Orientifolds, hypercharge embeddings and the Standard Model Original Research Article

The embedding of the SM hypercharge into an orientifold gauge group is studied. Possible embeddings are classified, and a systematic construction of bottom–up configurations and top–down orientifold vacua is achieved, solving the tadpole conditions in the context of Gepner orientifolds. Some hypercharge embeddings are strongly preferred compared to others. Configurations with chiral anti-symmetric tensors are suppressed. We find among others, genuine examples of supersymmetric image, flipped image, Pati–Salam and trinification vacua with no chiral exotics.