  Ultracentral heavy ion collisions due to their exceptionally large
multiplicity probe an interesting regime of quark-gluon plasma where the size
is (mostly) fixed and fluctuations in the initial condition dominate. Spurred
by the recent measurement of the CMS collaboration we investigate the driving
factors of the increase of transverse momentum, including a complete analysis
of the influence of the QCD equation of state. Particularly interesting is the
influence of the centrality selection as well as the initial energy deposition.
