lemmaroutine

Edge height cost controls point-pair height cost

Lemma·ht:transfer·§4.3 Excluding bounded total variation

Statement (paper)

Suppose a probability law ω\omega on two finite vertex sets P×QP\times Q, with point marginal μ\mu, has the following property: for all assignments of finite labels to its vertices, two independent μ\mu-points disagree with probability at most C0C_0 times the edge disagreement probability. For any coordinate U:P∪Q→NU:P\cup Q\to\mathcal N, Ep,p′∼μh(Up−Up′)≤C1(E(p,q)∼ωh(Up−Uq)+1), \E_{p,p'\sim\mu}h(U_p-U_{p'}) \le C_1\bigl(\E_{(p,q)\sim\omega}h(U_p-U_q)+1\bigr), where C1C_1 depends only on C0C_0.

In plain English

If a probability law ω\omega on P×QP\times Q with point marginal μ\mu is such that, for every finite labelling of vertices, two independent μ\mu-points disagree with probability at most C0C_0 times the edge disagreement probability, then for any coordinate U:P∪Q→NU:P\cup Q\to\mathcal N the average of h(Up−Up′)h(U_p-U_{p'}) over independent p,p′∼μp,p'\sim\mu is at most C1C_1 times (the average of h(Up−Uq)h(U_p-U_q) over edges (p,q)∼ω(p,q)\sim\omega, plus 1), with C1C_1 depending only on C0C_0.

Why it's here

This lemma transfers the label-disagreement hypothesis into a bound on the height function hh, so that the height of differences between arbitrary pairs of points is controlled by the height along edges. This lets later arguments (such as ruling out bounded SS) pass from small edge heights to small heights between independent points.
Classified routine:
Follows from the label-disagreement (expansion/Cheeger-type) hypothesis by a standard layer-cake argument: apply the hypothesis to dyadic level-set labellings of the height function hh and sum over scales.

Sources

PaperOpen
Section
§4.3 Excluding bounded total variation
Page
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Label
ht:transfer
Line
sections/03-heights.tex:174
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