Ising 2D T’-Expansion Scheme (Ising-2DTExS)
The Ising-2DTExS module of the NSF-funded MUSES project provides a framework for constructing a family of two–dimensional equations of state (EoS) of strongly interacting matter at finite temperature \(T\) and baryon chemical potential \(\mu_B\). The EoS includes a first-order phase transition at large \(\mu_B\) and a critical point associated with the 3D Ising universality class.
The module employs the \(T'\)-Expansion Scheme (TExS), which introduces an effective temperature \(T'\). This quantity is defined as an expansion in powers of \(\mu_B/T\), where the expansion coefficients \(\kappa\) are determined from lattice QCD calculations at \(\mu_B = 0\). These coefficients are related to baryon number susceptibilities \(\chi\).
Within this framework, the location of the critical point is not predicted but can be specified by the user along a parametrized transition line. The size and shape of the critical region are also adjustable parameters. The critical behavior is incorporated by mapping thermodynamic quantities from the 3D Ising universality class onto QCD thermodynamic variables.
The module can be used to compute nuclear equations of state for temperatures in the range
and baryon chemical potentials
at vanishing electric charge and strangeness chemical potentials (\(\mu_Q = \mu_S = 0\)).