Symmetric superfluids

  • Enrico Pajer
  • David StefanyszynEmail author
Open Access
Regular Article - Theoretical Physics


We present a complete classification of symmetric superfluids, namely shift-symmetric and Poincaré invariant scalar field theories that have an enlarged set of classically conserved currents at leading order in derivatives. These theories arise in the decoupling limit of the effective field theory of shift-symmetric, single-clock cosmologies and our results pick out all models with couplings fixed by additional symmetry. Remarkably, in D ≥ 2 spacetime dimensions there are only two possibilities: the Dirac-Born-Infeld theory and Scaling Superfluids with Lagrangian (−∂μϕμϕ)α, for some real α. The scaling symmetry present for any α is further enhanced to the full conformal group only for α = D/2, and to infinitely many additional generators for the cuscuton, namely α = 1/2. We discuss the stability of Scaling Superfluids and point out that all coupling constants are determined by the speed of sound.


Effective Field Theories Global Symmetries Space-Time Symmetries 


Open Access

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Copyright information

© The Author(s) 2019

Authors and Affiliations

  1. 1.DAMTP, Centre for Mathematical SciencesUniversity of CambridgeCambridgeU.K.
  2. 2.Van Swinderen Institute for Particle Physics and GravityUniversity of GroningenGroningenThe Netherlands

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