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SUMMARY:New understanding of liquid thermodynamics\, viscosity and its low
 er bounds - Kostya Trachenko ( Queen Mary\, University of London)
DTSTART:20231012T103000Z
DTEND:20231012T113000Z
UID:TALK202930@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:Understanding most basic thermodynamic properties of the liqui
 d state such as energy and heat capacity turned out to be a long-standing 
 problem in physics [1\,2]. Landau&Lifshitz textbook states that no general
  formulas can be derived for liquid thermodynamic functions because the in
 teractions are both strong and system-specific. Phrased differently\, liqu
 ids have no small parameter. Recent theoretical results open a new way to 
 understand liquid thermodynamics on the basis of collective excitations (p
 honons) as is done in the solid state theory. Differently from solids\, th
 e phase space for these excitations reduces with temperature [2\,3]\, expl
 aining the universal decrease of liquid constant-volume specific heat. I w
 ill discuss the implication of the above theory for fundamental understand
 ing of liquids. I will also explain how this picture extends above the cri
 tical point where the Frenkel line separates two physically distinct state
 s on the supercritical phase diagram [4]. I will subsequently describe how
  this leads to the theory of minimal quantum viscosity in terms of fundame
 ntal physical constants [5]. This answers the long-standing question discu
 ssed by Purcell and Weisskopf of why viscosity never drops below a certain
  value [6] and implies that water and life and well attuned to the degree 
 of quantumness of the physical world [6\,7].\n\n1. K. Trachenko\, Theory o
 f liquids: from excitations to thermodynamics (Cambridge University Press\
 , 2023)\n2. K Trachenko and V Brazhkin\, Reports on Progress in Physics 79
 \, 016502 (2016)\n3. M Baggioli\, M Vasin\, V Brazhkin and K Trachenko\, P
 hysics Reports 865\, 1 (2020)\n4. C Cockrell\, V Brazhkin and K Trachenko\
 , Physics Reports 941\, 1 (2021)\n5. K Trachenko and V Brazhkin\, Minimal 
 quantum viscosity from fundamental physical constants\, Science Adv. 6\, e
 aba3747 (2020)\n6. K Trachenko and V Brazhkin\, Physics Today 74\, 12\, 66
  (2021)\n7. K. Trachenko\, Properties of condensed matter from fundamental
  physical constants\, Advances in Physics 70\,469 (2023)\n
LOCATION:Open Plan Area\, Institute for Energy and Environmental Flows\, M
 adingley Rise CB3 0EZ
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