**Class #1 (Jan. 17) Reading Questions - Particle
Physics, Sec. 4; Handout pgs. 59-66**

1. The Dirac
equation, the relativistic wave equation for spin 1/2 particles, involves a
4-component wave-function (usually represented as a column vector). What is the physical interpretation of
the four components?

2. According to the handout how
do you distinguish a particle from an antiparticle in a Feynman diagram? Based
on the handout, what is wrong with the QED
diagrams shown in Figs. 4.3 and 4.4 of our text. [By the way, correctly drawn Feynman
diagrams provide a visual representation of the Feynman-Stuckelberg
interpretation of Dirac's "sea of negative energy particles".]

3. What is a "virtual" particle? How
do you distinguish real particles from "virtual" particles in a
Feynman diagram?

4. Why does one typically not bother
calculating QED Feynman diagrams with more than say 4 vertices?

5. What is meant by renormalization? People often talk about the "bare
electron mass". What do you
think this means?

**Your Question:** Please give a well formulated question
that you have regarding the material covered in this reading assignment.