## Errata found in “String Theory Demystified”

We have by now a bunch of them (see comments below). Did you find one? Then leave a replay with a description. Authorship will be acknowledged in the final errata sheets.

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### 16 Responses to Errata found in “String Theory Demystified”

1. Ψε says:

On page 10, equation (1.10), The “=” sign should be a \geq.

2. Ψε says:

Also, McMohan often uses gauge group and symmetry group interchangably, which isn’t correct.

• Ψε says:

Usually, he should be saying “gauge symmetry”.

3. Ψε says:

In some equations, e.g. 9.29, 9.12, 9.15, etc. he uses natural units, but in others, e.g. 8.36, 8.37, etc. he explicitly writes down alpha’, c_0 and other such constants. So, if you ever see an alpha’ or c_0, then just set them equal to 1 in your head so that the other equations are consistent with it.

• Ψε says:

List of equations in which natural units are used in Chapter 1: 1.4, 1.11.

• Ψε says:

List of equations in which natural units are used in Chapter 2: 2.8, The equations after 2.25 but before 2.26, 2.26, 2.23, 2.44, 2.50, 2.51, all the equations with $\dot X$ in it. The equations after the equation right after 2.52, i.e. those under “Now, looking at Eqs. (2.48) and (2.49) we see that”, and the equation after the equation under “Summing these as in Eq. (2.47) and setting σ = 0,” The Equvwation before 2.53, 2.53, 2.55, 2.56, 2.59 (and the equation before it),

In equation 2.8, and many other equations, there are no differentials in the integral, and the integral wouldn’t be well defined. There should be a “dσ dτ”.

Related problem: He makes no indication that the Regge Slope Parameter alpha’ is the string length squared.

• Ψε says:

Oh and 2.19, also! .

• List of equations in which natural units are used in Chapter 3: None, probably because he starts using the $\sigma^0$ notation now.

List of equations in which natural units are used in Chapter 4:

All the commutation relations which means:
– The set of equations that come after “In ordinary quantum mechanics
the position and momentum coordinates satisfy” (at this point, he does admit that he has set $\hbar=1$, so I’m not sure if this can be considered to be a sort of “errata”?)
– The set of equations after that.
– The equation before 4.1.
– 4.1
– The set of equations that come after 4.2.
– 4.3 to 4.5
– 4.6 to 4.9
– The equation after 4.9
– Equation 4.11
– 4.14 to the equation before 4.15
– 4.16 to the equation after 4.22
– The equation after $N\vert 0\rangle=n\vert0\rangle$, which comes after the last equation mentioned in the previous point.
– The equation after that
– About Almost All the equations in the section “CLOSED STRING SPECTRUM”
– About Almost All the equations in the section “Light-Cone Quantisation”
/

• List of equations in which natural units are used in Chapter 3: None, probably because he starts using the $\sigma^0$ notation now.

List of equations in which natural units are used in Chapter 4:

All the commutation relations which means:
– The set of equations that come after “In ordinary quantum mechanics
the position and momentum coordinates satisfy” (at this point, he does admit that he has set $\hbar=1$, so I’m not sure if this can be considered to be a sort of “errata”?)
– The set of equations after that.
– The equation before 4.1.
– 4.1
– The set of equations that come after 4.2.
– 4.3 to 4.5
– 4.6 to 4.9
– The equation after 4.9
– Equation 4.11
– 4.14 to the equation before 4.15
– 4.16 to the equation after 4.22
– The equation after $N\vert 0\rangle=n\vert0\rangle$, which comes after the last equation mentioned in the previous point.
– The equation after that
– About Almost All the equations in the section “Closed String Spectrum”
– About Almost All the equations in the section “Light-Cone Quantisation”
/

• List of equations in which natural units are used in Chapter 3: None, probably because he starts using the $\sigma^0$ notation now.

List of equations in which natural units are used in Chapter 4:

All the commutation relations which means:
– The set of equations that come after “In ordinary quantum mechanics
the position and momentum coordinates satisfy” (at this point, he does admit that he has set $\hbar=1$, so I’m not sure if this can be considered to be a sort of “errata”?)
– The set of equations after that.
– The equation before 4.1.
– 4.1
– The set of equations that come after 4.2.
– 4.3 to 4.5
– 4.6 to 4.9
– The equation after 4.9
– Equation 4.11
– 4.14 to the equation before 4.15
– 4.16 to the equation after 4.22
– The equation after $N\vert 0\rangle=n\vert0\rangle$, which comes after the last equation mentioned in the previous point.
– The equation after that
– About Almost All the equations in the section “CLOSED STRING SPECTRUM”
– About Almost All the equations in the section “Light-Cone Quantisation”

• List of equations in Chapter 5 where natural units are used:
– Basically the entire chapters on Wick Rotations and Complex Co-ordinates. The preceeding chapters don’t use natural units because they are about abstract algebra (conformal algebra, specifically) in general, and not about ST, specifically.
– Equation 5.29, 5.30.

4. Ψε says:

In Section 1, under “HIGHER DIMENSIONS”, he says: “We live in a world with three spatial dimensions. In a nutshell this means that there
are three distinct directions through which movement is possible: up-down, leftright,
and forward-backward.”. Uh… He’s missing the word orthogonal before the word “directions”.

• Ψε says:

Also, in Section 1, for the problems section, the answer to question 9 should be both c and d, not just c. It’s the very reason why Type II strings aren’t realistic.

• Ψε says:

Also in the problems section (Sorry for the spam…), Question 7 is just meaningless. “Heterotic string theory has the gauge group…” “Which heterotic string theory?” is not mentioned. So the question is meaningless.

Furthermore, throughout the book, he says that “SO(32)” is the gauge group of Type HO string theory. However, it is actually Spin(32)/Z_2, to be precdise.

5. Siraj R Khan says:

On page 288 in the solutions section of chapter 7: The answer to question 5 has too many beta indices in the first term. I got an alpha in place of the beta in \partial_{beta}X^{\mu} in the first term. My result matches that of equation (7.17).

6. Siraj R Khan says:

Page 136, equation (7.13): There should be no \mu index on the LHS as \mu indices contract on RHS.