Speaker
Description
The rapid longitudinal expansion in the early stage of relativistic heavy-ion collisions drives the system far from equilibrium, generating large pressure anisotropies that challenge standard viscous hydrodynamics (VH). Viscous Anisotropic Hydrodynamics (VAH) addresses this by non-perturbatively resumming these anisotropies and has shown phenomenological success in describing flow observables. However, a systematic theoretical understanding of its fundamental properties, in particular the interplay between anisotropic expansion and momentum relaxation, remains incomplete. In this work, we perform a linearized analysis of conformal VAH around anisotropic backgrounds. Deriving the dispersion relations, we identify four eigenmodes and show that pressure anisotropy breaks rotational symmetry, introducing a dependence on the perturbation angle. We find that the momentum relaxation directly shapes the dissipative properties of each mode. To further understand early-stage dynamics, we extend the analysis to a Bjorken-expanding background and examine the interplay between momentum relaxation and system expansion, as well as its impact on the response properties. Our analysis provides deeper theoretical insight into the nature of VAH and offers guidance for its application to early-stage QGP dynamics.
