R. D. Benguria and M. C. Depassier, P. U. Catolica de Chile
 Variational Characterization of the Speed of Propagation of
        Fronts for the Nonlinear Diffusion Equation
(12K, LATEX)

ABSTRACT.  We give a variational characterization for the speed of fronts
of the nonlinear diffusion equation $u_t = u_{xx} + f(u)$ with
$f>0$, which permits the  calculation of  the exact speed for
arbitrary $f$.