  A very interesting recent paper by Dalvi et al. has demonstrated convincingly
with adhesion experiments of a soft material with a hard rough material that
the simple energy idea of Persson and Tosatti works reasonably well, namely the
reduction in apparent work of adhesion is equal to the energy required to
achieve conformal contact. We demonstrate here that, in terms of a stickiness
criterion, this is extremely close to a criterion we derive from BAM (Bearing
Area Model) of Ciavarella, and not very far from that of Violano et al. It is
rather surprising that all these criteria give very close results and this also
confirms stickiness to be mainly dependent on macroscopic quantities.
