Dr. Ding Ding (zoom) (Fudan University) Effective dynamics of quantum fluctuations with applications to cosmology

Quantum fluctuations can be thought of as new degrees-of-freedom (DoFs) on top of the original classical system. In this talk, I will introduce a (canonical) effective framework that encodes quantum fluctuations as additional independent DoFs within an enlarged phase space. In this framework, there is a dynamic two-way communication between classical variables and quantum fluctuations, making it suitable for describing time-dependent quantum backreaction.
I will apply our effective framework to examples in both flat and curved spacetimes. We will discover the key roles played by spatial symmetries and the uncertainty principle. The former helps us decouple fluctuations from each other and minimize backreaction on background inhomogeneities. The uncertainty principle, on the other hand, will help us select out minimal-energy configurations. At the leading order, these configurations coincide with ones dictated by textbook (1PI) effective potentials.
If time permits I will mention some potential future applications.