I have this, probably quite simple, problem. In the RNS superstring, when varying the action, we obtain in general a term [tex] \int d\tau [X'_{\mu}\delta X^{\mu}|_{\sigma=\pi}-X'_{\mu}\delta X^{\mu}|_{\sigma=0} + (\psi_+ \delta \psi_+ - \psi_- \delta \psi_-)|_{\sigma=\pi}-(\psi_+ \delta \psi_+ - \psi_- \delta \psi_-)|_{\sigma=0}][/tex], where the notation should be standard (as e.g. in Becker-Becker-Schwarz).(adsbygoogle = window.adsbygoogle || []).push({});

My question is the following: couldn't one also take other boundary conditions as those that one takes usually? For example, couldn't [tex]X^{\mu}[/tex] be anti-periodic (i.e. an antiperiodic closed string), or cuoldn't we take a boundary condition for the fermion in the form [tex]\delta \psi_+=\delta \psi_-=0[/tex]? Can one show that there are no solutions to such boundary conditions (because nobody does that in a textbook)?

**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 in String Theory

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