Equation 14.81 in Zwiebach: Why No 2?

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Homework Help Overview

The discussion revolves around equation 14.81 from Zwiebach's text, specifically questioning the treatment of the lower indices of oscillators alpha^r and alpha^s in relation to their division by 2, as seen in a previous equation (14.77). Participants are examining the differences in their editions of the text and the implications of these differences on the equations presented.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to reconcile differences in their editions of the text regarding the indices of the oscillators. Questions are raised about whether the absence of division by 2 in equation 14.81 is a typographical error, especially in light of the commutator in equation 14.82, which does include the division.

Discussion Status

There is a consensus among some participants that the discrepancy may be a typographical error, with references made to errata provided by the author. However, there is no explicit resolution or agreement on the matter, as participants continue to explore the implications of the differences in their texts.

Contextual Notes

Participants note variations in their editions of the book, which may affect the interpretation of the equations discussed. The mention of an errata page suggests that there may be ongoing updates or corrections relevant to the discussion.

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Homework Statement


In equation 14.81, why are the lower indices of the oscillators alpha^r and alpha^s not divided by 2 like they were in equation 14.77?


Homework Equations





The Attempt at a Solution

 
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ehrenfest said:

Homework Statement


In equation 14.81, why are the lower indices of the oscillators alpha^r and alpha^s not divided by 2 like they were in equation 14.77?


Homework Equations





The Attempt at a Solution


In my edition, equation 14.81 has no alpha (it has integrals with exponentials) . But my equation 14.82 has the commutator of alpha^r and alpha^s and they have, respectively, the subscripts m/2 and n/2.
I am not sure if you have that.
 
I'm sorry. I meant 14.80. Mine has subscripts of m and n (not divided by 2) so it must be a typo. That would make much more sense since the commutator of 14.82 in my book does have subscripts that are divided by 2.
 
Last edited:
I'm pretty sure it's a typo. Here is Professor Zwiebach's errata page. It has his e-mail address where you can send him this one.

http://xserver.lns.mit.edu/~zwiebach/firstcourse.html"
 
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