Akash Jain

University of Amsterdam


Stability, Causality, and Unitarity of Relativistic Schwinger-Keldysh Hydrodynamics


QFT/Holography Seminar


4th November 2024, 2:00 pm – 3:00 pm
Fry Building, 4th Floor Seminar Room


In recent years, a new effective field theory (EFT) paradigm for hydrodynamics has emerged that promises to describe non-equilibrium dissipative and stochastic phenomena starting from a symmetry-based action principle. Like any EFT, the EFT for hydrodynamics requires a UV regularisation prescription for performing (stochastic or quantum) loop calculations. The story is particularly subtle for relativistic hydrodynamics, where a suitably engineered UV sector is needed even at the classical level to ensure the stability and causality of boosted hydrodynamic states. In this talk, we will discuss stable and causal UV regularisation in the EFT framework of relativistic hydrodynamics. In particular, we will examine how these prescriptions interplay with the local Kubo-Martin-Schwinger (KMS) symmetry, which enforces fluctuation-dissipation relations. Interestingly, we find that the newly discovered causal and stable formulation of first-order relativistic hydrodynamics, called Bemfica-Disconzi-Noronha-Kovtun (BDNK) hydrodynamics, is incompatible with the inclusion of stochastic fluctuations. The talk will be based on arXiv:2309.00511.





Organisers: Vaios Ziogas, Mike Blake

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