Does photon have upper limit energy ?

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Photons do not have an upper limit on energy, even beyond gamma rays. The Planck energy is significant but not a definitive limit, as current quantum field theory (QFT) does not impose a maximum energy for photons. However, issues arise at the Planck energy due to the influence of gravity, which is not accounted for in QFT. Additionally, QFT is considered a low-energy effective theory, suggesting that its predictions may break down at high energies. Thus, while theoretically unlimited, practical constraints exist at extreme energy levels.
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.
 
Time reversal invariant Hamiltonians must satisfy ##[H,\Theta]=0## where ##\Theta## is time reversal operator. However, in some texts (for example see Many-body Quantum Theory in Condensed Matter Physics an introduction, HENRIK BRUUS and KARSTEN FLENSBERG, Corrected version: 14 January 2016, section 7.1.4) the time reversal invariant condition is introduced as ##H=H^*##. How these two conditions are identical?

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