We construct global orientifold limits of singular F-theory vacua whose associated gauge groups are SO(3), SO(5), SO(6), $F_4$, SU(4), and Spin(7). For each limit we show a universal tadpole relation is satisfied, which is a homological identity whose dimension-zero component encodes the matching of the D3 charge between each F-theory compactification and its orientifold limit. While for smooth F-theory compactifications which admit global orientifold limits the contribution to the associated universal tadpole relation comes from its Chern class, we show that for all singular F-theory compactifications under consideration, the contribution to the universal tadpole relation comes from its stringy Chern class. Moreover, the brane spectrum associated with each of our limits consists solely of smooth branes, as opposed to the Sen limit which necessarily involves singular branes.

我们构造奇异F理论真空的全局方向极限，其相关的标度组为SO（3），SO（5），SO（6），$F_4$，SU（4）和Spin（7）。对于每个极限，我们表明满足了一个通用的ad关系，这是一个同源性，其零维分量编码每个F理论压实度和其取向极限之间D3电荷的匹配。尽管对于允许全局方向限制的平稳F理论紧致化限制了对关联的通用t关系的贡献来自其Chern类，但我们表明，对于所考虑的所有奇异F理论紧致化，对通用t关系的贡献都来自于其严格性。陈班。此外，与我们的每个限制相关的麸谱仅由光滑的麸组成，而不是与Sen限制相对应的Sen限制，后者必然涉及奇异的麸。