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SUMMARY:Memory effects in soft matter - Julian Kappler\, DAMTP
DTSTART:20181106T130000Z
DTEND:20181106T140000Z
UID:TALK111319@talks.cam.ac.uk
CONTACT:Etienne Fodor
DESCRIPTION:In biological and other non-isolated systems\, a physical proc
 ess of interest is typically described by a reaction coordinate (collectiv
 e variable) that couples to an environment. In many cases\, an effective m
 odel for the reaction coordinate is desired. If there is no separation of 
 time scales between the dynamics of reaction coordinate and environment\, 
 the effective model for the reaction coordinate is non-Markovian\, i.e. co
 ntains memory effects. In this talk\, we discuss two different non-Markovi
 an systems.\n\nThe rate-determining step of a reaction is usually modeled 
 as the crossing of an effective one-dimensional reaction coordinate over a
  single barrier. In the first part of this talk we study the mean first-pa
 ssage time for barrier crossing for non-Markovian dynamics\, as described 
 by the generalized Langevin equation. For single-exponential memory\, we d
 iscuss the known asymptotic scalings\, identify a new parameter regime whe
 re memory effects accelerate barrier crossing\, and present a heuristic fo
 rmula for calculating the mean first-passage time [1].\n\nIn the second pa
 rt of this talk we study 2D sound waves in an elastic interface that is co
 upled to a viscous bulk fluid [2]. We first show that for small amplitudes
 \, such waves are described by a linear fractional wave equation. The frac
 tional character of the equation constitutes a memory effect and originate
 s from integrating out the bulk fluid degrees of freedom. We then include 
 nonlinear effects due to the dependence of the interface compressibility o
 n the local compression\, and find that our nonlinear theory reproduces ex
 perimental key features of surface waves in phospholipid monolayers at the
  air-water interface.\n\nReferences:\n[1] J. Kappler\, J. O. Daldrop\, F. 
 N. Brünig\, M. D. Boehle\, and R. R. Netz. "Memory-induced acceleration a
 nd slowdown of barrier crossing "\, The Journal of Chemical Physics\, vol.
  148\, p. 014903\, 2018. DOI: 10.1063/1.4998239\n[2] J. Kappler\, S. Shriv
 astava\, M. F. Schneider\, and R. R. Netz. "Nonlinear fractional waves at 
 elastic interfaces"\, Physical Review Fluids\, vol. 2\, p. 114804\, 2017. 
 DOI: 10.1103/PhysRevFluids.2.114804
LOCATION:MR11\, CMS
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