Effective field theory

Lectures: 2 sessions / week, 1.5 hours / session

Quantum Field Theory II (8.324)

I will assume you have seen the following subjects: abelian and nonabelian gauge theories, constructing Lagrangians, renormalization, dimensional regularization, and the calculation of observables like cross sections (LSZ).

Quantum Field Theory III (8.325) or an equivalent field theory course on the standard model. This is recommended, but not required. If you have taken 8.325 then you will likely get more out of taking 8.851. If you have not taken 8.325, then the course will likely require extra work on your part, particularly if you have not studied the renormalization group. I intend to give a brief review of ideas about the renormalization group that are needed for 8.851. If you have not seen the renormalization group, or the beta-function of QCD, then you will need to do additional assigned reading.

Effective field theory is a fundamental framework to describe physical systems with quantum field theory. Part I of this course covers common tools used in effective theories: identifying degrees of freedom and symmetries; power counting expansions (dimensional and otherwise); field redefinitions; bottom-up and top-down effective theories; fine-tuned effective theories; matching and Wilson coefficients; reparameterization invariance; and advanced renormalization group techniques. Main examples are taken from particle and nuclear physics. Part II of this course is an in depth study of the Soft-Collinear Effective Theory (SCET), an effective theory for hard interactions in collider physics.

There is no required textbook. Some of the reading will be taken from the following texts. If you want to buy a book, I suggest Heavy Quark Physics, but note that it will only be useful for < 20% of the material.

My lecture notes plus assigned readings will serve as your main sources.

There will be no tests or final exam. The class will be based on homework, and one presentation on a topic of your choosing. For the homework, there will be 5 problem sets. You are expected to discuss the homework with other people in the class. The write-up must be your own work.

I will create solutions for most problems. In some cases I might use the best and neatest solution turned in by the class for a particular problem. If your solution is chosen, then by default it will remain anonymous, but you are free to override this default by telling me

Having your solution chosen has no bearing on grades.

Finally, I would like each of you to have the opportunity to explore an effective field theory subject on your own and give a short presentation to teach it to the rest of the class. See the projects section for more details and a list of possible topics, including references to start you off.

Your grade will be based on 5 problem sets and an individual presentation.

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