Speaker
Description
Recent developments in the Schwinger–Keldysh (SK) formalism have enabled significant progress in the construction of effective field theories (EFTs) for out-of-equilibrium systems at finite temperature. Nevertheless, existing results in the literature lack a systematic and transparent framework for deriving SK EFT actions for generic fluid systems. In this talk, I will apply the coset construction method – adapted for possible breaking of spacetime symmetries – to derive SK EFT Lagrangians at first dissipative order, which describe generic fluid systems. These are systems whose ground state spontaneously breaks spacetime symmetries in a way characteristic of fluids, without imposing any specific assumption on the internal symmetry content. Focusing on $U(1)$-charged fluids and superfluids as concrete examples, I will derive phenomenological consequences, including local equilibrium thermodynamic relations, the entropy current and the local second law of thermodynamics, and dissipative dispersion relations. All results are consistent with previously known outcomes in the literature, thereby reinforcing the validity and potential of the approach.