Overview#

Template for Solution Document: https://docs.google.com/document/d/1LRtMKRAzp9Ov8_vFMkPbNbUwGrQ7v2X0Z0uHd4t0ttk/edit?usp=sharing

Our goal in this section is to understand the renormalization group. The renormalization group answers the question: How do the rules of the universe change when you look at in a coarse-grain way (i.e. you don’t have your glasses on so you can’t see all the tiny details).

Three aspects the renormalization group helps us understand:

  • Why do the rules of the universe look simple? Have you ever wondered why you can compute properties of an atom without knowing quantum chromo-dynamics. It’s because when we probe quarks, the rules of the universe are controlled by quantum chromo-dynamics. But, when we probe atoms, the rules which are relevant at this level renormalize. They are simpler.

  • A more sophisticated understanding of phases. Lots of different physics all result in the same phase; for example, there are many liquids in the world. How is it we identify all these phases as the same thing. At the microscopic level, these phases all look very different. Once we renormalize, though, looking at things through a coarse-grained view, the phases all appear to be the same.

  • A more sophisticated understanding of the critical point. Between two phases there is a critical point. If we coarse-grain that critical point we find that all critical points flow to a finite numbner of such points.

Your renormalization group assignment will consist of three pages (1 per week)

References#