Continuous-spin particles, on shell
Abstract We study on-shell scattering amplitudes for continuous-spin particles (CSPs). Poincaré invariance, little-group ISO(2) covariance, analyticity, and on-shell factorisation (unitarity) impose stringent conditions on these amplitudes. We solve them by realizing a non-trivial representation for...
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| Format: | Article |
| Language: | English |
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SpringerOpen
2025-05-01
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| Series: | Journal of High Energy Physics |
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| Online Access: | https://doi.org/10.1007/JHEP05(2025)166 |
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| author | Brando Bellazzini Stefano De Angelis Marcello Romano |
| author_facet | Brando Bellazzini Stefano De Angelis Marcello Romano |
| author_sort | Brando Bellazzini |
| collection | DOAJ |
| description | Abstract We study on-shell scattering amplitudes for continuous-spin particles (CSPs). Poincaré invariance, little-group ISO(2) covariance, analyticity, and on-shell factorisation (unitarity) impose stringent conditions on these amplitudes. We solve them by realizing a non-trivial representation for all little-group generators on the space of functions of bi-spinors. The three-point amplitudes are uniquely determined by matching their high-energy limit to that of definite-helicity (ordinary) massless particles. Four-point amplitudes are then bootstrapped using consistency conditions, allowing us to analyze the theory in a very transparent way, without relying on any off-shell Lagrangian formulation. We present several examples that highlight the main features of the resulting scattering amplitudes. We discuss CSP’s amplitudes as a new infrared deformation of ordinary massless amplitudes, which is controlled by the scale of the Pauli-Lubanski vector squared, as opposed to the familiar mass deformation. Finally, we explore under which conditions it is possible to relax some assumptions, such as strict on-shell factorisation, analyticity, or others. In particular, we also investigate how continuous-spin particles may couple to gravity and electromagnetism, in a loose version of S-matrix principles. |
| format | Article |
| id | doaj-art-d13ac9d8ecfe4b5c9657af66a0245caa |
| institution | Kabale University |
| issn | 1029-8479 |
| language | English |
| publishDate | 2025-05-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Journal of High Energy Physics |
| spelling | doaj-art-d13ac9d8ecfe4b5c9657af66a0245caa2025-08-20T03:25:15ZengSpringerOpenJournal of High Energy Physics1029-84792025-05-012025514210.1007/JHEP05(2025)166Continuous-spin particles, on shellBrando Bellazzini0Stefano De Angelis1Marcello Romano2Université Paris-Saclay, CNRS, CEA, Institut de Physique ThéoriqueUniversité Paris-Saclay, CNRS, CEA, Institut de Physique ThéoriqueUniversité Paris-Saclay, CNRS, CEA, Institut de Physique ThéoriqueAbstract We study on-shell scattering amplitudes for continuous-spin particles (CSPs). Poincaré invariance, little-group ISO(2) covariance, analyticity, and on-shell factorisation (unitarity) impose stringent conditions on these amplitudes. We solve them by realizing a non-trivial representation for all little-group generators on the space of functions of bi-spinors. The three-point amplitudes are uniquely determined by matching their high-energy limit to that of definite-helicity (ordinary) massless particles. Four-point amplitudes are then bootstrapped using consistency conditions, allowing us to analyze the theory in a very transparent way, without relying on any off-shell Lagrangian formulation. We present several examples that highlight the main features of the resulting scattering amplitudes. We discuss CSP’s amplitudes as a new infrared deformation of ordinary massless amplitudes, which is controlled by the scale of the Pauli-Lubanski vector squared, as opposed to the familiar mass deformation. Finally, we explore under which conditions it is possible to relax some assumptions, such as strict on-shell factorisation, analyticity, or others. In particular, we also investigate how continuous-spin particles may couple to gravity and electromagnetism, in a loose version of S-matrix principles.https://doi.org/10.1007/JHEP05(2025)166Scattering AmplitudesEffective Field TheoriesSpace-Time Symmetries |
| spellingShingle | Brando Bellazzini Stefano De Angelis Marcello Romano Continuous-spin particles, on shell Journal of High Energy Physics Scattering Amplitudes Effective Field Theories Space-Time Symmetries |
| title | Continuous-spin particles, on shell |
| title_full | Continuous-spin particles, on shell |
| title_fullStr | Continuous-spin particles, on shell |
| title_full_unstemmed | Continuous-spin particles, on shell |
| title_short | Continuous-spin particles, on shell |
| title_sort | continuous spin particles on shell |
| topic | Scattering Amplitudes Effective Field Theories Space-Time Symmetries |
| url | https://doi.org/10.1007/JHEP05(2025)166 |
| work_keys_str_mv | AT brandobellazzini continuousspinparticlesonshell AT stefanodeangelis continuousspinparticlesonshell AT marcelloromano continuousspinparticlesonshell |