Solitons=Only waves?? given any wave equation (linear or not) could we always find a solution. [tex] \Psi (x,t)= f(x-ct) [/tex] is this the so-called only wave or soliton ?? , and what would be the shape of f(r) r=x-ct given a certain wave equation ?.. does the Schröedinguer equation admit such solutions or only if this SE is non-linear ??