In lasers electrons are excited, in free-electron lasers electrons are periodically accelerated as well as in radio antennas. Radiation is produced when deflected in a magnetic field. Thermal excitation of subatomic particles produces EM radiation. Etc.
Can EM radiation be produced by anything other than the excitation and acceleration of charges?
Note: The question Is accelerating charges only way to produce EM radiation? What about gamma from nucleus? poses only the acceleration of electrons against that of the nucleus. I want to know if the enumeration of acceleration and excitation are the only causes of EM radiation.
