Parameters

The HRG equation of state module has a variety of parameters for the calculation of the equation of state. The output file will correspond to the selected parameter choices.

As described in the Quickstart, the user must provide a config.yaml file. The purpose of this file is to supply all the configuration information required to run the module, such as input data and program options. The rules for this input file are specified in the OpenAPI Specifications file provided with the module.

Each time the module is executed, it reads the config.yaml file provided by the user and verifies that the input conforms to the OpenAPI specifications. If it does not, module execution will be unsuccessful. When this happens, make sure to check the logs to identify the issue with your configuration.

It is not necessary to specify every single parameter in the configuration file. Parameters listed under the HRG_parameters and switchers sections are optional: if omitted, they will be automatically assigned the default value indicated in the OpenAPI specifications.

By contrast, all 12 grid parameters listed under the parameters section (T_min, T_max, dT, mu_B_min, mu_B_max, dmu_B, mu_Q_min, mu_Q_max, dmu_Q, mu_S_min, mu_S_max, dmu_S) are required and must always be explicitly provided in the config.yaml file; the module will fail validation if any of them is missing.

Upon successful execution, the module may produce several output files. These are described in the OpenAPI specification as part of the output schema. Not all of these files are created during every run, and some require the user to specify particular options in the config.yaml file.

Below are tables providing a brief overview of module’s input, semi-internal and output parameter files.

Input Parameters

The input parameters required to execute the HRG module are presented in the table below. All parameters have default values in case the user does not specify any. Complete details are given in the module’s OpenAPI specifications.

Category Description	Input Parameter	Description	Required	Default
Parameters	`T_min`	Minimum temperature (in MeV)	Yes	`1.0`
	`T_max`	Maximum temperature (in MeV)	Yes	`180.0`
	`dT`	Temperature step size (in MeV)	Yes	`5.0`
	`mu_B_min`	Min. baryon chem. potential (in MeV)	Yes	`0.0`
	`mu_B_max`	Max. baryon chem. potential (in MeV)	Yes	`930.0`
	`dmu_B`	Baryon chem. potential step (in MeV)	Yes	`10.0`
	`mu_Q_min`	Min. charge chem. potential (in MeV)	Yes	`0.0`
	`mu_Q_max`	Max. charge chem. potential (in MeV)	Yes	`120.0`
	`dmu_Q`	Charge chem. potential step (in MeV)	Yes	`10.0`
	`mu_S_min`	Min. strangeness chem. pot. (in MeV)	Yes	`0.0`
	`mu_S_max`	Max. strangeness chem. pot. (in MeV)	Yes	`490.0`
	`dmu_S`	Strangeness chem. pot. step (in MeV)	Yes	`10.0`
HRG_Parameters	`a`	VdW attractive param. (in GeV·fm³)	No	`0.329`
	`b`	VdW baryon excl.-vol. param. (in fm³)	No	`3.42`
	`bm`	VdW meson excl.-vol. param. (in fm³)	No	`0.0`
	`particle_list`	Particle list to be used for HRG calculations	No	`/Thermal-FIST/input/list/PDG2025/list.dat`
	`interacting-pions`	Switcher for interacting pions model	No	`False`
Switchers	`get_P`	Store pressure \(p\)	No	`True`
	`get_E_dens`	Store energy density	No	`True`
	`get_s_dens`	Store entropy density	No	`True`
	`get_B_dens`	Store baryon number density	No	`True`
	`get_Q_dens`	Store charge number density	No	`True`
	`get_S_dens`	Store strangeness number density	No	`True`
	`get_PressHessianMatrix`	Store elements of the pressure Hessian matrix	No	`False`

Following is an example of an exhaustive config.yaml file for the HRG module:

HRG_parameters:
   a: 0.329
   b: 3.42
   bm: 0.1
   interacting-pions: true
   particle_list: /Thermal-FIST/input/list/PDG2025/list.dat
parameters:
   T_min: 0.0
   T_max: 150.0
   dT: 75.0
   mu_B_min: 0.0
   mu_B_max: 300.0
   dmu_B: 300.0
   mu_Q_min: 0.0
   mu_Q_max: 100.0
   dmu_Q: 100.0
   mu_S_min: 0.0
   mu_S_max: 200.0
   dmu_S: 200.0
switchers:
   get_P: true
   get_E_dens: true
   get_s_dens: true
   get_B_dens: true
   get_Q_dens: true
   get_S_dens: true
   get_PressHessianMatrix: true

Semi-internal variables

Several particle lists are available for the HRG calculations, and can be selected by the user through the particle_list parameter in the HRG_parameters section of the config.yaml file. If not specified, the default particle list is the PDG2025 list (as shown in the parameters summary table above), which includes all hadrons and resonances listed in the Particle Data Group (PDG) tables as of 2025. This list is located in the Thermal-FIST package at /Thermal-FIST/input/list/PDG2025/list.dat.

However, the user is free to select another of the different particle lists available in the /Thermal-FIST/input/list/ folder, as well as providing their own, as long as it is in the correct format. The format of the particle list files is described in the Thermal-FIST documentation, and typically includes information such as particle ID, mass, degeneracy, quantum numbers, and decay width.

Output Parameters

The output files generated by the module are in .csv format, and are stored in the output/ directory.

HRG_output_thermodynamics.csv: this file contains values for thermodynamic observables such as pressure, energy density, charge densities, entropy density, as a function of temperature \(T\) and the conserved charge chemical potentials, i.e. \(\mu_B\), \(\mu_S\) and \(\mu_Q\).

HRG_metadata_thermodynamics.yaml: this file contains the metadata for the thermodynamic output file, describing the structure, types and units of the data.

status.yaml: Provides the status of the module’s execution, including success or error messages.