# 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 formalism1 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

1

The formalism here is based on Mixed polytrope with density discontinuities (Christensen-Dalsgaard, 2015, unpublished), with extensions to allow for constant-density regions.