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SUMMARY:The second law of thermodynamics and its mesoscopic interpretation
  - Professor Mike Cates (DAMTP)
DTSTART:20250123T140000Z
DTEND:20250123T150000Z
UID:TALK225757@talks.cam.ac.uk
CONTACT:Gaurav
DESCRIPTION:This talk is partly historical overview\, partly a discussion 
 of how different 'interpretations' of entropy give wildly different experi
 mental predictions\, and partly an account of the stochastic interpretatio
 n of the second law and its role in current research on active soft matter
 . The talk was originally prepared for an event marking the 200th Annivers
 ary of Kelvin's birth\, June 26th 1824.\n\nKelvin's statement of the secon
 d law was grounded in the macroscopic world of heat engines. It led to the
  thermodynamic concept of entropy -- the second law being equivalent to a 
 statement that the entropy in a closed system (or indeed\, the universe) c
 an only increase. This 'universal principle of degradation' applies only a
 t macroscopic scales\, as Kelvin made clear in 1874. In the intervening 15
 0 years\, work on mesoscopic systems\, specifically colloidal suspensions\
 , has led to crucial clarifications and extensions of the second law.  The
  first instance was Perrin's 1909 confirmation via colloidal sedimentation
  of Boltzmann's statistical view of entropy (and with it the atomic theory
  of matter). Much later\, the discovery in 1986 of colloidal crystals offe
 rs overlooked but decisive evidence that the statistical entropy is inform
 atic rather than kinetic in character. Third\, colloidal experiments were 
 the first to confirm several powerful generalizations of the second law (f
 ormulated in the 1990s) known as 'fluctuation theorems'. These quantify pr
 ecisely how probable it is for entropy to decrease spontaneously 'against 
 the odds'. Finally\, in the 21st Century\, colloid scientists have turned 
 their attention to self-propelled particles whose dynamics are irreversibl
 e at the smallest scales measurable. These 'active matter' systems create 
 a new arena in which concepts such as entropy production can be explored a
 t the mesoscale.
LOCATION:TCM Seminar Room
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