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A Why are open strings vectors or scalars, or massive?

  1. Jan 3, 2017 #1
    In string theory, if we have NN BCs along ##X^i, i = 1, \ldots, n-1##
    and DD BCs along ##X^a, a = n, \ldots, 25## then you get, from ##\alpha^{i,a}_{-1}|0,p\rangle ##, ##n## massless vectors and ##24-n## massless scalars. I understand that for the first excited level, ##M^2=0## and so we have no mass, but what suggests that these are scalars or vectors? In the case where we have two branes separated by a distance ##\delta##, with find ##M^2\propto\delta^2## which, in addition to the vector/scalar nature of the excitations, I don't understand.
     
  2. jcsd
  3. Jan 3, 2017 #2

    haushofer

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    Their tensorial nature is determined by the index of the creation operator, no?
     
  4. Jan 4, 2017 #3
    I'm not sure how that would be the case though; the indices on the creation operator are ##i## (or ##a##) and ##-1##. The lower index is the state number (i.e. ##\alpha_{-1}## creates a one particle state) and the upper indicates indicate whether the BCs are NN or DD.
     
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