UDPHIR 95/05/GG
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Title: DISCONTINUOUS INTERFACE DEPINNING FROM A ROUGH WALL
Authors: G. Giugliarelli and A.L. Stella
Comment: 9 postscript pages, Figures included, Typeset using REVTeX
Abstract:
Depinning of an interface from a random self--affine substrate with
roughness exponent $\zeta_S$ is studied in systems with short--range
interactions. In 2$D$ transfer matrix results show that for
$\zeta_S<1/2$ depinning falls in the universality class of the flat
case. When $\zeta_S$ exceeds the roughness ($\zeta_0=1/2$) of the
interface in the bulk, geometrical disorder becomes relevant and,
moreover, depinning becomes \underline{discontinuous}. The same
unexpected scenario, and a precise location of the associated
tricritical point, are obtained for a simplified hierarchical model.
It is inferred that, in 3$D$, with $\zeta_0=0$, depinning turns
first--order already for $\zeta_S>0$. Thus critical wetting may be
impossible to observe on rough substrates.