Speaker
Description
Relativistic hydrodynamics has played a key role in our understanding of the novel properties of quark-gluon plasma. However, the validity of hydrodynamical models in describing the extreme conditions produced in heavy ion collisions has still not been properly justified theoretically. Even more, the gradient expansion, commonly used to derive hydrodynamics from microscopic theory, has been recently shown to diverge for conformal fluids or relativistic gases undergoing Bjorken flow [1,2], putting under question the definition of hydrodynamics itself.
In this contribution, another approach to derive relativistic hydrodynamics from the Boltzmann equation is discussed: the method of moments [3]. We investigate the convergence of this approximation scheme under Bjorken flow and Gubser flow and show that, in contrast to the gradient expansion, the method of moments appears to be convergent. Finally, we discuss whether there is an attractor for solutions of the full Boltzmann equation, both in the relaxation time approximation and for a collision term including elasctic 2-to-2 collisions.
[1] M. P. Heller and M. Spalinski, "Hydrodynamics Beyond the Gradient Expansion: Resurgence and Resummation," Phys. Rev. Lett. 115, no. 7, 072501 (2015).
[2] G. S. Denicol and J. Noronha, "Analytical attractor and the divergence of the slow-roll expansion in relativistic hydrodynamics,'' Phys.Rev. D97 (2018) no.5, 056021.
[3] G. S. Denicol, H. Niemi, E. Molnar, and D. H. Rischke, "Derivation of transient relativistic fluid dynamics from the Boltzmann equation," Phys. Rev. D 85, 114047 (2012).