Photon Spin: 1 vs 2 - Answers for Alex

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    Photon Spin
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Discussion Overview

The discussion centers on the spin of photons, specifically whether they possess spin 1 or 2. Participants explore the implications of photon spin in the context of electromagnetic theory, tensor fields, and potential particle models, while also addressing questions about detection and the nature of related particles like gravitons.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants assert that photons have spin 1, referencing the transformation properties of the four-potential as a vector under Lorentz transformations.
  • Others question the nature of the four-potential and its sufficiency in describing detected signals, particularly electric and magnetic fields.
  • There is a discussion about whether a photon with spin 2 can exist, with some participants stating that such a particle cannot be detected as a photon.
  • Some participants propose that spin 2 particles, like gravitons, can be modeled but are distinct from photons, which are characterized as spin 1 particles.
  • There is mention of the historical context of angular momentum in photons, including references to early discoveries and selection rules in atomic transitions.
  • Participants discuss the implications of defining particles with different spins and the conditions under which they can be detected or modeled.

Areas of Agreement / Disagreement

Participants generally agree that photons have spin 1, but there is ongoing debate about the existence and detection of spin 2 particles, particularly in relation to gravitons. The discussion remains unresolved regarding the implications of these differing spins and their detection.

Contextual Notes

Some limitations include the need for clearer definitions of terms like "defined photon" and the conditions under which particles can be modeled or detected. The discussion also reflects varying levels of background knowledge among participants.

Who May Find This Useful

This discussion may be of interest to those studying quantum mechanics, particle physics, and electromagnetic theory, particularly in understanding the complexities of particle spin and its implications in theoretical models.

  • #31
The hypothesis is the change caused by interference in the absorption of photons ...
Spin 2?
 
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  • #32
afcarval,

Evidence that photons have spin 1 comes from the nature of electromagnetic waves. EM waves have a linear polarization, and their effects can described by a vector E perpendicular to the wave. Regarding the source, they can be emitted from a dipole antenna. All of these are characteristic of a spin-1 particle.

By contrast, gravitons (assuming they exist) are spin 2 particles. Gravitational waves would have a much different character. Instead of a transverse vector E they would need to be described by a transverse shear tensor. That is, alternate stretching and compression in both directions perpendicular to the wave. Likewise, the source of the wave would need to be quadrupole. Spin 2 waves could not be emitted by a dipole antenna, since they are quadrupole in nature.
 

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