Can there be massive photons? A pedagogical glance at the origin of mass

Abstract

Among the most startling experiences a student encounters is learning that, unlike electrons and other elementary particles, photons have no mass. Under certain circumstances, however, the light quantum behaves as if it did have a finite mass. Starting from Maxwell's equations, we discuss how this arises when light interacts with a charged plasma, or travels along a waveguide. The motion of such photons is analysed using kinematic concepts of special relativity, and we show how a cutoff frequency for effective propagation appears. Seeing how an environment may yield an apparent dynamic mass to the photon paves the way for later understanding: might the Higgs boson field provide other particles, such as the electron, with a mass? This paper is addressed to mid-level physics students, teachers and lecturers, requiring only a knowledge of classical electromagnetic and special relativity theories.

Consistency of an alternative CPT-odd and Lorentz-violating extension of QED

“…in which ∆ (0) µν , the zeroth-order term in κ µ , is the photon propagator of the traditional QED, ∆ (1) µν is the contribution to the propagator in first order in κ µ and so on. The expansion can be diagrammatically represented by Fig.…”

“…It is important to remember that in the graph of Fig. 4a, the photon line with one insertion means the term ∆ (1) µν in the expansion of the photon propagator. These two contributions furnish the results…”

“…A direct consequence of an exact gauge symmetry in QED is that photons must be massless. Physical effects beyond Maxwell electromagnetism were extensively discussed in the context of Proca model [1,2]. Regarding the effective character of this symmetry, it may be possible that photons have a very small but nonvanishing rest mass m γ .…”

Photon Propagation Through Dispersive Media

“…For example, see Ref. [16]. For flow along the waveguide axis, the action of confinement may be viewed as yielding longitudinal photons propagating with a mass proportional to the cut-off frequency of the corresponding electromagnetic mode.…”

“…Equation 35may be related with the description in terms of massive photons propagating in a plasma: As shown in Ref. [16], the presence of the plasma decreases the rate of electromagnetic energy flow, reaching a zero speed when ℏω ¼ ℏω p ¼ m γ c 2 , a photon energy below which the propagation is not possible.…”