有些答案不直接給出，是我的教學特點。看一段某數學專著引用楊振寧的話，難道楊振寧數學不好，或沒有比那個數學教授強的地方：

In 1977, the Nobel Prize-winning physicist C. N. Yang wrote in [23], “Gauge fields are deeply related to some profoundly beautiful ideas of contemporary mathematics, ideas that are the driving forces of part of the mathematics of the last 40 years,..., the theory of fiber bundles.” Convinced that gauge fields are related to connections on fiber bundles, he tried to learn the fiber-bundle theory from several mathematical classics on the subject, but “learned nothing. The language of modern mathematics is too cold and abstract for a physicist”。

[23] C. N. Yang, Magnetic monopoles, fiber bundles, and gauge fields, Annals of New York Academy of Sciences 294 (1977), pp. 86–97.