SciPost Phys. 12, 142 (2022) ·
published 29 April 2022
We consistently couple simple continuum field theories with fracton
excitations to curved spacetime backgrounds. We consider homogeneous and
isotropic fracton field theories, with a conserved $U(1)$ charge and dipole
moment. Coupling to background fields allows us to consistently define a
stress-energy tensor for these theories and obtain the respective Ward
identities. Along the way, we find evidence for a mixed gauge-gravitational
anomaly in the symmetric tensor gauge theory which naturally couples to
conserved dipoles. Our results generalise to systems with arbitrarily higher
conserved moments, in particular, a conserved quadrupole moment.
SciPost Phys. 11, 054 (2021) ·
published 10 September 2021
We formulate the Schwinger-Keldysh effective field theory of hydrodynamics without boost symmetry. This includes a spacetime covariant formulation of classical hydrodynamics without boosts with an additional conserved particle/charge current coupled to Aristotelian background sources. We find that, up to first order in derivatives, the theory is characterised by the thermodynamic equation of state and a total of 29 independent transport coefficients, in particular, 3 hydrostatic, 9 non-hydrostatic non-dissipative, and 17 dissipative. Furthermore, we study the spectrum of linearised fluctuations around anisotropic equilibrium states with non-vanishing fluid velocity. This analysis reveals a pair of sound modes that propagate at different speeds along and opposite to the fluid flow, one charge diffusion mode, and two distinct shear modes along and perpendicular to the fluid velocity. We present these results in a new hydrodynamic frame that is linearly stable irrespective of the boost symmetry in place. This provides a unified covariant stable approach for simultaneously treating Lorentzian, Galilean, and Lifshitz fluids within an effective field theory framework and sets the stage for future studies of non-relativistic intertwined patterns of symmetry breaking.
Submissions for which this Contributor is identified as an author:
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