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PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-1579
DTSTART:20091022T150000Z
DURATION:PT1H0M0S
DTSTAMP:20260422T032114Z
LAST-MODIFIED:20091009T135227Z
LOCATION:5310 Chamberlin
SUMMARY:Fluctuations\, Response\, Entropy\, and "Temperature" in Granu
 lar Packings\, R. G. Herb Condensed Matter Seminar\, Bulbul Chakrabort
 y\, Brandeis University
DESCRIPTION:To understand the mechanical response of granular material
 s\, one needs a theoretical approach that can bridge the gap between m
 icroscopic\, grain-level quantities and macroscopic\, collective prope
 rties. Fluctuations are inherently related to the number of microscopi
 c states available under a given set of macroscopic parameters. In equ
 ilibrium thermodynamics\, the microcanonical entropy\, or its derivati
 ves in other ensembles\, is the measure used to calculate fluctuations
  and response.  In disordered systems such as spin glasses\, the conce
 pt of complexity has been used to understand collective properties.  I
 n mean-field models\, free-energy minima are separated by barriers tha
 t diverge in the thermodynamic limit\, and one can in principle count 
 the number of states unambiguously.  Can we identify a physical variab
 le in granular materials that is conserved under any local dynamics\, 
 and therefore leads to a definition of complexity? For mechanically st
 able packings\, there is a topological conservation law that allows us
  to define the analog of complexity.  In this talk\, I will describe a
  framework for calculating stress fluctuations in frictional and frict
 ionless granular packings\, based on a model calculation of complexity
 \, and compare the predictions of our theory to experiments and simula
 tions.
URL:https://www.physics.wisc.edu/events/?id=1579
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