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SUMMARY:Sine-Gordon kinks and dislocation motion - Steven Fitzgerald\, Dep
 artment of Materials Science\, University of Oxford
DTSTART:20151105T160000Z
DTEND:20151105T170000Z
UID:TALK60232@talks.cam.ac.uk
CONTACT:Stephen Walley
DESCRIPTION:Under moderate applied stresses\, dislocations move through th
 e periodic Peierls potential via the thermal nucleation of kink pairs. The
  nucleation rate\, and hence the dislocation velocity\, is an extremely no
 nlinear function of the applied stress and temperature. Previous theoretic
 al calculations of the rate either involve computer simulations at the ato
 mic scale (which are too computationally demanding for modelling plasticit
 y) or produce approximate formulae (valid only for small or large applied 
 forces). In this talk I will derive a simple\, general\, and exact formula
  for the rate\, directly from the stochastic equation of motion for the di
 slocation\, using methods drawn from quantum field theory. This formula fi
 ts experimental and numerical data very well\, and also applies to the man
 y other physical systems modelled by elastic strings interacting with peri
 odic potentials. 
LOCATION:Mott Seminar Room\, Cavendish Laboratory
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