phy2403

Final first draft of complete notes for UofT PHY2403, QFT I .

December 27, 2018 phy2403 No comments , ,

I’ve now uploaded a new version of my class notes for PHY2403, the UofT Quantum Field Theory I course, taught this year by Prof. Erich Poppitz.

This update adds notes for all remaining lectures (up to and including lecture 23.)  I’ve made a pass with a spellchecker to correct some of the aggregious spelling erorss, and also redrawn three figures, replacing photos, which cuts the size in half!

I’ve posted the redacted version (316 pages).  The full version, with my problem set solutions (including errors) is 409 pages.

Feel free to contact me for the complete version (i.e. including my problem set solutions, with errors) of any of these notes, provided you are not asking because you are taking or planning to take this course.

Contents:

  • Preface
  • Contents
  • List of Figures
  • 1 Fields, units, and scales.
  • 1.1 What is a field?
  • 1.2 Scales.
  • 1.2.1 Bohr radius.
  • 1.2.2 Compton wavelength.
  • 1.2.3 Relations.
  • 1.3 Natural units.
  • 1.4 Gravity.
  • 1.5 Cross section.
  • 1.6 Problems.
  • 2 Lorentz transformations.
  • 2.1 Lorentz transformations.
  • 2.2 Determinant of Lorentz transformations.
  • 2.3 Problems.
  • 3 Classical field theory.
  • 3.1 Field theory.
  • 3.2 Actions.
  • 3.3 Principles determining the form of the action.
  • 3.4 Principles (cont.)
  • 3.4.1 d = 2.
  • 3.4.2 d = 3.
  • 3.4.3 d = 4.
  • 3.4.4 d = 5.
  • 3.5 Least action principle.
  • 3.6 Problems.
  • 4 Canonical quantization, Klein-Gordon equation, SHOs, momentum space representation, raising and lowering operators.
  • 4.1 Canonical quantization.
  • 4.2 Canonical quantization (cont.)
  • 4.3 Momentum space representation.
  • 4.4 Quantization of Field Theory.
  • 4.5 Free Hamiltonian.
  • 4.6 QM SHO review.
  • 4.7 Discussion.
  • 4.8 Problems.
  • 5 Symmetries.
  • 5.1 Switching gears: Symmetries.
  • 5.2 Symmetries.
  • 5.3 Spacetime translation.
  • 5.4 1st Noether theorem.
  • 5.5 Unitary operators.
  • 5.6 Continuous symmetries.
  • 5.7 Classical scalar theory.
  • 5.8 Last time.
  • 5.9 Examples of symmetries.
  • 5.10 Scale invariance.
  • 5.11 Lorentz invariance.
  • 5.12 Problems.
  • 6 Lorentz boosts, generators, Lorentz invariance, microcausality.
  • 6.1 Lorentz transform symmetries.
  • 6.2 Transformation of momentum states.
  • 6.3 Relativistic normalization.
  • 6.4 Spacelike surfaces.
  • 6.5 Condition on microcausality.
  • 7 External sources.
  • 7.1 Harmonic oscillator.
  • 7.2 Field theory (where we are going).
  • 7.3 Green’s functions for the forced Klein-Gordon equation.
  • 7.4 Pole shifting.
  • 7.5 Matrix element representation of the Wightman function.
  • 7.6 Retarded Green’s function.
  • 7.7 Review: “particle creation problem”.
  • 7.8 Digression: coherent states.
  • 7.9 Problems.
  • 8 Perturbation theory.
  • 8.1 Feynman’s Green’s function.
  • 8.2 Interacting field theory: perturbation theory in QFT.
  • 8.3 Perturbation theory, interaction representation and Dyson formula.
  • 8.4 Next time.
  • 8.5 Review.
  • 8.6 Perturbation.
  • 8.7 Review.
  • 8.8 Unpacking it.
  • 8.9 Calculating perturbation.
  • 8.10 Wick contractions.
  • 8.11 Simplest Feynman diagrams.
  • 8.12 Phi fourth interaction.
  • 8.13 Tree level diagrams.
  • 8.14 Problems.
  • 9 Scattering and decay.
  • 9.1 Additional resources.
  • 9.2 Definitions and motivation.
  • 9.3 Calculating interactions.
  • 9.4 Example diagrams.
  • 9.5 The recipe.
  • 9.6 Back to our scalar theory.
  • 9.7 Review: S-matrix.
  • 9.8 Scattering in a scalar theory.
  • 9.9 Decay rates.
  • 9.10 Cross section.
  • 9.11 More on cross section.
  • 9.12 d(LIPS)_2.
  • 9.13 Problems.
  • 10 Fermions, and spinors.
  • 10.1 Fermions: R3 rotations.
  • 10.2 Lorentz group.
  • 10.3 Weyl spinors.
  • 10.4 Lorentz symmetry.
  • 10.5 Dirac matrices.
  • 10.6 Dirac Lagrangian.
  • 10.7 Review.
  • 10.8 Dirac equation.
  • 10.9 Helicity.
  • 10.10 Next time.
  • 10.11 Review.
  • 10.12 Normalization.
  • 10.13 Other solution.
  • 10.14 Lagrangian.
  • 10.15 General solution and Hamiltonian.
  • 10.16 Review.
  • 10.17 Hamiltonian action on single particle states.
  • 10.18 Spacetime translation symmetries.
  • 10.19 Rotation symmetries: angular momentum operator.
  • 10.20 U(1)_V symmetry: charge!
  • 10.21 U(1)_A symmetry: what was the charge for this one called?
  • 10.22 CPT symmetries.
  • 10.23 Review.
  • 10.24 Photon.
  • 10.25 Propagator.
  • 10.26 Feynman rules.
  • 10.27 Example: muon pair production
  • 10.28 Measurement of intermediate quark scattering processes.
  • 10.29 Problems.
  • A Useful formulas and review.
  • A.1 Review of old material.
  • A.2 Useful results from new material.
  • B Momentum of scalar field.
  • B.1 Expansion of the field momentum.
  • B.2 Conservation of the field momentum.
  • C Reflection using Pauli matrices.
  • D Explicit expansion of the Dirac u,v spinors.
  • D.1 Compact representation of
  • E Mathematica notebooks
  • Bibliography

