Dopler Shift and Photon Number

[cmos]

Here's something that I recently thought about:

If we assume a Doppler shifted EM wave retains the amplitude of the unshifted wave, then we must be creating/annihilating photons. This seems consistent with the conservation of energy; the removal of several photons removes energy from the system but this energy is conserved by the increase in energy of the remaining photons, as would be the case of a blue shift.

Does this seam reasonable?

I realize that number conservation of photons is never a requirement, but it originally bothered me that photons can just come in and out of existence in the manner described above. My explanation for this is that during a Doppler shift, a single photon is either joining with several others or splitting into several others in a manner that conserves energy.

Does this seem reasonable?

 

[lbrits]

Probably a good idea to look into coherent states and bogoliubov transformations.

 

[Meir Achuz]

The Doppler shift does not change the number of photons.
The frequency, energy and momentum of each photon changes.

 

[cmos]

The Doppler shift does not change the number of photons.
The frequency, energy and momentum of each photon changes.

If the number of photons does not change, then a change in wavelength will induce a change in amplitude. For the amplitude to remain the same, the number of photons must change - hence my original post.

lbrits, I will be looking into it...

 

[malawi_glenn]

related paper: http://arxiv.org/ftp/physics/papers/0407/0407077.pdf

 

[Meir Achuz]

If the number of photons does not change, then a change in wavelength will induce a change in amplitude. For the amplitude to remain the same, the number of photons must change - hence my original post.
lbrits, I will be looking into it...

Why do you assume the amplitude won't change? The E and B fields change in a Lorentz transformation.
Consider light so weak that there is only one photon.
Could a small change in frequency add or subtract a photon?