# Figure 9

 The ratio $v_{4}\{2, |\Delta\eta| > 0.8\} / v_{4}[2, |\Delta\eta| > 0.8]$ in Pb--Pb collisions at $\sqrt{s_{_{\rm NN}}} = 2.76$~TeV. The different panels show the centrality evolution of the measurements. Hydrodynamic calculations with MC-Glauber initial conditions and $\eta/s =$ 0.08~ and with MC-KLN initial conditions and $\eta/s =$ 0.20~, with Trento initial conditions and temperature dependent $\eta/s$~ and AMPT initial conditions and $\eta/s =$ 0.08~ are shown in green dot-dash, orange dashed curves, and magenta and grey shaded areas, respectively.