Hello, I am studing polytropes and I found something intersting here: http://astronomy.sussex.ac.uk/~pd48/Polytropes.ppt [Broken](adsbygoogle = window.adsbygoogle || []).push({});

I got a problem at slide 5 where she says that the polytropic index n is equal to 0 for a homogenous gas sphere.

I am not able to figure out why. From the polytropic equation P=K*ro^(gamma) we can write: dP/dr=k(gamma)ro^(gamma-1)d(ro)/dr

and since ro=const we can say that dP/dr=0 for any value of gamma and moreover we can say that there is no equilibrium.

thanks for help

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# Polytropic Models

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