OAI.SKRatio.ratio_cutoff

The theorem states that, for real parameters β with 0 ≤ β < 1/2, ε with 0 < ε < 1/2, and η > 0, two things hold for the Sherrington–Kirkpatrick model with n spins, where a disorder g is a real coupling for each pair i < j of sites and the Gibbs measure at zero external field has weight proportional to exp((1/2) Σᵢ Σⱼ σᵢ gᵢⱼ σⱼ) on spin configurations σ ∈ {±1}ⁿ (couplings symmetrized, diagonal zero). The dynamics is a heat-bath single-site chain: choose a site uniformly at random, then keep or flip its spin with probabilities proportional to the Gibbs masses of the two configurations (for n = 0 the transition matrix is the identity). The distance after k steps is the maximum over starting configurations of the total variation distance (half the ℓ¹ distance) between the k-step distribution and the Gibbs measure, and mixingTime(g, δ) is the least k whose distance is at most δ (the infimum of the set, so 0 if that set is empty). The disorder law makes the couplings independent centered Gaussians with variance β²/n. First, the probability under this law that the ratio mixingTime(g, ε) / mixingTime(g, 1 − ε) exceeds 1 + η tends to 0 as n → ∞. Second, for all sufficiently large n, every disorder g satisfies mixingTime(g, 1 − ε) > 0.