Here are my notes and solutions to accompany the book *A First Book of Quantum Field Theory* (Second Edition) by Amitabha Lahiri & P. B. Pal. As always, no guarantees that my solutions are actually correct.

Errata for the book can be found here.

**Chapter 1: Preliminaries**

1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8

**Chapter 2: Classical Field Theory**

2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 2.10, 2.11

**Chapter 3: Quantization of Scalar Fields**

3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 3.10

**Chapter 4: Quantization of Dirac Fields**

Dirac equation: nonuniqueness of solutions

Dirac equation: angular momentum

Energy projection operators in the Dirac equation

Dirac creation and annihilation operators as Fourier transforms

4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10, 4.11, 4.12, 4.13, 4.14, 4.15, 4.16, 4.17, 4.18, 4.19, 4.20, 4.21, 4.22, 4.23, 4.24, 4.25, 4.26, 4.27, 4.28, 4.29, 4.30

**Chapter 5: The S-matrix expansion**

Evolution operator

S-matrix

Wick's theorem - no equal time commutators

5.1, 5.2, 5.3, 5.4

**Chapter 6: From Wick expansion to Feynman diagrams**

6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7

**Chapter 7: Cross sections and decay rates**

Decay rates

Muon decay - Feynman amplitude

7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9

**Chapter 8: Quantization of the electromagnetic field**

8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7

**Chapter 9: Quantum electrodynamics**

9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9

**Chapter 10: P, T, C and their combinations**

10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8