Hirota tau function
= Hirota tau function
{c}
{title2=$\tau$}
An auxiliary function used in <Hirota's bilinear method> to encode a solution of an <integrable partial differential equation>. Products and ratios of tau functions replace nonlinear field variables; their differential equations become bilinear. In a <Sine-Gordon multisoliton tau representation>, two real tau functions encode the field as a continuous $4\arg(f+ig)$.