Sparse reconstruction in spin systems II: Ising and other factor of IID measures
Pál Galicza, Gábor Pete
备注：
77 pages. Minor corrections throughout, and a small reorganization that includes a change in the numbering of the Open Problems. To appear in Probability Theory & Related Fields
For a sequence of Boolean functions $f_n : \{-1, 1\}^{V_n} \longrightarrow \{-1, 1\}$, with random input given by some probability measure $\mathbb{P}_n$, we say that there is sparse reconstruction for $f_n$ if there is a sequence of subsets $U_n \subseteq V_n$ of coordinates satisfying $|U_n| = o(|V_n|)$ such that knowing the spins in $U_n$ gives us a non-vanishing amount of information about the value of $f_n$.
In the first part of this work, we showed that if the $\mathbb{P}_n$s are product measures, then no sparse reconstruction is possible for any sequence of transitive functions. In this sequel, we consider spin systems that are relatives of IID measures in one way or another, with our main focus being on the Ising model on finite transitive graphs or exhaustions of lattices. We prove that no sparse reconstruction is possible for the entire high temperature regime on Euclidean boxes and the Curie-Weiss model, while sparse reconstruction for the majority function of the spins is possible in the critical and low temperature regimes. We give quantitative bounds for two-dimensional boxes and the Curie-Weiss model, sharp in the latter case.
The proofs employ several different methods, including factor of IID and FK random cluster representations, strong spatial mixing, a generalization of discrete Fourier analysis to Divide-and-Color models, and entropy inequalities.
We study the ferromagnetic Ising model on the infinite $d$-regular tree under the free boundary condition. This model is known to be a factor of IID in the uniqueness regime, when the inverse temperature $β\ge 0$ satisfies $\tanh β\le (d-1)^{-1}$. However, in the reconstruction regime ($\tanh β> (d-1)^{-\frac{1}{2}}$), it is not a factor of IID. We construct a factor of IID for the Ising model beyond the uniqueness regime via a strong solution to an infinite dimensional stochastic differential equation which partially answers a question of Lyons. The solution $\{X_t(v) \}$ of the SDE is distri…
Central Limit Theorems for Finitary Factors of iid Processes
Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学）；University of Bristol（布里斯托大学）；The Hebrew University of Jerusalem（耶路撒冷希伯来大学）；Weizmann Institute of Science（魏茨曼科学研究所）
Approximating the partition function of the ferromagnetic Ising model with general external fields is known to be #BIS-hard in the worst case, even for bounded-degree graphs, and it is widely believed that no polynomial-time approximation scheme exists. This motivates an average-case question: are there classes of instances for which polynomial-time approximation schemes exist? We investigate this question for the random field Ising model on graphs with maximum degree $Δ$. We establish the existence of fully polynomial-time approximation schemes and samplers with high probability over the rand…
We show that a nearly square iid random integral matrix is surjective over the integral lattice with very high probability. This answers a question by Koplewitz. Our result extends to sparse matrices as well as to matrices of dependent entries.
We prove that the reverse characteristic polynomial $\det(I_n - zA_n)$ of a random $n \times n$ matrix $A_n$ with iid $\mathrm{Bernoulli}(d/n)$ entries converges in distribution towards the random infinite product $\prod_{\ell = 1}^\infty(1-z^\ell)^{Y_\ell}$ where $Y_\ell$ are independent $\mathrm{Poisson}(d^\ell/\ell)$ random variables. We show that this random function is a Poisson analog of more classical Gaussian objects such as the Gaussian holomorphic chaos. As a byproduct, we obtain new simple proofs of previous results on the asymptotic behaviour of extremal eigenvalues of sparse Erdős…
