CEU eTD Collection (2019); Galicza, Pál: Noise Stability versus Pivotals and Sparse Reconstruction of Functions in Spins Systems

CEU Electronic Theses and Dissertations, 2019
Author Galicza, Pál
Title Noise Stability versus Pivotals and Sparse Reconstruction of Functions in Spins Systems
Summary First we define $f_n$ for all $n$ large enough so that the $d = \mathrm{Diam}(F)$-ball on $G_n$ and on $G$ are isomorphic. Observe that it is sufficient to give an injection from $F$ onto $G_n$. Pick an arbitrary $r \in F$, and again an arbitrary $r' \in V_n$. Using the (rooted) isomorphism between the $d$-balls of $r$ in $G$ and $r'$ in $G_n$, we can find a bijection between the vertices of a subset $F_n$ in $G_n$ and $F$.
We start by proving the first statement. Define the sequence of ffIID measures $\nu_n$ on $G$ as follows. For every $v \in V$ we run the algorithm $\phi$ restricted to the ball $B_n(v)$. If the spin value $\sigma_{v}$ can be calculated from $B_n(v)$ (where $\sigma$ is distributed according to $\mu$), then we write the respective spin value, otherwise we flip a coin independent from everything else, according to the distribution of $\sigma_{v}$ conditioned on $B_n(v)$. It is clear that $\nu_n \xrightarrow{a. s.} \mu$ and that $\lim_{n \rightarrow \infty}{S_{\nu_n}(f)}= S_{\mu}(f)$. Therefore we can choose
Fix a large number $L$ and choose a finite subset $H \subset \mathsf{Aut}(G)$ in such a way, that $\sum_{g \in H}{|\Cov(f, f^g)|} > L$. For an arbitrary $v \in F$ we may choose a large, but fix $r$ in such a way that $\bigcup_{g\in H} F^{g} \subseteq B_r(v) $.
Supervisor Gabor, Pete
Department Mathematics PhD
Full texthttps://www.etd.ceu.edu/2019/galicza_pal.pdf

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