标题： IIB型弦理论的拓扑约束 显示英文标题

标题： Constraints on the topology of Type IIB string theory

摘要： 我们讨论了一些无法通过基本特征类描述的IIB弦理论上的拓扑约束。 D3-膜的世界体积理论的反常抵消要求Ramond-Ramond 5-形式通量满足一个偏移的狄拉克量子化条件。 然而，所需的偏移有时会根据时空背景的拓扑结构而不一致。 偏移量子化存在的障碍由一个6次上同调类描述，其定义涉及时空流形的自旋结构。 该上同调类被解释为背景D3-电荷，高斯定律约束要求引入额外的D3-膜来抵消它。 显示英文摘要

摘要： We discuss some topological constraints on Type IIB string theory that cannot be described by elementary characteristic classes. Anomaly cancellation of the worldvolume theory of a D3-brane requires a shifted Dirac quantization condition of the Ramond-Ramond 5-form flux. However, the required shift is sometimes inconsistent depending on the topology of spacetime backgrounds. The obstruction to the existence of a shifted quantization is described by a degree-6 cohomology class whose definition involves spin structure of spacetime manifolds. The cohomology class is interpreted as a background D3-charge, and the Gauss law constraint requires inclusion of additional D3-branes to cancel it.