my course evaluation comments for PHY2403 — Quantum Field Theory I.

November 20, 2018 phy2403 No comments , , ,

Here are my evaluation comments for QFT I. The university provides an anonymous facility to submit course feedback, but since I have no conflicts that require anonymization, I’m posting my commentary (and rationale for some of my list selections) publicly.

Q) Please comment on the overall quality of the instruction in this course.

Professor Poppitz’s knowledge of the subject matter is impressive and thorough. I expect that this is a particularly difficult course to teach and think that he has done an admirable job trying to work through the maximum amount of material in the limited time available in this course.

It is challenging but fun game (albeit a slightly masochistic one) to keep up with Prof Poppitz’s blistering pace through the course material. Poppitz often says “Phew!!” at the end of the race to complete a long derivation in the allotted time, and I’ll be saying the same thing at the end of this course.

The barrage of abstract material covered in a lecture is often sufficient to leave me with a headache, and it takes a few hours to recover from each class. It takes a few more hours after that to digest the material at a human pace.

This course would strongly benefit from video recorded lectures that some of the more educationally progressive academic institutions currently provide (i.e. MIT’s OCW and Yale’s “Open Yale” courses). With the exception of the UofT SciNet group (phy1610 — Scientific computing for Physicists), I’m not aware of any UofT physics courses that provide such recordings. For phy2403, video recordings would be particularly valuable, as it would allow the student to “pause” the Professor and work through the material presented at an individually suitable pace.

Q) Please comment on any assistance that was available to support your learning in the course.

Prof Poppitz was available continually on the course forum, after class briefly, and in weekly office hours. I received a great deal of helpful assistance from him during the course.

Q) Compared to other courses, the workload for this course was…

I picked Heavy (not Very Heavy), but I’m not in a good position to evaluate since I’m only taking one course.

Q) I would recommend this course to other students.

I picked Mostly (not Strongly). I wouldn’t recommend this course to anybody who was not adequately prepared. I’m not sure that I was. It is a very tough course. I was continually impressed with the other students in the class. I’ve worked slowly for years to gradually build up the background required to take this course, and all the rest of these younglings are downing the material with seeming ease. There are a lot of exceptionally smart students enrolled on this course.

New aggregate collection of class notes for phy2403: up to lecture 17.

November 14, 2018 phy2403 No comments

I’ve now uploaded a new version of my class notes for PHY2403, the UofT Quantum Field Theory I course, taught this year by Prof. Erich Poppitz.

