Is there a theory that explains the mechanism under which photons exceeds the speed of light? It should refer to cases including photons generated in an oscillating charges, dipoles, inhalations, different kind of excitation, accelerated particles, scattering phenomenons etc. Please note that I exclude explanation based on equation of state (energy balance or minimization). For example the energy reduction of an exited electron is the reason for energy formation in terms of electromagnetic radiation but it does not say nothing about the reason it should propagates in the speed of light. In case there are non, then do you familiar with attempts to explain it.