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Equations of State (EoS)

StructureSolver.jl provides multiple EoS backends behind a common interface.

Implementations

  • PWP_EoS: piecewise polytrope (with built-in named low/high segments).
  • Polytropic_EoS: simple polytrope.
  • Table_EoS: tabulated EoS (default stable implementation).
  • Table_EoS_Hermite: experimental Hermite-based tabulated EoS (not the default).

Core interface

The main helpers are

  • get_pressure, get_density, get_number_density
  • get_energy_density, get_specific_enthalpy, get_internal_energy
  • get_sound_velocity

Most methods accept a from keyword (e.g. from=:density or from=:pressure).

Example (pressure from density):

using StructureSolver

eos = PWP_EoS(low_eos=:SLy, high_eos=:MPA1)

ρ = 1e15
p = get_pressure(eos, ρ, from=:density)

Example (density from pressure):

using StructureSolver

eos = Polytropic_EoS(K=1e5, Γ=2.0)

p = 1e34
ρ = get_density(eos, p, from=:pressure)

Units

Where relevant, the package uses CGS conventions:

  • density $\rho$ in g/cm^3
  • pressure $p$ in dyn/cm^2
  • energy density $\epsilon$ in erg/cm^3
  • sound speed $c_s$ in cm/s

If an EoS supports additional unit systems, helpers typically expose a units keyword.

Tip: when you are mixing different EoS backends in one project, keep an eye on the units keyword and always document what your input arrays represent.

Tabulated EoS

Table_EoS(:NAME) loads a built-in tabulated EoS by name (see the package data). This is the default stable implementation.

Table_EoS_Hermite is experimental and not used by default.

Maximum pressure helper

find_max_pressure(eos) can be useful for validating tabulated or piecewise models and setting scan ranges.