This version includes the following chapters, roughly one per lecture, plus some extras

  • Introduction
  • Units, scales, and Lorentz transformations.
  • Lorentz transformations and a scalar action.
  • Scalar action, least action principle, Euler-Lagrange equations for a field, canonical quantization.
  • Klein-Gordon equation, SHOs, momentum space representation, raising and lowering operators.
  • Canonical quantization, Simple Harmonic Oscillators, Symmetries
  • Symmetries, translation currents, energy momentum tensor.
  • 1st Noether theorem, spacetime translation current, energy momentum tensor, dilatation current.
  • Unbroken and spontaneously broken symmetries, Higgs Lagrangian, scale invariance, Lorentz invariance, angular momentum quantization
  • Lorentz boosts, generator of spacetime translation, Lorentz invariant field representation.
  • Microcausality, Lorentz invariant measure, retarded time SHO Green’s function.
  • Klein-Gordon Green’s function, Feynman propagator path deformation, Wightman function, Retarded Green’s function.
  • Forced Klein-Gordon equation, coherent states, number density, time ordered product, perturbation theory, Heisenberg picture, interaction picture, Dyson’s formula
  • Time evolution, Hamiltonian pertubation, ground state
  • Perturbation ground state, time evolution operator, time ordered product, interaction
  • Differential cross section, scattering, pair production, transition amplitude, decay rate, S-matrix, connected and amputated diagrams, vacuum fluctuation, symmetry coefficient
  • Scattering, decay, cross sections in a scalar theory.
  • Problem Set 1.
  • Problem Set 2.
  • Independent study problems
  • Useful formulas and review.
  • Momentum of scalar field.
  • Index
  • Bibliography

Problem set 1-2 solutions are redacted.  If you aren’t a UofT student taking PHY2403, feel free to contact me for an un-redacted copy.

New aggregate notes collection for UofT phy2403 Quantum Field Theory I

October 21, 2018 phy2403 No comments , ,

I’ve uploaded a new aggregate notes collection of my UofT phy2403 Quantum Field Theory I class notes (taught by Prof. Erich Poppitz), which now includes up to Wed Oct 17th’s lecture 11 (but doesn’t have my problem set I solution)

  • 1 Introduction
  • 1.1 What is a field?
  • 1.2 Scales.
  • 1.2.1 Bohr radius
  • 1.2.2 Compton wavelength.
  • 1.2.3 Relations.
  • 2 Units, scales, and Lorentz transformations.
  • 2.1 Natural units.
  • 2.2 Gravity.
  • 2.3 Cross section.
  • 2.4 Lorentz transformations.
  • 3 Lorentz transformations and a scalar action.
  • 3.1 Determinant of Lorentz transformations.
  • 3.2 Field theory.
  • 3.3 Actions.
  • 3.4 Problems.
  • 4 Scalar action, least action principle, Euler-Lagrange equations for a field, canonical quantization.
  • 4.1 Principles cont.
  • 4.2 d = 2 .
  • 4.3 d = 3 .
  • 4.4 d = 4 .
  • 4.5 d = 5 .
  • 4.6 Least action principle (classical field theory)
  • 4.7 Canonical quantization.
  • 5 Klein-Gordon equation, SHOs, momentum space representation, raising and lowering operators.
  • 5.1 Canonical quantization.
  • 5.2 Momentum space representation.
  • 6 Canonical quantization, Simple Harmonic Oscillators, Symmetries
  • 6.1 Quantization of Field Theory.
  • 6.2 Free Hamiltonian.
  • 6.3 QM SHO review.
  • 6.4 Discussion.
  • 6.5 Switching gears: Symmetries.
  • 7 Symmetries, translation currents, energy momentum tensor.
  • 7.1 Symmetries.
  • 7.2 Spacetime translation.
  • 8 1st Noether theorem, spacetime translation current, energy momentum tensor, dilatation current.
  • 8.1 1st Noether theorem.
  • 8.2 Unitary operators.
  • 8.3 Continuous symmetries.
  • 8.4 Classical scalar theory.
  • 9 Unbroken and spontaneously broken symmetries, Higgs Lagrangian, scale invariance, Lorentz invariance, angular momentum quantization
  • 9.1 Last time.
  • 9.2 Examples of symmetries.
  • 9.3 Scale invariance.
  • 9.4 Lorentz invariance.
  • 10 Lorentz boosts, generator of spacetime translation, Lorentz invariant field representation.
  • 10.1 Lorentz transform symmetries.
  • 10.2 Transformation of momentum states.
  • 11 Microcausality, Lorentz invariant measure, retarded time SHO Green’s function.
  • 11.1 Relativistic normalization.
  • 11.2 Spacelike surfaces.
  • 11.3 Condition on microcausality.
  • 11.4 Harmonic oscillator.
  • 11.5 Field theory (where we are going).
  • 12 Independent study problems
  • Appendices
  • A Useful formulas and review
  • Index
  • Bibliography