The GSO projection, BRST cohomology and picture-changing in N = 2 string theory

Jan Bischoff, Sergei V. Ketov, Olaf Lechtenfeld

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)


We investigate in detail the critical N = 2 fermionic string with and without a global Z2 twist. An analysis of BRST cohomology shows that twisted sectors contain massless 'spacetime' fermions which are non-local with respect to the standard massless boson. However, two distinct GSO projections exist, one (untwisted) retaining merely the usual boson and its spectral-flow partner, the other (twisted) yielding two fermions and one boson, on the massless level. The corresponding chiral BRST-invariant vertex operators are constructed in certain pictures, and their fusion and picture-changing are investigated, including the construction of inverse picture-changing operators. The N = 2 'spacetime supersymmetry' generators are null operators, since the twisted massless states fail to interact. The untwisted three- and four-point functions are recalculated at tree-level.

Original languageEnglish
Pages (from-to)373-409
Number of pages37
JournalNuclear Physics, Section B
Issue number1-2
Publication statusPublished - 27 Mar 1995

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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