Are there any energy change of photon in different frame?

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Discussion Overview

The discussion revolves around the changes in energy and momentum of photons when observed from different inertial frames, exploring concepts related to the Doppler effect and transformations in special relativity. The scope includes theoretical considerations and mathematical reasoning related to energy-momentum transformations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant inquires about the changes in energy and momentum of photons in different frames and seeks analogies with the Doppler effect.
  • Another participant confirms that photons can experience redshift or blueshift due to the Doppler effect, which is significant in astronomical calculations related to the motion of objects.
  • A further participant questions whether there are changes in energy-momentum of photons beyond the Doppler effect, referencing the Compton process in different frames.
  • A participant provides a detailed explanation of how energy and momentum transform between inertial reference frames using Lorentz transformations, including specific equations for energy and momentum of photons.

Areas of Agreement / Disagreement

Participants express varying degrees of understanding and inquiry regarding the transformation of photon energy and momentum, with some agreement on the role of the Doppler effect, but no consensus on additional changes beyond this effect.

Contextual Notes

The discussion includes assumptions about the applicability of Lorentz transformations and the specific conditions under which energy and momentum are analyzed, particularly in the context of different reference frames.

ndung200790
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Please teach me about this:
Are there any change in energy and momentum of photon in different frame?Are there any analogies with Doppler effect?
Thank you very much in advance.
 
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Yes! Indeed photons can be red or blueshifted, this doppler effect is how we do many calculations in astronomy (e.g. finding the speed of objects moving towards or away from us).
 
Except for Doppler effect,are there any changing in energy-momentum of photon in different frame.Example:Consider Compton process in lab frame and center of mass frame.Because the frequence of photon in Doppler effect depends on the moving towards each other or far away of receiver and sourse
 
Energy and momentum transform between different inertial reference frames exactly the same way as time and position, via the Lorentz transformation.

The time-position four-vector: (ct, x, y, z)

One way to write the energy-momentum four-vector: (E, p_x c, p_y c, p_z c)

If we need to deal only with x-components, the Lorentz transformation for time and position looks like this:

ct^\prime = \gamma (ct - \beta x)

x^\prime = \gamma (x - \beta ct)

For energy and momentum:

E^\prime = \gamma (E - \beta p_x c)

p^\prime_x c = \gamma (p_x c - \beta E)

where as usual \beta = v / c and

\gamma = \frac{1}{\sqrt{1 - v^2 / c^2}} = \frac{1}{\sqrt{1 - \beta^2}}

and v is the relative velocity of the two frames.

For a photon, E = pc, so the Lorentz transformation for the one-dimensional case becomes

E^\prime = \gamma (E - \beta E)

E^\prime = \gamma (1 - \beta) E

E^\prime = \sqrt {\frac {1 - \beta}{1 + \beta}} E
 
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