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SUMMARY:Diffusion in periodic porous media:  the large deviation regime
DTSTART:20190527T100000
DTSTAMP:20260511T105435Z
UID:bed2cd9df2aacc7bb498a39a1c87cc93d87f3d5ce147bde0be47a12f
CATEGORIES:Conferences - Seminars
DESCRIPTION:Alexandra Tzella\nWe consider diffusion of a tracer released s
 uddenly inside a porous medium composed of a periodic array of impenetrabl
 e circular obstacles. Classical homogenisation theory has for long establi
 shed that at large times $t\\gg 1$\, the evolution of the concentration ma
 y be approximated by a Gaussian approximation parameterised by an effectiv
 e diffusivity. This approximation is however only valid at $O(t^{1/2})$ di
 stances from the centre of mass. We develop a large-deviation approximatio
 n for the concentration that remains valid at large distances $O(t)$ from 
 the centre of mass. We provide reduced descriptions for the concentration 
 in the limiting cases of dilute and densely packed arrays as a function of
  the ratio of the gap width to the period which agree with finite-element 
 simulations. These demonstrate that a  Gaussian approximation is appropri
 ate in the dilute limit. However\, the difference between the two approxim
 ations is large in the densely packed limit. 
LOCATION:BSP 727 https://plan.epfl.ch/?room==BSP%20727
STATUS:CONFIRMED
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