The discussion revolves around the concept of 4-momentum for massless particles, specifically focusing on the implications of different values of k in their 4-momentum representation. The scope includes theoretical considerations and implications for physical properties such as energy, momentum, and their effects on phenomena like light sails.
Participants generally agree on the distinction between the physical properties of massless particles with different 4-momentum values, though the discussion does not resolve any deeper implications or interpretations of these differences.
The discussion does not address potential limitations or assumptions regarding the definitions of energy, momentum, or the implications of masslessness on particle behavior.
I second @Ibix reply. The two particles have the same velocity (speed and direction) but energy and momentum are different and consequently wavelength and frequency.pellman said:The 4-momentum of a massless particle traveling in the z direction is (k, 0, 0, k). What is the significance of the value of k? It does not determine the speed since they always travel at light speed. If one particle has momentum (k, 0, 0, k) and another has (j, 0, 0, j) with j not equal to k, what is the physical difference between them?