Speaker
Description
Despite the success of hydrodynamic models in describing relativistic heavy-ion collisions, questions persist about their regime of validity. Non-linear causality conditions provide a clear criterion for assessing the applicability of models. If the evolution of a system violates causality, it cannot reliably represent the underlying relativistic theory. It is now known that state-of-the-art hydrodynamic simulations enter an acausal regime, at least sometimes. Here we explore the phenomenological consequences of enforcing causality constraints in modern Bayesian parameter estimations of heavy-ion collisions. We find that, while only a small fraction of the system’s energy typically enters an acausal regime at the onset of hydrodynamic evolution, strictly limiting this fraction impacts the inferred initial conditions of the system. This leads to notable shifts in the preferred parameters for QGP properties, including a substantial reduction in the favored values of bulk viscosity. These results underscore the importance of refining theoretical models of the out-of-equilibrium dynamics in the early stages of heavy-ion collisions to ensure more accurate representations of QGP properties.
Based on: arXiv:2409.17127
| Category | Theory |
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