Breather
= Breather
{title2=$u(x,t+P)=u(x,t)$}
A <breather> is a spatially localized nonlinear-wave solution periodic in time. It does not separate into independently traveling lumps while it breathes. A <Sine-Gordon breather> arises from a complex-conjugate soliton pair. In the quantum sine-Gordon model, the associated neutral kink-antikink bound particles are also called <breathers>.