the theoretical field, PostGraduate or Master or Doctor. What field of Mathematics do you think is the most important? for referrence, I have took three math course in my first year and got satisfactory result. 1. linear algebra 2. multivaribale calculus 3. Differential equation Thank You!