General Information

Introduction to relativistic quantum field theory for applications in particle physics. Topics include quantization of Klein-Gordon, Dirac and gauge fields, Lorentz invariance in quantum theory, perturbation theory, Feynman diagrams, calculation of decay rates and cross sections, and an introduction to radiative corrections, renormalization and effective field theories. At the level of Quantum Field Theory and the Standard Model by Schwartz.

Prerequisites

PHYS 6572, and PHYS 6561, or equivalent experience. (One of these courses may be taken concurrently.) Background in particle physics at the level of PHYS 4444 is desirable.

Topics Covered

  • Free spin-0 fields (Canonical quantization, causality, symmetries)
  • Interacting spin-0 fields (S-matrix, Feynman rules, unitarity, renormalization, spectral decomposition)
  • Spin-1/2 fields (Lorentz and Poincar ́e groups, Weyl fermions, Dirac fermions, quanti- zation and renormalization of spinors)
  • If we have time we will do path integrals/and or basics of scattering amplitudes

Workload

  • 10-15hrs/week, 13 problem sets, one take home final [FA23]
  • 10-15 hours/week, 1 take-home final [FA24]
  • The workload for QFT 1 is very very high; The year I took it there were 12 homeworks one in-person final, which is different from previous years. The psets are very demanding, with the average of them taking around ~15-20 hours, though some are easier and some are much harder. All in all, this class is very hard! [FA25]
  • Pset every week, rather difficult, probably 10 hours per week outside of class. [FA25]

General Advice

  • This class is hard! [FA24]
  • While challenging, take this class as early as possible if you’re into theory. Try to get a very solid understanding of quantum mechanics. [FA24]
  • I would truthfully recommend not taking this class in an already busy semester; QFT is fabled as a difficult class, and I can firsthand say that this is indeed the case. There were often weeks wherein I hadn’t submitted the homework by the due date, and I ended up submitting it days, and sometimes even weeks, late. Towards the end of the semester, it got to the point where I was almost scared to start the homework, I would continuously put it off and do other homework, just because I knew it was going to be that bad. Though, this is all to say that while QFT is a very difficult class, it is still one of my favorite, and very may well be my 2nd favorite, physics class I have taken at Cornell. [FA25]
  • Make sure you have the time and energy to dedicate to this class, and form a homework group. [FA25]

Testimonials

  • The material is challenging, but very rewarding as all of high energy theory is locked behind the iron door of QFT. The material demands a strong background in quantum mechanics, although you do not have to take Cornell’s 6572 to do well. It is also a lot of work. [FA23]
  • While challenging, take this class as early as possible if you’re into theory. Try to get a very solid understanding of quantum mechanics. [FA24]
  • Despite the intense workload, I really enjoyed this class! At times, the lectures could go on for a little long, and sometimes I didn’t really understand what was being said in lecture, but I still enjoyed the class nevertheless. We covered all of scalar field theory, and towards the latter 1/3rd of the semester, we covered fermions. That included a bit of group theory, and the Feynman rules for Dirac fermions in general. [FA25]
  • This is an important class for theorists, and it is good to take it as an undergrad if you are interested in theory, but you will almost certainly have to take it again. I would not recommend taking this class unless you are certain you have the time and motivation to dedicate to it. It is infamously difficult to follow, fast-paced, and dense. [FA25]

Resources

Past Offerings

Semester Professor Median Grade Course Page
Fall 2023 Csaba Csaki N/A PHYS7651_FA23.pdf
Fall 2024 Csaba Csaki N/A PHYS7651_FA24.pdf
Fall 2025 Csaba Csaki N/A PHYS7651_FA25.pdf