Professor Ruppeiner’s theoretical research has focused on using curved space geometry to represent physical situations in which many atoms cooperate to produce a few independent average properties, i.e., those in thermodynamics.  Although the laws of thermodynamics make no reference to atoms, thermodynamics nevertheless yields information at length scales below the macroscopic through fluctuation theory.  Fluctuation theory leads to the interplay between the macroscopic and the mesoscopic, which yields much useful information.  The curved space thermodynamic information geometry is an essential tool in analyzing this interplay between the two size scales.  Professor Ruppeiner has applied these ideas to fluids, spin systems, and black holes.