U(1) quasi-hydrodynamics: Schwinger-Keldysh effective field theory and holography

Understand

We study the quasi-hydrodynamics of a system with a softly broken $U(1)$ global symmetry using effective field theory (EFT) and holographic methods.

• In the gravity side, we consider a holographic Proca model in the limit of small bulk mass, which is responsible for a controllable explicit breaking of the $U(1)$ global symmetry in the boundary field theory.
• We perform a holographic Schwinger-Keldysh analysis, which allows us to derive the form of the boundary effective action in presence of dissipation.
• We compare our results with the previously proposed EFT and hydrodynamic theories, and we confirm their validity by computing the low-energy quasi-normal modes spectrum analytically and numerically.