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SUMMARY:New understanding of liquid thermodynamics\, viscosity and its low
 er bounds - Kostya Trachenko ( Queen Mary\, University of London)
DTSTART:20240314T113000Z
DTEND:20240314T123000Z
UID:TALK212173@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:Theories of gases and solids are well developed and date back 
 100-150 years ago. In contrast\, understanding most basic thermodynamic pr
 operties (eg energy and heat capacity) of the third state of matter - the 
 liquid state - turned out to be a long-standing problem in physics [1]. La
 ndau&Lifshitz textbook states that no general formulas can be derived for 
 liquid thermodynamic functions because the interactions are both strong an
 d system-specific. Phrased aptly by Pitaevskii\, liquids have no small par
 ameter.\n\nRecent theoretical results open a new way to understand liquid 
 thermodynamics on the basis of collective excitations (phonons) as is done
  in the solid state theory. Differently from solids\, the number of phonon
 s is variable in liquids and decreases with temperature [1\,2]. This effec
 t is quantified in a phonon theory of liquid thermodynamics and explains t
 he universal decrease of liquid constant-volume specific heat with tempera
 ture. One implication of this theory is that liquids can now be consistent
 ly understood on par with solids and are no longer “Cinderella of Physic
 s” as believed until recently. I will also explain how this picture exte
 nds above the critical point where the Frenkel line separates two physical
 ly distinct states on the supercritical phase diagram [3].\n\nI will subse
 quently describe how this picture leads to the theory of minimal quantum v
 iscosity in terms of fundamental physical constants including the Planck c
 onstant [4]. This answers the long-standing question discussed by Purcell 
 and Weisskopf of why viscosity never drops below a certain value [5]. This
  also means that water and life and well attuned to the degree of quantumn
 ess of the physical world [5].  This\, in turn\, implies\, that we can bet
 ter understand fundamental physical constants from biological and life pro
 cesses [6].\n\n1. K Trachenko\, Theory of liquids: from excitation to ther
 modynamics (Cambridge University Press\, 2023)\; K Trachenko and V Brazhki
 n\, Reports on Progress in Physics 2016\n2. M Baggioli\, M Vasin\, V Brazh
 kin and K Trachenko\, Physics Reports 2020\n3. C Cockrell\, V Brazhkin and
  K Trachenko\, Physics Reports 2021\n4. K Trachenko and V Brazhkin\, Minim
 al quantum viscosity from fundamental physical constants\, Science Advance
 s 2020\; K Trachenko\, Properties of condensed matter from fundamental phy
 sical constants\, Advances in Physics (2023)\n5. K Trachenko and V Brazhki
 n\, Physics Today 74\, 12\, 66 (2021)\n6. K Trachenko\, Constraints on fun
 damental constants from bio-friendly viscosity and diffusion\, Science Adv
 ances 2023
LOCATION:Open Plan Area\, Institute for Energy and Environmental Flows\, M
 adingley Rise CB3 0EZ
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