# Composite Polytropes

Composite polytropes are an extension of standard polytrope
models for stellar structure, to allow for discontinuities in the
density \(\rho\) and/or the polytropic index \(n\). This
appendix lays out the mathematical formalism[1]
underpinning them; it is intended to complement the Building POLY Models
appendix, which describes how composite polytrope models can be built
using the **build_poly** executable.

Footnotes