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arXiv · 2301.11363

Soft Phonon Theorems

Clifford Cheung·Maria Derda·Andreas Helset·Julio Parra-Martinez
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Abstract

A variety of condensed matter systems describe gapless modes that can be interpreted as Nambu-Goldstone bosons of spontaneously broken Poincar\'e symmetry. In this paper we derive new soft theorems constraining the tree-level scattering of these degrees of freedom, as exhibited in solids, fluids, superfluids, and framids. These soft theorems are in one-to-one correspondence with various broken symmetries, including spacetime translations, Lorentz boosts, and, for the case of fluids, volume-preserving diffeomorphisms. We also implement a bootstrap in which the enhanced vanishing of amplitudes in the soft limit is taken as an input, thus sculpting out a subclass of exceptional solid, fluid, and framid theories.

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Clifford Cheung, Maria Derda, Andreas Helset, Julio Parra-Martinez. 2023-01-26. Soft Phonon Theorems. https://doi.org/10.1007/jhep08(2023)103

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