since all isotopes can essentially be treated as non-interacting ideal Boltzmann gases. Often, corrections for Coulomb interactions are included. Photons and electrons/positrons can be treated everywhere as ideal Bose and Fermi gases, respectively. Since electrons will be partially or completely degenerate, computing the electron/positron EOS involves the FLOP-intensive solution of Fermi integrals. Because of this, their EOS is often included in tabulated form.

    At temperatures above $\sim$$0.5\,\mathrm{MeV}$, nuclear statistical equilibrium holds. This greatly simplifies things, since now the electron fraction $Y_e$ (number of electrons per baryon; because of macroscopic charge neutrality, $Y_e$ is equal to $Y_p$, the number fraction of protons) is the only compositional variable. The mass fractions of all other baryonic species can be obtained by solving Saha-like equations for compositional equilibrium. At densities below $\sim$$10^{10} -
      10^{11}\,\mathrm{g\,cm}^{-3}$ the baryons can still be treated as ideal Boltzmann gases (but including Coulomb corrections).

    The nuclear force becomes relevant at densities near and above $10^{10} - 10^{11}\,\mathrm{g\,cm}^{-3}$. It is an effective quantum many-body interaction of the strong force and its detailed properties are presently not known. Under supernova conditions, matter will be in NSE in the nuclear regime and the EOS is a function of density, temperature, and $Y_e$. Starting 