T. Kilpelainen et P. Lindqvist, ON THE DIRICHLET BOUNDARY-VALUE PROBLEM FOR A DEGENERATE PARABOLIC EQUATION, SIAM journal on mathematical analysis, 27(3), 1996, pp. 661-683
The Perron method for degenerate parabolic equations like u(t) = div(\
del u\(p-2)del u) is studied. The regular boundary points for the Diri
chlet problem are characterized in terms of barriers. In the particula
r case of the space-time cylinder G x (0, T), a geometric characteriza
tion in terms of a Wiener-type test is given for regularity.