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arXiv · 2210.16276

Soft theorems for boosts and other time symmetries

Lam Hui·Austin Joyce·Ilia Komissarov·Klaas Parmentier·Luca Santoni·Sam S. C. Wong
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Abstract

We derive soft theorems for theories in which time symmetries -- symmetries that involve the transformation of time, an example of which are Lorentz boosts -- are spontaneously broken. The soft theorems involve unequal-time correlation functions with the insertion of a soft Goldstone in the far past. Explicit checks are provided for several examples, including the effective theory of a relativistic superfluid and the effective field theory of inflation. We discuss how in certain cases these unequal-time identities capture information at the level of observables that cannot be seen purely in terms of equal-time correlators of the field alone. We also discuss when it is possible to phrase these soft theorems as identities involving equal-time correlators.

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Lam Hui, Austin Joyce, Ilia Komissarov, Klaas Parmentier, Luca Santoni, Sam S. C. Wong. 2022-10-28. Soft theorems for boosts and other time symmetries. https://doi.org/10.1007/jhep02(2023)123

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