Speaker
Description
The quantum chromodynamics (QCD) equation of state (EoS) at finite temperature
and density is of fundamental importance for the characterization of hot and
dense, strongly interacting matter created in heavy ion collision experiments.
It also has important applications in hydrodynamic simulations and
the EoS of the early universe.
Strongly interacting dense matter created in experiments expands along
trajectories of fixed $s/n_B$. Based on high statistics data generated by
the HotQCD Collaboration we will determine these trajectories in the
$(T,\mu_B)$-plane using a Taylor series of the pressure of (2+1)-flavor QCD
for several values of $s/n_B$ and for thermal conditions met in heavy ion
collisions. We compare these trajectories for fixed $s/n_B$ with high
temperature perturbation theory and the hadron resonance gas model(QMHRG2020)
at low temperatures. On these trajectories we determine bulk thermodynamic
observables, e.g.net baryon number, energy, and entropy densities.
Earlier, we had shown that the pressure series is reliable up to
$\mu_B / T \le 2.5$ and Taylor expansion results are consistent with Pade
resummed series approximants. We show that this also is the case for energy
and entropy density expansions and their corresponding Pade approximants.
We find that the latter seems to be more efficient in smoothening
wiggles that arise from the strong $T$-dependence of higher order expansion
coefficients. We therefore use the Pade approximants to calculate also
observables involving higher order $T$-derivatives such as the specific
heat, speed of sound and the adiabatic compressibility of strongly interacting
matter.
