Morrison, David R.Vafa, Cumrun2019-09-221996Morrison, David R., and Cumrun Vafa. 1996. “Compactifications of F-Theory on Calabi-Yau Threefolds. (I).” Nuclear Physics B 473 (1–2): 74–92. https://doi.org/10.1016/0550-3213(96)00242-8.0169-68230550-32131873-1562http://nrs.harvard.edu/urn-3:HUL.InstRepos:41385065We study compactifications of F-theory on certain Calabi-Yau threefolds. We find that N = 2 dualities of type II/heterotic strings in 4 dimensions get promoted to N = 1 dualities between heterotic string and F-theory in 6 dimensions, The six-dimensional heterotic/heterotic duality becomes a classical geometric symmetry of the Calabi-Yau in the F-theory setup. Moreover the F-theory compactification sheds light on the nature of the strong coupling transition and what lies beyond the transition at finite values of heterotic string coupling constant.en-USJournal Article2019-09-2210.1016/0550-3213(96)00242-8