Effective field theory of gravitating continuum: solids, fluids, and aether unified

Abstract We investigate the relativistic effective field theory (EFT) describing a non-dissipative gravitating continuum. In addition to ordinary continua, namely solids and fluids, we find an extraordinary more symmetric continuum, aether. particular, symmetry of aether concludes that homogeneous isotropic state behaves like cosmological constant. formulate EFT in unitary/comoving gauge which dynamical degrees freedom continuum (phonons) are eaten by spacetime metric. This choice, is interpreted as Lagrangian description hydrodynamics, offers neat geometrical understanding continua. examine thread-based decomposition with respect four-velocity different from foliation-based Arnowitt-Deser-Misner one. Our respects symmetries continua and, therefore, makes it possible systematically invariant building blocks for each even at higher orders derivative expansion. also discuss linear dynamics system show both gravitons phonons acquire “masses” background.