Yukawa couplings for intersecting D-branes on non-factorisable tori

Abstract

We compute Yukawa couplings in type IIa string theory compactified on a six-torus in the presence of intersecting D6-branes. The six-torus is generated by an SO(12) root lattice. Yukawa couplings are expressed as sums over worldsheet instantons. Our result extends known expressions to a non-factorisable torus. As an aside we also fill in some details for the factorisable torus and non-coprime intersection numbers.

Comments: 36 pages, 7 figures, v2: minor change in argument at end of section 6, references added,v3: typos in (84) and (87) corrected, v4: more typos fixed