GSO projection

introduction

• The GSO projection of the RNS model yields a ten-dimensional string theory, called superstring theory, which is supersymmetric in spacetime and does not contain tachyons.
• The RNS formalism has spacetime supersymmetry after projecting out half of the states using the GSO projection. However, it is not manifestly supersymmetric. Green and Schwarz, using the light-cone gauge, have given a formulation with manifest spacetime supersymmetry

RNS model and its spectrum

• These efforts extended from the independent attempts of Lovelace and Shapiro to obtain the amplitude for the scattering of four pions to the construction of dual models for the scattering of particles with internal symmetry and with spin.
• The first dual model including fermions was obtained by Ramond, as well as the immediately following model proposed by Neveu and Schwarz for extending the Lovelace–Shapiro amplitude to an arbitrary number of pions.
• The Ramond and Neveu–Schwarz models were soon recognized as the two sectors, fermionic and bosonic, of the same model, called the Ramond–Neveu–Schwarz (RNS) model.
• The spectrum contains both fermions and bosons, and is much richer than that of the dual resonance model. Unfortunately, it still contains a tachyon.
• Nevertheless, it was soon recognized, first by Gervais and Sakita, that the RNS model had a new kind of symmetry relating bosons and fermions. This was the first occurrence of supersymmetry.

memo

• http://www-fp.usc.es/~edels/Strings/Lect7Str.pdf
• http://en.wikipedia.org/wiki/GSO_projection