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CATEGORIES:DAMTP Statistical Physics and Soft Matter Seminar
SUMMARY:Memory effects in soft matter - Julian Kappler\, D
AMTP
DTSTART;TZID=Europe/London:20181106T130000
DTEND;TZID=Europe/London:20181106T140000
UID:TALK111319AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/111319
DESCRIPTION:In biological and other non-isolated systems\, a p
hysical process of interest is typically described
by a reaction coordinate (collective variable) th
at couples to an environment. In many cases\, an e
ffective model for the reaction coordinate is desi
red. If there is no separation of time scales betw
een the dynamics of reaction coordinate and enviro
nment\, the effective model for the reaction coord
inate is non-Markovian\, i.e. contains memory effe
cts. In this talk\, we discuss two different non-M
arkovian systems.\n\nThe rate-determining step of
a reaction is usually modeled as the crossing of a
n effective one-dimensional reaction coordinate ov
er a single barrier. In the first part of this tal
k we study the mean first-passage time for barrier
crossing for non-Markovian dynamics\, as describe
d by the generalized Langevin equation. For single
-exponential memory\, we discuss the known asympto
tic scalings\, identify a new parameter regime whe
re memory effects accelerate barrier crossing\, an
d present a heuristic formula for calculating the
mean first-passage time [1].\n\nIn the second part
of this talk we study 2D sound waves in an elasti
c interface that is coupled to a viscous bulk flui
d [2]. We first show that for small amplitudes\, s
uch waves are described by a linear fractional wav
e equation. The fractional character of the equati
on constitutes a memory effect and originates from
integrating out the bulk fluid degrees of freedom
. We then include nonlinear effects due to the dep
endence of the interface compressibility on the lo
cal compression\, and find that our nonlinear theo
ry reproduces experimental key features of surface
waves in phospholipid monolayers at the air-water
interface.\n\nReferences:\n[1] J. Kappler\, J. O.
Daldrop\, F. N. BrĂ¼nig\, M. D. Boehle\, and R. R.
Netz. "Memory-induced acceleration and slowdown o
f barrier crossing "\, The Journal of Chemical Phy
sics\, vol. 148\, p. 014903\, 2018. DOI: 10.1063/1
.4998239\n[2] J. Kappler\, S. Shrivastava\, M. F.
Schneider\, and R. R. Netz. "Nonlinear fractional
waves at elastic interfaces"\, Physical Review Flu
ids\, vol. 2\, p. 114804\, 2017. DOI: 10.1103/Phys
RevFluids.2.114804
LOCATION:MR11\, CMS
CONTACT:Etienne Fodor
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