Editing Appendix/Ramblings/ForCohlHoward (section)

===Quandary===

Because we have chosen over the past four decades to employ an explicit-FVM approach in our examination of the stability of rotating, self-gravitating fluids, we have been constrained to examine the behavior of ''compressible'' rather than ''incompressible'' fluids.  This is perfectly acceptable &#8212; and even desirable &#8212; in the context of studies of star-formation, for example, because we are confident that star-forming gas clouds and young protostars are composed of fluids that obey compressible equations of state.  But it is difficult to critique the validity &#8212; and therefore relevance &#8212; of the results of such compressible-fluid simulations because <b>the published literature contains virtually no linear-stability analyses of compressible fluid systems</b> against which our nonlinear simulations can be compared.

On the other hand, as Chandrasekhar details in [[Appendix/References#EFE|<font color="red">EFE</font>]], the literature is packed full of studies that have quantitatively assessed the relative stability of rotating, self-gravitating, ''incompressible'' fluid systems.  (And, associated with the arrival of Stephen Sorokanich at NIST, we expect this literature to expand significantly.)  So, the validity &#8212; and relevance &#8212; of our numerical simulations would be on a much firmer foundation if we had the ability to model the evolution of incompressible fluid systems.  As an additional reward, a numerical simulation tool of this type would allow us to follow the ''nonlinear'' development of instabilities (in all Riemann ellipsoids, for example) whose onset has been predicted only from ''linear'' stability analyses.