Cactus Code Thorn EOS_Polytrope
Author(s)    : Ian Hawke
               Frank Löffler
Maintainer(s): Cactus team
Licence      : LGPL
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1. Purpose

This is a "faked" polytropic equation of state. It is designed to work
through the CactusEOS interface.
The EoS reads Pressure = eos_k * rho ** (eos_gamma). The specific internal
energy is given by the assumption of a perfect fluid.