The boostless bootstrap: amplitudes without Lorentz boosts
Publication Date
2020-12-30Journal Title
Journal of High Energy Physics
Publisher
Springer Berlin Heidelberg
Volume
2020
Issue
12
Language
en
Type
Article
This Version
VoR
Metadata
Show full item recordCitation
Pajer, E., Stefanyszyn, D., & Supeł, J. (2020). The boostless bootstrap: amplitudes without Lorentz boosts. Journal of High Energy Physics, 2020 (12) https://doi.org/10.1007/jhep12(2020)198
Abstract
Abstract: Poincaré invariance is a well-tested symmetry of nature and sits at the core of our description of relativistic particles and gravity. At the same time, in most systems Poincaré invariance is not a symmetry of the ground state and is hence broken spontaneously. This phenomenon is ubiquitous in cosmology where Lorentz boosts are spontaneously broken by the existence of a preferred reference frame in which the universe is homogeneous and isotropic. This motivates us to study scattering amplitudes without requiring invariance of the interactions under Lorentz boosts. In particular, using on-shell methods and assuming massless, relativistic and luminal particles of any spin, we show that the allowed interactions around Minkowski spacetime are severely constrained by unitarity and locality in the form of consistent factorization. The existence of an interacting massless spin-2 particle enforces (analytically continued) three-particle amplitudes to be Lorentz invariant, even those that do not involve a graviton, such as cubic scalar couplings. We conjecture this to be true for all n-particle amplitudes. Also, particles of spin S > 2 cannot self-interact nor can be minimally coupled to gravity, while particles of spin S > 1 cannot have electric charge. Given the growing evidence that free gravitons are well described by massless, luminal relativistic particles, our results imply that cubic graviton interactions in Minkowski must be those of general relativity up to a unique Lorentz-invariant higher-derivative correction of mass dimension 9. Finally, we point out that consistent factorization for massless particles is highly IR sensitive and therefore our powerful flat-space results do not straightforwardly apply to curved spacetime.
Keywords
Regular Article - Theoretical Physics, Scattering Amplitudes, Spontaneous Symmetry Breaking, Space-Time Sym- metries
Identifiers
jhep12(2020)198, 14487
External DOI: https://doi.org/10.1007/jhep12(2020)198
This record's URL: https://www.repository.cam.ac.uk/handle/1810/315649
Rights
Attribution 4.0 International (CC BY 4.0)
Licence URL: https://creativecommons.org/licenses/by/4.0/
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