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CATEGORIES:Isaac Newton Institute Seminar Series
SUMMARY:Collective coordinates\, asymptotics and domain wa
ll dynamics in ferromagnets - Jonathan Robbins (Un
iversity of Bristol)
DTSTART;TZID=Europe/London:20190130T170000
DTEND;TZID=Europe/London:20190130T180000
UID:TALK119587AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/119587
DESCRIPTION:*The method of collective coordinates is a simpl
e and widely used variational procedure for findin
g approximate solutions to many- or infinite-dimen
sional\, possibly damped and driven\, Hamiltonian
systems. The approximate solutions are typically c
haracterised by a small number of time-dependent p
arameters\, which are understood to describe a sma
ll number of activated modes. The simplicity of th
e method comes at a price\, however\, as it does n
ot allow a determination of how good (or bad) the
approximation is. In certain regimes\, asymptotic
expansions can provide the requisite estimates\, t
hough they require more work.* \; *Thi
s is illustrated for the problem of the motion of
domain walls in ferromagnets. Domain walls are int
erfaces between differently oriented magnetic doma
ins\, and the dynamics of these interfaces under a
pplied magnetic fields and currents is a problem o
f current physical and technological interest.*
\; *We also describe behaviour in a high
-field regime\, beyond the well-known Walker break
down\, where one of the domains becomes unstable.
A new type of dynamics emerges that appears to be&
nbsp\;beyond the reach of a collective coordinate
description. It can \;be described using \
;front propagation theory\, \;but rigorous res
ults (akin to a \;KPP analysis) appear to be c
hallenging.* \; *This is joint work wi
th Arseni Goussev\, Valeriy Slastikov\, and Sergiy
Vasylkevych.*

LOCATION:Seminar Room 2\, Newton Institute
CONTACT:info@newton.ac.uk
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