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Colloquium: George Ruppeiner

Wednesday, October 12, 2016
3:30 PM - 4:30 PM
Physics : 401
TITLE: From fluids to black holes: thermodynamics probes the mesoscale

ABSTRACT:
A number of thermodynamic properties originate from mesoscopic structures of size in between the microscopic and the macroscopic.  To understand the mesoscopic regime is thus frequently important.  However, this regime is usually difficult to address theoretically.  I propose that thermodynamic fluctuation theory, augmented by ideas from geometry of thermodynamics, can help fill this theoretical void.  Specifically, I propose that the thermodynamic curvature scalar R is a direct thermodynamic measure of intermolecular interactions.  R is positive for systems with primarily repulsive interactions, and negative for systems with primarily attractive interactions.  |R| gives the size of essential mesoscopic structures; near the critical point, |R| is the correlation length.  I discuss the theoretical contribution of R in the context of several physical situations: spin systems, exactly solvable models in statistical mechanics, real fluids in the context of possible solid-like liquid structures (including water under ambient conditions), the critical point, black hole thermodynamics, and strongly interacting Fermi systems.  An element of my discussion is a method for evaluating the thermodynamic properties of difficult strongly interacting systems directly from the interplay between the mesoscopic and the macroscopic.