Bershadsky, MichaelKakushadze, ZurabVafa, Cumrun2019-09-221998Bershadsky, Michael, Zurab Kakushadze, and Cumrun Vafa. 1998. “String Expansion as Large N Expansion of Gauge Theories.” Nuclear Physics B 523 (1–2): 59–72. https://doi.org/10.1016/s0550-3213(98)00272-7.0169-68230550-32131873-1562http://nrs.harvard.edu/urn-3:HUL.InstRepos:41385080We consider string perturbative expansion in the presence of D-branes imbedded in orbifolded space-time. In the regime where the string coupling is weak and alpha' --> 0, the string perturbative expansion coincides with 't Hooft's large N expansion. We specifically concentrate on theories with d = 4 and N = 0, 1, 2, 4, and use world-sheet orbifold techniques to prove vanishing theorems for the field theory beta-functions to all orders in perturbation theory in the large N limit. This is in accord with recent predictions.en-USJournal Article2019-09-2210.1016/S0550-3213(98)00272-7