Spacetimes that include a boundary at infinity have a nontrivial topology. The homology of the background influences gauge fields living on them and leads to topological charges. We investigate the charges and fluxes of fields over a Taub–NUT background in Einstein–Maxwell dilaton-axion gravity, by using the relative homology and de Rham cohomology. It turns out that the electromagnetic sector is devoid of restrictions from a topological viewpoint. There are, however, flux quanta for the axion and dilaton fields. These results are obtained from the absolute homology of the spacetime boundary. The solutions we probe originate in the four-dimensional low energy limit of heterotic string theory. So our results are complemented by the stringy coupling present in the fields. The quantization has a bundle theoretic interpretation as the axion's flux corresponds to the topological index of an underlying 2-bundle.

中文翻译：

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Dilatonic Taub–Nut Dyons 中的通量量化

包含无穷远边界的时空具有非平凡的拓扑结构。背景的同源性影响存在于它们上的规范场并导致拓扑电荷。我们通过使用相对同调和 de Rham 上同调研究了爱因斯坦-麦克斯韦膨胀轴引力中 Taub-NUT 背景上场的电荷和通量。事实证明，从拓扑的角度来看，电磁扇区是没有限制的。然而，存在轴子和膨胀子场的通量量子。这些结果是从时空边界的绝对同源性中获得的。我们探索的解决方案起源于异质弦理论的四维低能量极限。因此，我们的结果得到了领域中存在的粘性耦合的补充。量化具有束理论解释为轴'