Paths to equilibrium in non-conformal collisions
Departament de Física Quàntica i Astrofísica & Institut de Ciències del Cosmos (ICC), Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
2 Instituto Galego de Física de Altas Enerxías (IGFAE), Universidade de Santiago de Compostela, 15782 Galicia, Spain
3 Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP, United Kingdom
4 Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys 23, 08010, Barcelona, Spain
5 Institut de Ciències de I’Espai (CSIC-IEEC), Campus UAB, Carrer de Can Magrans s/n, 08193 Cerdanyola del Vallès, Spain
6 CENTRA, Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais 1, 1049 Lisboa, Portugal
* Speaker, e-mail: email@example.com
Published online: 26 March 2018
Ever since fast hydrodynamization has been observed in heavy ion collisions the understanding of the hot early out-of-equilibrium stage of such collisions has been a topic of intense research. We use the gauge/gravity duality to model the creation of a strongly coupled Quark-Gluon plasma in a non-conformal gauge theory. This numerical relativity study is the first non-conformal holographic simulation of a heavy ion collision and reveals the existence of new relaxation channels due to the presence of non-vanishing bulk viscosity. We study shock wave collisions at different energies in gauge theories with different degrees of non-conformality and compare three relaxation times which can occur in different orderings: the hydrodynamization time (when hydrodynamics becomes applicable), the EoSization time (when the average pressure approaches its equilibrium value) and the condensate relaxation time (when the expectation value of a scalar operator approaches its equilibrium value). We find that these processes can occur in several different orderings. In particular, the condensate can remain far from equilibrium even long after the plasma has hydrodynamized and EoSized.
© The Authors, published by EDP Sciences, 2018
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (http://creativecommons.org/licenses/by/4.0/).