Free Fermion Orientifolds

Understand

We investigate a class of orientifold models based on tensor products of 18 Ising models.

• Using the same search criteria as for the comparable case of Gepner model orientifolds we find that there are no three-family standard model configurations with tadpole cancellation.
• Even if we do not impose the latter requirement, we only find one such configuration in the special case of complex free fermions.
• In order to allow a comparison with other approaches we enumerate the Hodge numbers of the type-IIB theories we obtain.