Polytrope

Solution of the Lane-Emden pressure-density equation for astrophysical bodies

In astrophysics, a polytrope refers to a solution of the Lane–Emden equation in which the pressure depends upon the density in the form where P is pressure, ρ is density and K is a constant of proportionality. The constant n is known as the polytropic index; note however that the polytropic index has an alternative definition as with n as the exponent.

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