PHY 6648 "Quantum Field Theory I"
Class Diary for Fall 2012

 

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Date Notes
Wednesday 8/22 Introductions, course policies. Inspirational reading (handout): F. Wilczek, "Quantum Field Theory", Rev. Mod. Phys. 71, S85 (1999), also available as hep-th/9803075. Alternative inspirational reading: Permanent Jobs Elusive for Recent Physics PhDs. Data sources: Physics Doctorates Initial Employment, Physics Doctorates One Year Later
Friday 8/24 Review of Lagrangian and Hamiltonian formulation of particle dynamics. Generalization to classical field theory. Derivation of the Euler-Lagrange equations. Hamiltonian field theory.
Monday 8/27 Example: Klein-Gordon action. Klein-Gordon equation. Hamiltonian description. Begin derivation of Noether's theorem.
Wednesday 8/29 Finish derivation of Noether's theorem.
Friday 8/31 Symmetries and conservation laws. Translations, rotations, internal U(1) symmetry.
Monday 9/3 Labor Day - no class.
Wednesday 9/5 Second quantization. Quantization conditions. Review of QM of simple harmonic oscillator. Ladder operators and their commutation relations.
Friday 9/7 Consistency check of the quantization conditions. Derivation of the Hamiltonian in terms of the ladder operators. Eigenstates of the Hamiltonian and the momentum operator. Particle interpretation.
Monday 9/10 Statistics. Lorentz invariant measure. Comparison of conventions. Heisenberg representation.
Wednesday 9/12 Causality. Time ordered product. Feynman propagator.
Friday 9/14 Derivation of the Feynman propagator for a scalar field.
Monday 9/17 Lorentz invariance of the Lagrangian and the field equations for the scalar and electromagnetic field. (Chapter 3.1). Introduction to groups. Examples of finite (discrete) groups.
Wednesday 9/19 Examples of continuous groups: O(2), SO(2), U(1), O(3) and SO(3). The importance of generators.
Friday 9/21 Algebra of the generators. The group SU(2). Representation of spatial rotations in terms of SU(2). The Lorentz group: generators of rotations and their algebra.
Monday 9/24 The Lorentz group: generators of boosts and their algebra. The SU(2)xSU(2) structure of the Lorentz group. Algebra of the A and B generators. (1/2,0) and (0,1/2) Weyl spinors and their transformation properties. Weyl equations.
Wednesday 9/26 Helicity. Building Lorentz-invariant objects out of Weyl spinors. Reality properties. Majorana spinors. The Dirac Lagrangian and its symmetries (see Problem 3 from HW Set No. 5).
Friday 9/28 Free-particle solutions of the Dirac equation. (Chapter 3.3) Dirac spinors and the Klein-Gordon equation. Plane-wave solutions. u and v spinors: general form.
Monday 10/1 Normalization conditions for u and v spinors. Spin sums (end of Section 3.3).
Wednesday 10/3 Quantization of the Dirac field (Section 3.5).
Friday 10/5 The spin of a Dirac particle. Angular momentum from Noether's theorem. Angular momentum operator and its eigenvalues.
Monday 10/8 Interaction Lagrangians. Requirements. Dimensional analysis. Examples: phi-fourth, Yukawa, QED. Gauge invariance. Covariant derivatives.
Wednesday 10/10 Introduction to CompHEP. CompHEP tutorial.
Friday 10/12 Section 4.2: Perturbation expansion of correlation functions: Free scalar field in the Schrodinger and Heisenberg picture, interacting scalar field. Time evolution operator U(t,t0). The differential equation for U and its solution. Time-ordering and exponentiating the solution. Eq. (4.31).
Monday 10/15 Section 4.3: Wick's theorem. Normal ordering versus time ordering. Contractions. Simple Feynman diagrams. Feynman diagrams (section 4.4). 2-point correlation function including interactions. Combinatorics of the first-order term. Symmetry factors.
Wednesday 10/17 Feynman rules for phi-fourth theory. Example of a third-order term. Feynman rules in momentum space. Connected versus disconnected diagrams. Examples of factorizing the vacuum bubbles: a 2-point function, a 4-point function. Feynman rules in momentum space: momentum conservation at each vertex, factors at external points.
Friday 10/19 Cross-sections (section 4.5). Definitions. S-matrix. T-matrix. The general formula for 2 to N scattering. Decay rates. 2-body phase space. Formula for 2 to 2 scattering in the CM frame. Simplified version for the case of equal masses.
Monday 10/22 Calculation of T-matrix elements in terms of Feynman diagrams. Examples of disconnected diagrams. Amputated diagrams. Contractions with external states. Example: the first order term in the 2 to 2 amplitude in phi-fourth theory. 2 to 2 cross-section in phi-fourth theory. An improved version of the Feynman rules for phi-fourth theory.
Wednesday 10/24 Feynman rules. Propagators for spin 0, 1/2, 1 and 2 particles.
Friday 10/26 Vertices. External fermions. External photons. Minus sign rules for fermions. Elementary processes of QED. Begin calculation of the matrix element squared for electron-positron annihilation into muon pairs.
Monday 10/29 Finish the calculation of the cross-section for e+ e- into mu+ mu-. Spin sums and averaging. Trace technology of gamma matrices. The differential cross-section in terms of the scattering angle.
Wednesday 10/31 Mandelstam variables. Crossing symmetry. Electron-muon scattering.
Friday 11/2 Compton scattering. Spin sums for photons. Organising the calculation. Evaluation of traces.
Monday 11/5 Finish the calculation of Compton scattering.
Wednesday 11/7 Crossing symmetry: e+ e- annihilation into photons. High energy limit. Discussion of singularities in the s,t and u channels. Monte Carlo integration methods and their application in particle physics.
Friday 11/9 Homecoming - no class.
Monday 11/12 Veteran's day - no class.
Wednesday 11/14 Types of radiative corrections. Ultraviolet and infrared divergences. Quantum computation of soft bremsstrahlung.
Friday 11/16 Field trip: SESAPS meeting and UF-FSU particle physics workshop.
Monday 11/19 Section 6.2: The electron vertex function: formal structure. Consequences from Lorentz and gauge invariance. Form factors. Electric charge and magnetic moment of the electron.
Wednesday 11/21 Thanksgiving holiday - no class.
Friday 11/23 Thanksgiving holiday - no class.
Monday 11/26 Section 6.3: The electron vertex function: evaluation. Feynman parameters. Manipulation of the denominator.
Wednesday 11/28 Evaluation of loop integrals. Teaching evaluations.
Friday 11/30 Pauli-Villars regularization. Finish the calculation of the electron vertex function.
Monday 12/3 Section 6.4 The electron vertex function: IR cancellation.
Wednesday 12/5 Last lecture: distribute final exam. Overview of past homework problems.