PERCOLATION AND DISORDERED SYSTEMS Geoffrey GRIMMETT
PERCOLATION AND DISORDERED SYSTEMS Geoffrey GRIMMETT
PERCOLATION AND DISORDERED SYSTEMS Geoffrey GRIMMETT
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Percolation and Disordered Systems 199<br />
B(n) 010101<br />
R<br />
00 11 00 11 01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
00 11 00 11 00 11 00 11 00 11 00 11 01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
00 11<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
010101010101<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
01<br />
Fig. 7.4. An illustration of Lemma 7.17. The hatched regions are copies of B(m)<br />
all of whose edges are p-open. The central box B(m) lies within some (dotted) region<br />
R. Some vertex in R is joined by a path to some vertex in ∂B(n), which is in turn<br />
connected to a seed lying on the surface of B(n).<br />
and the claim of the lemma follows by (7.13). �<br />
Having constructed open paths from B(m) to K(m, n), we shall need to<br />
repeat the construction, beginning instead at an appropriate seed in K(m, n).<br />
This is problematic, since we have discovered a mixture of information, some<br />
of it negative, about the immediate environs of such seeds. In order to overcome<br />
the effect of such negative information, we shall work at edge-density<br />
p + δ rather than p. In preparation, let (X(e) : e ∈ E d ) be independent random<br />
variables having the uniform distribution on [0, 1], and let ηp(e) be the<br />
indicator function that X(e) < p; recall Section 2.3. We say that e is p-open<br />
if X(e) < p and p-closed otherwise, and we denote by P the appropriate<br />
probability measure.<br />
For any subset V of Z 3 , we define the exterior boundary ∆V and exterior<br />
edge-boundary ∆eV by<br />
∆V = {x ∈ Z 3 : x �∈ V, x ∼ y for some y ∈ V },<br />
∆eV = {〈x, y〉 : x ∈ V, y ∈ ∆V, x ∼ y}.<br />
We write EV for the set of all edges of L 3 joining pairs of vertices in V .<br />
We shall make repeated use of the following lemma 5 , which is illustrated<br />
in Figure 7.4.<br />
5 This lemma is basically Lemma 6 of [164], the difference being that [164] was addressed<br />
at site percolation. R. Meester and J. Steif have kindly pointed out that, in the case of<br />
site percolation, a slightly more general lemma is required than that presented in [164].<br />
The following remarks are directed at the necessary changes to Lemma 6 of [164], and they<br />
use the notation of [164]. The proof of the more general lemma is similar to that of the<br />
original version. The domain of β is replaced by a general subset S of B(n) \ T(n), and<br />
G is the event {there exists a path in B(n) from S to K(m, n), this path being p-open in<br />
B(n) \ S and (β(u) + δ)-open at its unique vertex u ∈ S}. In applying the lemma just<br />
after (4.10) of [164], we take S = ∆C2 ∩ B(n) (and similarly later).