A Brief Discussion on Particle and EM Field Interaction Action
In classical mechanics, to fully describe a particle, one only needs to write down its Lagrangian:
Here, the kinetic term can be regarded as the Action of a free particle, and the potential term is the Action of the interaction between the particle and the field. In electromagnetism, we learn that the field also carries momentum and energy, so the complete description of electromagnetic motion includes the Action of the field:
Originally written in Chinese by the author, these articles are translated into English to invite cross-language resonance.