Orientifold Calabi-Yau Threefolds with Divisor Involutions and String Landscape

Understand

We establish an orientifold Calabi-Yau threefold database for $h^{1,1}(X) \leq 6$ by considering non-trivial $\mathbb{Z}_{2}$ divisor exchange involutions, using a toric Calabi-Yau database (http://www.rossealtman.com/toriccy/).

• We first determine the topology for each individual divisor (Hodge diamond), then identify and classify the proper involutions which are globally consistent across all disjoint phases of the K\"ahler cone for each unique geometry.
• Each of the proper involutions will result in an orientifold Calabi-Yau manifold.
• Then we clarify all possible fixed loci under the proper involution, thereby determining the locations of different types of $O$-planes.