1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Zwiebach Exercise 9.3b

  1. Oct 5, 2007 #1
    1. The problem statement, all variables and given/known data
    Apparently the answer is sqrt(2 alpha') *4a. But doesn't equation 9.10 imply that the 4a should just be a 1?

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Oct 5, 2007 #2
    It's kind of a coincidence that when I did that problem two years ago, that's what I wrote in the margin of my book. However it is not true. [itex]l_s[/itex] is just a unit of length like the Planck length. It is not necessarily the length of any string. It is useful as a unit of length when doing string theory as this problem shows. The answer is [itex]4\sqrt{2}a[/itex] in units of the string length.
    Last edited: Oct 5, 2007
  4. Oct 6, 2007 #3
    I see--we need to integrate differential lengths from sigma = 0 to sigma = 2 pi. Thanks.
    Last edited: Oct 6, 2007
  5. Oct 6, 2007 #4
    That's for closed strings. As this is an open string, the range is different.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Zwiebach Exercise Date
Zwiebach page 287 Nov 30, 2007
Zwiebach page 299 Nov 30, 2007
Zwiebach page 292 Nov 26, 2007
Zwiebach QC 17.4, page 404 Nov 11, 2007
Zwiebach Exercise 9.3e Oct 6, 2007