Four no-go theorems on the existence of spin and orbital angular momentum of massless bosons

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Hauptverfasser: Palmerduca, Eric, Qin, Hong
Format: Preprint
Veröffentlicht: 2024
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author Palmerduca, Eric
Qin, Hong
author_facet Palmerduca, Eric
Qin, Hong
contents The past decades have seen substantial interest in the so-called orbital angular momentum (OAM) of light, driven largely by its diverse range of applications. However, there are fundamental theoretical issues with decomposing the angular momentum of massless particles, such as photons, into spin (SAM) and orbital angular momentum parts. While the angular momentum of massive particles has a natural splitting into the Wigner SAM and OAM, there are numerous proposed splittings for photons and no consensus about which is correct. Moreover, it has been shown that most of the proposed SAM and OAM operators do not satisfy the defining commutation relations of angular momentum operators and are thus not legitimate splittings. Here, we prove that it is generally impossible to split the total angular momentum operator of massless bosons, such as photons and gravitons, into spin and orbital parts. We prove two further generalizations of this result, showing that there are no SAM-OAM splittings even if (1) the SAM operator generates non-internal symmetries or (2) if one allows the SAM and OAM operators to generate non-SO(3) symmetries.
format Preprint
id arxiv_https___arxiv_org_abs_2407_06276
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Four no-go theorems on the existence of spin and orbital angular momentum of massless bosons
Palmerduca, Eric
Qin, Hong
Mathematical Physics
High Energy Physics - Theory
Optics
The past decades have seen substantial interest in the so-called orbital angular momentum (OAM) of light, driven largely by its diverse range of applications. However, there are fundamental theoretical issues with decomposing the angular momentum of massless particles, such as photons, into spin (SAM) and orbital angular momentum parts. While the angular momentum of massive particles has a natural splitting into the Wigner SAM and OAM, there are numerous proposed splittings for photons and no consensus about which is correct. Moreover, it has been shown that most of the proposed SAM and OAM operators do not satisfy the defining commutation relations of angular momentum operators and are thus not legitimate splittings. Here, we prove that it is generally impossible to split the total angular momentum operator of massless bosons, such as photons and gravitons, into spin and orbital parts. We prove two further generalizations of this result, showing that there are no SAM-OAM splittings even if (1) the SAM operator generates non-internal symmetries or (2) if one allows the SAM and OAM operators to generate non-SO(3) symmetries.
title Four no-go theorems on the existence of spin and orbital angular momentum of massless bosons
topic Mathematical Physics
High Energy Physics - Theory
Optics
url https://arxiv.org/abs/2407.06276