222 <strong>Geoffrey</strong> Grimmett The infra-red bound emerges in the proof of (c), of which there follows an extremely brief account. We write x ⇔ y, and say that x is ‘doubly connected’ to y, if there exist two edge-disjoint open paths from x to y. We express τp(0, x) in terms of the ‘doubly connected’ probabilities δp(u, v) = Pp(u ⇔ v). In doing so, we encounter formulae involving convolutions, which may be treated by taking transforms. At the first stage, we have that � � {0 ↔ x} = {0 ⇔ x} ∪ 〈u,v〉 � 0 ⇔ (u, v) ↔ x � � where � 0 ⇔ (u, v) ↔ x � represents the event that 〈u, v〉 is the ‘first pivotal edge’ for the event {0 ↔ x}, and that 0 is doubly connected to u. (Similar but more complicated events appear throughout the proof.) Therefore (8.27) τp(0, x) = δp(0, x) + � 〈u,v〉 Now, with A(0, u; v, x) = {v ↔ x off C 〈u,v〉(0)}, � � Pp 0 ⇔ (u, v) ↔ x . � � Pp 0 ⇔ (u, v) ↔ x � � = pPp 0 ⇔ u, A(0, u; v, x) � � � = pδp(0, u)τp(v, x) − pEp 1 {0⇔u} τp(v, x) − 1A(0,u;v,x) � whence, by (8.27), (8.28) τp(0, x) = δp(0, x) + δp ⋆ (pI) ⋆ τp(x) − Rp,0(0, x) where ⋆ denotes convolution, I is the nearest-neighbour function I(u, v) = 1 if and only if u ∼ v, and Rp,0 is a remainder. Equation (8.28) is the first step of the lace expansion, In the second step, the remainder Rp,0 is expanded similarly, and so on. Such further expansions yield the lace expansion: if p < pc then (8.29) τp(0, x) = hp,N(0, x) + hp,N ⋆ (pI) ⋆ τp(x) + (−1) N+1 Rp,N(0, x) for appropriate remainders Rp,N, and where hp,N(0, x) = δp(0, x) + N� (−1) j Πp,j(0, x) and the Πp,n are appropriate functions (see Theorem 4.2 of [180]) involving nested expectations of quantities related to ‘double connections’. j=1
Percolation and Disordered Systems 223 We take Fourier transforms of (8.29), and solve to obtain that (8.30) �τp = �δp + �N j=1 (−1)jΠp,j � + (−1) N+1Rp,N � 1 − p� I� δp − p� I �N j=1 (−1)j � . Πp,j The convergence of the lace expansion, and the consequent validity of this formula for �τp, is obtained roughly as follows. First, one uses the BK inequality to derive bounds for the δp, Πp,j, Rp,j in terms of the functions T(p) and W(p). These bounds then imply bounds for the corresponding transforms. In this way, one may obtain a conclusion which is close to point (c) stated above.
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144 Geoffrey Grimmett ÈÊÇ��
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146 Geoffrey Grimmett 8. Critical P
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148 Geoffrey Grimmett θ(p) 1 pc 1
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150 Geoffrey Grimmett physical imag
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152 Geoffrey Grimmett Fig. 2.1. Par
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154 Geoffrey Grimmett Fig. 2.2. An
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156 Geoffrey Grimmett 3.1 Percolati
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158 Geoffrey Grimmett Kesten [201]
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160 Geoffrey Grimmett whence d dp P
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162 Geoffrey Grimmett Fig. 4.1. An
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164 Geoffrey Grimmett s 1 θ = 0 pc
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166 Geoffrey Grimmett ∂B(n) 0 e f
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168 Geoffrey Grimmett Fig. 4.5. A s
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170 Geoffrey Grimmett Theorem 5.5 (
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- Page 118 and 119: 258 Geoffrey Grimmett Theorem 11.13
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272 Geoffrey Grimmett which, via Le
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274 Geoffrey Grimmett Turning to th
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276 Geoffrey Grimmett Each circuit
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278 Geoffrey Grimmett If A(q) < 1 (
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280 Geoffrey Grimmett REFERENCES 1.
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282 Geoffrey Grimmett 30. Alexander
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284 Geoffrey Grimmett 63. Berg, J.
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286 Geoffrey Grimmett 93. Chayes, J
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288 Geoffrey Grimmett 123. Durrett,
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290 Geoffrey Grimmett 158. Grimmett
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292 Geoffrey Grimmett 191. Higuchi,
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294 Geoffrey Grimmett 224. Koteck´
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296 Geoffrey Grimmett 259. Meester,
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298 Geoffrey Grimmett 290. Newman,
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300 Geoffrey Grimmett 323. Roy, R.
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302 Geoffrey Grimmett 355. Wierman,