Units
-----

The HRG EoS module uses megaelectronvolt (MeV) as the preferred unit for all input and output quantities. The table below contains the units used for all output quantities (if not specified, the quantity is dimensionless and has thus no unit).

+---------------------------------------------------------------+-----------------+
| **Variable**                                                  | **Unit**        |
+===============================================================+=================+
| Temperature (:math:`T`)                                       | MeV             |
+---------------------------------------------------------------+-----------------+
| Baryon chemical potential (:math:`\mu_B`)                     | MeV             |
+---------------------------------------------------------------+-----------------+
| Electric charge chemical potential (:math:`\mu_Q`)            | MeV             |
+---------------------------------------------------------------+-----------------+
| Strangeness chemical potential (:math:`\mu_S`)                | MeV             |
+---------------------------------------------------------------+-----------------+
| Pressure (:math:`P`)                                          | MeV :math:`^4`  |
+---------------------------------------------------------------+-----------------+
| Energy density (:math:`\varepsilon`)                          | MeV :math:`^4`  |
+---------------------------------------------------------------+-----------------+
| Entropy density (:math:`s`)                                   | MeV :math:`^3`  |
+---------------------------------------------------------------+-----------------+
| Baryon number density (:math:`n_B`)                           | MeV :math:`^3`  |
+---------------------------------------------------------------+-----------------+
| Electric charge density (:math:`n_Q`)                         | MeV :math:`^3`  |
+---------------------------------------------------------------+-----------------+
| Strangeness density (:math:`n_S`)                             | MeV :math:`^3`  |
+---------------------------------------------------------------+-----------------+
| Baryon susceptibility (:math:`\chi_2^B`)                      | MeV :math:`^2`  |
+---------------------------------------------------------------+-----------------+
| Strangeness susceptibility (:math:`\chi_2^S`)                 | MeV :math:`^2`  |
+---------------------------------------------------------------+-----------------+
| Charge susceptibility (:math:`\chi_2^Q`)                      | MeV :math:`^2`  |
+---------------------------------------------------------------+-----------------+
| Baryon-strangeness susceptibility (:math:`\chi_{11}^{BS}`)    | MeV :math:`^2`  |
+---------------------------------------------------------------+-----------------+
| Baryon-charge susceptibility (:math:`\chi_{11}^{BQ}`)         | MeV :math:`^2`  |
+---------------------------------------------------------------+-----------------+
| Charge-strangeness susceptibility (:math:`\chi_{11}^{QS}`)    | MeV :math:`^2`  |
+---------------------------------------------------------------+-----------------+
| T-derivative of baryon density (:math:`dn_B/dT`)              | MeV :math:`^2`  |
+---------------------------------------------------------------+-----------------+
| T-derivative of strangeness density (:math:`dn_S/dT`)         | MeV :math:`^2`  |
+---------------------------------------------------------------+-----------------+
| T-derivative of charge density (:math:`dn_Q/dT`)              | MeV :math:`^2`  |
+---------------------------------------------------------------+-----------------+
| T-derivative of entropy density (:math:`ds/dT`)               | MeV :math:`^2`  |
+---------------------------------------------------------------+-----------------+
| Squared isentropic speed of sound (:math:`c_s^2`)             | (dimensionless) |
+---------------------------------------------------------------+-----------------+
| Specific heat at constant volume (:math:`c_V`)                | MeV :math:`^3`  |
+---------------------------------------------------------------+-----------------+

In addition, the following units are used for the van der Waals interaction parameters, specified by the user in the ``HRG_parameters`` section of |config|_:

+---------------------------------------------------------------+---------------------+
| **Parameter**                                                 | **Unit**            |
+===============================================================+=====================+
| VDW attractive parameter (:math:`a`)                          | GeV·fm :math:`^3`   |
+---------------------------------------------------------------+---------------------+
| VDW (anti)baryon excluding-volume parameter (:math:`b`)       | fm :math:`^3`       |
+---------------------------------------------------------------+---------------------+
| VDW meson excluding-volume parameter (:math:`b_m`)            | fm :math:`^3`       |
+---------------------------------------------------------------+---------------------+

.. |config| replace:: **config.yaml**
.. _config: https://gitlab.com/nsf-muses/hadronic-resonance-gas/hrg-eos-module/-/blob/master/input/config.yaml?ref_type=heads