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1. New 4D lattice QCD equation of state: Extended density coverage from a generalized $T^{\prime }$ expansion

   https://doi.org/10.1103/2dmh-26yh  

   Abuali, Ahmed; Borsányi, Szabolcs; Fodor, Zoltán; Jahan, Johannes; Kahangirwe, Micheal; Parotto, Paolo; Pásztor, Attila; Ratti, Claudia; Shah, Hitansh; Trabulsi, Seth A (September 2025, Physical Review D)

   We present a new equation of state for QCD in which the temperature $T$and the three chemical potentials for baryon number ${\mu }_B$, electric charge ${\mu }_Q$, and strangeness ${\mu }_S$can be varied independently. This result is based on a generalization of the $T^{\prime }$expansion scheme, thanks to which the diagonal ${\mu }_B$extrapolation was pushed up to a baryo-chemical potential ${\mu }_B/T\sim 3.5$for the first time. This considerably extended the coverage of the Taylor expansion, limited to ${\mu }_B/T<2.5–3$. As a consequence, we are able to offer a substantially larger coverage of the four-dimensional QCD phase diagram as well, compared to previously available Taylor expansion results. Our findings are based on new continuum estimated lattice data on the full set of second- and fourth-order fluctuations. 

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2. Finite chemical potential equation of state for QCD from an alternative expansion scheme

   https://doi.org/10.1051/epjconf/202225910015  

   Parotto, Paolo; Borsányi, Szabolcs; Fodor, Zoltan; Guenther, Jana N.; Kara, Ruben; Katz, Sandor D.; Pásztor, Attila; Ratti, Claudia; Szabó, Kalman K. (January 2022, EPJ Web of Conferences)

   David, G.; Garg, P.; Kalweit, A.; Mukherjee, S.; Ullrich, T.; Xu, Z.; Yoo, I.-K. (Ed.)

   The Taylor expansion approach to the equation of state of QCD at finite chemical potential struggles to reach large chemical potential μ B . This is primarily due to the intrinsic diffculty in precisely determining higher order Taylor coefficients, as well as the structure of the temperature dependence of such observables. In these proceedings, we illustrate a novel scheme [1] that allows us to extrapolate the equation of state of QCD without suffering from the poor convergence typical of the Taylor expansion approach. We continuum extrapolate the coefficients of our new expansion scheme and show the thermodynamic observables up to μ B / T ≤ 3.5. 

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3. Calculating QCD Phase Diagram Trajectories of Nuclear Collisions using a Semi-analytical Model

   https://doi.org/10.1051/epjconf/202327601012  

   Mendenhall, Todd; Lin, Zi-Wei (January 2023, EPJ Web of Conferences)

   Kim, Y.; Moon, D.H. (Ed.)

   At low to moderate collision energies where the parton formation time τ F is not small compared to the nuclear crossing time, the finite nuclear thickness significantly affects the energy density ϵ( t ) and net conserved-charge densities such as the net-baryon density n B ( t ) produced in heavy ion collisions. As a result, at low to moderate energies the trajectory in the QCD phase diagram is also affected by the finite nuclear thickness. Here, we first discuss our semi-analytical model and its results on ϵ( f ), n R ( t ), n Q ( t ), and n s ( t ) in central Au+Au collisions. We then compare the T ( t ), μ B ( t ), μ Q ( t ), and μ S ( t ) extracted with the ideal gas equation of state (EoS) with quantum statistics to those extracted with a lattice QCD-based EoS. We also compare the T -μ B trajectories with the RHIC chemical freezeout data. Finally, we discuss the effect of transverse flow on the trajectories. 

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4. Lattice-based equation of state with 3D ising critical point

   https://doi.org/10.1051/epjconf/202429614013  

   Kahangirwe, Micheal; Bass, Steffen A; Jahan, Johannes; Moreau, Pierre; Parotto, Paolo; Ratti, Claudia; Soloveva, Olga; Stephanov, Misha; Bratkovskaya, Elena (January 2024, EPJ Web of Conferences)

   Bellwied, R; Geurts, F; Rapp, R; Ratti, C; Timmins, A; Vitev, I (Ed.)

   The BEST Collaboration equation of state combining lattice data with the 3D Ising critical point encounters limitations due to the truncated Taylor expansion up toμ_B/T~ 2.5. This truncation consequently restricts its applicability at high densities. Through a resummation scheme, the lattice results have been extended toμ_B/T= 3.5. In this article, we amalgamate these ideas with the 3D-Ising model, yielding a family of equations of state valid up toμ_B= 700MeV with the correct critical behavior. Our equations of state feature tunable parameters, providing a stable and causal framework-a crucial tool for hydrodynamics simulations. 

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5. Lattice QCD equation of state at finite chemical potential from an alternative resummation: Strangeness neutrality and beyond

   https://doi.org/10.1051/epjconf/202327601014  

   Parotto, Paolo; Borsányi, Szabolcs; Fodor, Zoltan; Guenther, Jana N.; Kara, Ruben; Pásztor, Attila; Ratti, Claudia; Szabó, Kalman K. (January 2023, EPJ Web of Conferences)

   Kim, Y.; Moon, D.H. (Ed.)

   In this contribution we present a resummation of the Quantum Chromodynamics (QCD) equation of state from lattice simulations at imaginary chemical potentials. We generalize the scheme introduced in a previous work [1], to the case of non-zero strangeness chemical potential. We present continuum extrapolated results for thermodynamic observables in the temperature range 130MeV ≤ T ≤ 280 MeV, for chemical potentials up to μ B / T = 3:5, along the strangeness neutral line. Furthermore, we relax the constraint of strangeness neutrality, by extrapolating to small values of the strangeness-to-baryon-number ratio R = n S / n B . 

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