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

Abstract

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. Additionally, we derive the broken holographic Ward identity for the U(1) current, and discuss the recently proposed novel transport coefficients for systems with explicitly broken symmetries. The setup considered is expected to serve as a toy model for more realistic situations where quasi-hydrodynamics is at work, such as axial charge relaxation in QCD, spin relaxation in relativistic systems, electric field relaxation in magneto-hydrodynamics, or momentum relaxation in condensed matter systems.

Climate Change and Hydropower Development in the Eastern Himalaya: Emerging Conflicts in the Upper Tista Catchment of Sikkim, India

“…It has become a very powerful theoretical tool for studying strongly coupled systems. It has a wide application in different fields of physics, such as condensed matter physics, hydrodynamics and QCD [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] to name a few. Our study will be focused on the application of the fluid/gravity correspondence in the context of hydrodynamics, in particular the study of the anomalous transport in this kind of systems.…”