Jeans Mass and the
Growth of Perturbations
•Starting point is standard equations of gas dynamics in a gravitational field (from Longair, same starting point in Combes et al. – both texts useful):
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•We have gas with pressure, density, and a velocity distribution v (u in Combes), in a gravitational potential.  This is written for Eulerian coordinates (fixed in space).  Can write in Lagrangian coordinates that follow fluid elements.  Note, this is non-relativistic which is fine for an introduction.
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