Does photon have upper limit energy ?

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Discussion Overview

The discussion centers on whether there is an upper limit to the energy of a photon, particularly in relation to the Planck energy and gamma-ray energies. Participants explore theoretical implications and the relationship between photon energy and fundamental physical constants.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that the Planck scale may represent an ultimate limit, with implications for photon wavelengths shorter than the Planck length.
  • Others argue that while the Planck energy is significant, it does not constitute an upper limit for photon energy.
  • One participant mentions that frequencies exceeding the inverse Planck time may lack meaning in current theories, complicating the definition of photon energies beyond a certain threshold.
  • A later reply discusses the absence of an official upper limit in current quantum field theory (QFT) but highlights potential issues around the Planck energy due to the influence of gravity, which is not accounted for in QFT.
  • Another point raised is that QFT may only be a low-energy effective theory, suggesting limitations in its applicability at high energies.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether there is an upper limit to photon energy. Multiple competing views are presented, with some asserting no upper limit exists while others caution about the implications of high-energy photons in relation to gravity and the limitations of QFT.

Contextual Notes

Participants note that the discussion involves unresolved assumptions regarding the interplay between gravity and quantum mechanics, as well as the limitations of current theoretical frameworks at high energies.

magnetar
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Does photon have upper limit energy ?

Does photon have upper limit energy(beyond gamma-ray) ?Thank you !
 
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mmm...not really sure... but perhaps the Planck scale is the ultimate (so far)... you may have problems if your photon wavelength is shorter than the Planck length or at least the rules of the game may change (?)
 
yes- Planck energy- a photon at Planck energy would have a wavelength equal to the Planck length-
 
magnetar said:
Does photon have upper limit energy(beyond gamma-ray) ?Thank you !
No. There is no upper limit.
The Planck energy is large, but is not a limit.
 
You may consider that a frequency higher than an inverse Planck time is not meaningful in current theories, so that we cannot give a clear meaning to a photon energy higher than 1/sqrt (hbar * G / c^5) * h.
 
In current QFT, which is at the origin of the concept of what is a "photon", there is no official upper limit on what is the maximal energy of a photon.
However, there are two caveats:
- the first is that gravity (which is NOT included in QFT as we know it), suggests that there will be trouble around the Planck energy. In other words, we think that whatever QFT might say about arbitrarily high energies, it will not be correct because gravity will not only be not neglegible (as it is assumed in QFT), but it will rather be so dominant that it is meaningless to try to work with a theory that doesn't contain gravity
- QFT itself, as we know it, has a serious problem at high energies. We think that current QFT are "low energy effective" approximations to something else, and this approach is what justifies renormalisation schemes. This has nothing to do with Planck scales, but rather with the intrinsic structure of QFT.
 

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