Holographic equation of state at finite strangeness using Bayesian analysis.

The equation of state of quantum chromodynamics (QCD), the fundamental theory of the strong interaction, at a large imbalance of quarks over antiquarks is not known from first principles. Effective models have to be used to explore different regimes of the phase diagram. We used the open-source MUSES holographic module where we employ the gauge/gravity correspondence to explore the QCD equation of state in the presence of a large strangeness chemical potential. This conjectured correspondence relates a theory of gravity in d+1 dimensions in an asymptotic anti-de Sitter geometry, to a quantum field theory in d dimensions in flat spacetime. Our description is based on a Einstein-Maxwell-dilaton action, where the gravitational theory is complemented by a scalar dilaton field and a vector Maxwell field, with couplings chosen so that black-holes in 5 dimensions can mimic QCD thermodynamics. Bayesian inference is used to determine the posterior probability distribution for parameters of the model, when constrained by first-principles Lattice QCD results. By searching for a critical endpoint of the QCD phase transition in samples of the posterior, we find evidence for a critical endpoint around a temperature and a strangeness chemical potential of T = 76 MeV and µS = 536 MeV, respectively. The strangeness critical point is at slightly lower temperatures than that at finite baryon densities.