We consider the parabolic one-dimensional Allen–Cahn equation
![](//static-cambridge-org.ezproxyberklee.flo.org/content/id/urn%3Acambridge.org%3Aid%3Aarticle%3AS0308210517000245/resource/name/S0308210517000245_eqn01.gif?pub-status=live)
The steady state
connects, as a ‘transition layer’, the stable phases –1 and +1. We construct a solution u with any given number k of transition layers between –1 and +1. Mainly they consist of k time-travelling copies of w, with each interface diverging as t → –∞. More precisely, we find
![](//static-cambridge-org.ezproxyberklee.flo.org/content/id/urn%3Acambridge.org%3Aid%3Aarticle%3AS0308210517000245/resource/name/S0308210517000245_eqn02.gif?pub-status=live)
where the functions ξj (t) satisfy a first-order Toda-type system. They are given by
![](//static-cambridge-org.ezproxyberklee.flo.org/content/id/urn%3Acambridge.org%3Aid%3Aarticle%3AS0308210517000245/resource/name/S0308210517000245_eqn03.gif?pub-status=live)
for certain explicit constants γjk.