[數撚圍爐區] Let ε < 0. (9)

其實物理佬都係solve 條de再impose physical initial / boundary conditions 再make sense堆solution?

冇拉褲鏈？

物理有分兩種，一種scalar一種vector
Scalar potential又分好多，起gravitational 或者em可以諗成energy
Vector potential都一樣，但起em唔可以諗成energy, 因為呢個vector potential related to magnetic field, which does not do work.
去到qm又唔同睇法，但之後要等其他巴打補充

其中一個原因係用potential方便過用force做數
例如你define lagrangian或者Hamiltonian會方便過你用 F=ma寫equation of motion
仲有其他原因，但唔識了

最少起physics, vector potential 都係一個fundamental concept
起quantum theory會見到好多

ug phy好似唔會起qm掂到vector potential