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Studying the QCD phase diagram using pressure derivatives from lattice QCD

Sipaz Sharma

Abstract

We summarize the application of derivatives of the QCD pressure, calculated within the framework of lattice QCD, in constructing observables that probe aspects of the QCD phase diagram at physical quark masses. We outline how the behavior of energy-like and magnetization-like observables at physical quark masses is influenced by the $(2+1)$-flavor chiral phase transition. We describe features of the chiral crossover at vanishing and non-vanishing chemical potentials and discuss deconfinement at zero chemical potential. We address the relevance of the convergence properties of the Taylor expansion of the QCD pressure in the search for the QCD critical endpoint.

Studying the QCD phase diagram using pressure derivatives from lattice QCD

Abstract

We summarize the application of derivatives of the QCD pressure, calculated within the framework of lattice QCD, in constructing observables that probe aspects of the QCD phase diagram at physical quark masses. We outline how the behavior of energy-like and magnetization-like observables at physical quark masses is influenced by the -flavor chiral phase transition. We describe features of the chiral crossover at vanishing and non-vanishing chemical potentials and discuss deconfinement at zero chemical potential. We address the relevance of the convergence properties of the Taylor expansion of the QCD pressure in the search for the QCD critical endpoint.
Paper Structure (5 sections, 16 equations, 5 figures)

This paper contains 5 sections, 16 equations, 5 figures.

Table of Contents

  1. Introduction
  2. Universal scaling framework applied to the Taylor expansion coefficients of the pressure
  3. Chiral crossover and deconfinement
  4. Taylor expansions of thermodynamic quantities and the QCD critical endpoint
  5. Conclusions

Figures (5)

  • Figure 1: Sketch of the QCD phase diagram taken from Ref. Karsch:2019mbv. The backward plane is most relevant for this article as it represents the physical light quark mass.
  • Figure 2: Shown are the Taylor expansion coefficients of the QCD pressure defined in Eq.\ref{['eq:6']} for the strangeness neutral and isospin-symmetric matter. The figures are taken from Ref. Bollweg:2022fqq.
  • Figure 3: Shown is the comparison of the pseudocritical phase boundary obtained from the lattice QCD calculations and the freeze-out parameters obtained by the experiments. The figure is taken from Ref. HotQCD:2018pds.
  • Figure 4: Shown are the relative contributins of charm quark-like excitaions $P_q^{C}$, charmed baryons, $P_B^C$, and charmed mesons, $P_M^C$ to the partial charm pressure, $P_C$. The dashed lines of the same color represent the corresponding HRG predictions. The yellow band represents $T_{pc}$ with its uncertainty. The figure is taken from Ref. Bazavov:2023xzm.
  • Figure 5: [ Right] The figure maps the pole structure of the [4,4] Padé approximant expressed in terms of two Taylor expansion parameters in Eq. \ref{['eq:pade']}. [ Left] The figure shows the location of lattice results at various temperatures in the pole map. The figures are taken from Ref. Bollweg:2022rps.