QUANTUM FIELD THEORY Notes taken from a course of R. E. Borcherds, Fall 2001, Berkeley Richard E. Borcherds, Mathematics department, Evans Hall, UC Berkeley, CA 94720, U.S.A. e–mail:
[email protected] home page: www.math.berkeley.edu/~reb Alex Barnard, Mathematics department, Evans Hall, UC Berkeley, CA 94720, U.S.A. e–mail:
[email protected] home page: www.math.berkeley.edu/~barnard Contents 1 Introduction 4 1.1 Life Cycle of a Theoretical Physicist . ....... 4 1.2 Historical Survey of the Standard Model . ....... 5 1.3 SomeProblemswithNeutrinos . ... 9 1.4 Elementary Particles in the Standard Model . ........ 10 2 Lagrangians 11 arXiv:math-ph/0204014v1 8 Apr 2002 2.1 WhatisaLagrangian?.............................. 11 2.2 Examples ...................................... 11 2.3 The General Euler–Lagrange Equation . ...... 13 3 Symmetries and Currents 14 3.1 ObviousSymmetries ............................... 14 3.2 Not–So–ObviousSymmetries . 16 3.3 TheElectromagneticField. 17 1 3.4 Converting Classical Field Theory to Homological Algebra........... 19 4 Feynman Path Integrals 21 4.1 Finite Dimensional Integrals . ...... 21 4.2 TheFreeFieldCase ................................ 22 4.3 Free Field Green’s Functions . 23 4.4 TheNon-FreeCase................................. 24 5 0-Dimensional QFT 25 5.1 BorelSummation.................................. 28 5.2 OtherGraphSums................................. 28 5.3 TheClassicalField............................... 29 5.4 TheEffectiveAction ............................... 31 6 Distributions and Propagators 35 6.1 EuclideanPropagators . 36 6.2 LorentzianPropagators . 38 6.3 Wavefronts and Distribution Products . ....... 40 7 Higher Dimensional QFT 44 7.1 AnExample..................................... 44 7.2 Renormalisation Prescriptions . ....... 45 7.3 FiniteRenormalisations . 47 7.4 A Group Structure on Finite Renormalisations . ........ 50 7.5 More Conditions on Renormalisation Prescriptions .