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Boundary conditions for open and closed strings

  1. Sep 17, 2014 #1

    I am a bit confused about the terminology used for the boundary conditions describing open and closed strings.

    For the open string,

    Ramond case: [itex]\psi^+(\sigma = \pi, t) = \psi^-(\sigma = \pi, t)[/itex]
    Neveu-Schwarz case: [itex]\psi^+(\sigma = \pi, t) = -\psi^-(\sigma = \pi, t)[/itex]

    Question 1: Is it correct that the "R sector" refers to the Ramond case, and the "NS sector" refers to the Neveu-Schwarz case?

    For the closed string,

    Ramond case: [itex]\psi^+(\sigma = 0) = \psi^+(\sigma = \pi)[/itex], [itex]\psi^+(\sigma = 0) = \psi^-(\sigma = \pi)[/itex]

    Neveu-Schwarz case: [itex]\psi^+(\sigma = 0) = \psi^+(\sigma = \pi)[/itex], [itex]\psi^+(\sigma = 0) = -\psi^-(\sigma = \pi)[/itex]

    Question 2: So,

    NS-NS means both [itex]\psi^+[/itex] and [itex]\psi^-[/itex] are antiperiodic
    NS-R means [itex]\psi^+[/itex] is antiperiodic and [itex]\psi^-[/itex] is periodic
    R-NS means [itex]\psi^-[/itex] is antiperiodic and [itex]\psi^+[/itex] is periodic
    R-R means [itex]\psi^+[/itex] is periodic and [itex]\psi^-[/itex] is periodic?

    I apologize for the triviality of these questions but the classification of the 4 sectors is confusing me a little...

    I'd appreciate some help.
  2. jcsd
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