Hi,(adsbygoogle = window.adsbygoogle || []).push({});

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.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Boundary conditions for open and closed strings

Can you offer guidance or do you also need help?

Draft saved
Draft deleted

**Physics Forums | Science Articles, Homework Help, Discussion**