I enjoy reading your QM book; as usual, it is very well written!

Here is a quick question: In chapter 8, you say that P(reflection)=|A|^2 and P(transmission)=|B|^2. Later, when I plug E=U into your equations for the step potential (Section 8.1.1/2), I get A=1 and B=2. Something is not normalized properly… What are the correct probabilities for reflection & transmission in the case E=U? ]]>

The same question is for page 299 where for the formula |E2>=a+|E1> I’d rather expect sqrt(2)*|E2> = a+|E1>

I see some consistency here but fail to understand if it’s a problem or not. ]]>

I have problems understanding the following:

In chapter four I consider that the global shift (Eq. (4.49)) of the scalar field should be a symmetry of the Klein-Gordon Lagrangian ((Eq. (5.2)), that is, the shift phi—>phi ‘=phi-ie should leave the Klein-Gordon Lagrangian unchanged, but a direct replacement in the Lagrangian does not show this symmetry explicitly, i.e., dL is nonzero. I ask this question because this symmetry is used in Chapter 8 (Eq. 8.2 ) in the context of scalar fields.

]]>Thanks for your feedback. There is indeed a typo in the gamma matrices. The correct matrices read

$$ \gamma^1 = \begin{pmatrix} 0 & 0 &0 &1 \\ 0 & 0 &1 &0 \\ 0 & -1 &0 &0 \\ -1 & 0 &0 &0 \end{pmatrix} , \gamma^2 = \begin{pmatrix} 0 & 0 &0 &-i \\ 0 & 0 &i &0 \\ 0 & i &0 &0 \\ -i & 0 &0 &0 \end{pmatrix}\, $$

$$ \gamma^3 = \begin{pmatrix} 0 & 0 &1 &0 \\ 0 & 0 &0 &-1 \\ -1 & 0 &0 &0 \\ 0 & 1 &0 &0 \end{pmatrix}$$

Best,

Jakob

I’ve got a question about the start of section 5.2: your gamma matrices don’t seem to satisfy the Clifford algebra. Using {mu, nu} = {0, 0} works out fine in your example, but for {1,1} and {2,2} the sign seems to be incorrect, i.e., g1*g1 and g2*g2 both give a positive identity matrix instead of negative, while {3,3} does seem to work correctly. Also several of the “off diagonal” terms don’t work out to a zero matrix.

Thanks again for a great book!

]]>there is just one electron field and all electrons are understood as excitations of this electron field.

]]>I just began reading your book.

Could you possibly clarify a confusion for me.

You wrote on page 24, “an elementary excitation of the electron field is what we call the electron.”.

What bothers me is this: Say, an electron in orbit around an atom gets excited. This means the excited electron was part of the electron field.

Is this electron field local to that atom or non-local to all possible existing electrons everywhere?