#### Hall 123

#### Studies of ultra-relativistic macroscopic phenomena including real time correlations

#### Toshali Mitra

##### IMSc

*The existence of hydrodynamic attractors in various microscopic theories and phenomenological models has paved the way for understanding hydrodynamization in out-of- equilibrium systems. The thesis studies a far-away-from equilibrium system in the context of Bjorken model of QGP, boost-invariant expansion along the collisional axis. It explores the effect of continuous symmetry breaking and the corresponding phase transition on hydrodynamization in the Bjorken expanding system and also compute real-time hydrodynamic correlation functions of a system that hydrodynamizes at late time. In addition, we also explore thermalisation in a hybrid system coupled in semi-holographic framework.*

In this presentation, I will discuss the formulation of an effective theory of dissipative superfluid and evolution of the dissipative system in out-of-equilibrium situation in the context of Bjorken flow. I will demonstrate the existence of hydrodynamic attractor and even number of U(1) symmetry breaking fixed points in the unbroken and broken phase of this system. I will discuss a method to compute real time correlation functions of an expanding system using a holographic approach in the limit where the state hydrodynamizes. In this limit, real-time correlation function of the expanding system assumes a thermal form with constant temperature. I will conclude the presentation by providing a generic proof of thermalisation in a hybrid system involving a weakly self- interacting and a strongly self-interacting sector, coupled in a semi-holographic framework.

Done