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Massless contraction of massive particles in the infinite boost limit
Abstract
Massless particles, defined through Wigner's induced representations of the Poincaré group, are obtained as a limit of infinitely boosted massive particles wherein the massive little group undergoes an Inönü--Wigner contraction to the massless one. It is demonstrated that the spin-s multiplet of a massive representation re-organizes into the direct sum of massless particles with helicities in the range [−s,s]. This group theoretic result is the Hilbert space counterpart of the Stückelberg formulation of massive fields of spin s in the high-energy limit, where the Stückelberg fields become independent massless fields of spins s'≤ s in integer steps. It therefore also provides the kinematic setting of the Goldstone equivalence theorem.
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BibTeX
@misc{nguyen2026massless,
title = {{Massless contraction of massive particles in the infinite boost limit}},
author = {Kevin Nguyen},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.11364},
eprint = {2609.11364},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.11364},
}
RIS
TY - UNPB
TI - Massless contraction of massive particles in the infinite boost limit
AU - Kevin Nguyen
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2609.11364
UR - https://arxiv.org/abs/2609.11364
AB - Massless particles, defined through Wigner's induced representations of the Poincaré group, are obtained as a limit of infinitely boosted massive particles wherein the massive little group undergoes an Inönü--Wigner contraction to the massless one. It is demonstrated that the spin-s multiplet of a massive representation re-organizes into the direct sum of massless particles with helicities in the range [−s,s]. This group theoretic result is the Hilbert space counterpart of the Stückelberg formulation of massive fields of spin s in the high-energy limit, where the Stückelberg fields become independent massless fields of spins s'≤ s in integer steps. It therefore also provides the kinematic setting of the Goldstone equivalence theorem.
ER -