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.