Higher order couplings from heterotic orbifold theory

Kang Sin Choi, Tatsuo Kobayashi

Research output: Contribution to journalArticlepeer-review

42 Scopus citations


We calculate couplings of arbitrary order from correlation functions among twisted strings, using conformal field theory. Twisted strings arise in heterotic string compactified on orbifolds yielding matter fields in the low energy limit. We calculate completely the classical and the quantum amplitude including normalization, up to a contribution from Kähler potential. The classical action has saddle points which are interpreted as worldsheet instantons described by metastable untwisted strings, formed by twisted strings distributed at certain fixed points. This understanding generalizes the area rule, in the case that the locations of twisted strings do not form a polygon, and provides a general rule for calculating these kinds of instanton corrections. An interpretation of couplings involving linearly combined states is given, which commonly appear in non-prime order orbifolds. The quantum part of the amplitude is given by ratios of gamma functions with order one arguments.

Original languageEnglish
Pages (from-to)295-321
Number of pages27
JournalNuclear Physics, Section B
Issue number1-2
StatePublished - 1 Jul 2008


  • Heterotic string
  • Higher order coupling
  • Orbifold compactification
  • Yukawa coupling


Dive into the research topics of 'Higher order couplings from heterotic orbifold theory'. Together they form a unique fingerprint.

Cite this