Biased partitions of $\mathbb{Z}^n$
Abstract
Given a function on the vertex set of some graph , a scenery, let a simple random walk run over the graph and produce a sequence of values. Is it possible to, with high probability, reconstruct the scenery from this random sequence? To show this is impossible for some graphs, Gross and Grupel, call a function on the vertex set of a graph -biased if for each vertex the fraction of neighbours on which is 1 is exactly . Clearly, two -biased functions are indistinguishable based on their sceneries. Gross and Grupel construct -biased functions on the hypercube and ask for what there exist -biased functions on and additionally how many there are. We fully answer this question by giving a complete characterization of these values of . We show that -biased functions exist for all with and, in fact, there are uncountably many of them for every . To this end, we construct uncountably many partitions of into parts such that every element of has exactly one neighbour in each part. This additionally shows that not all sceneries on can be reconstructed from a sequence of values on attained on a simple random walk.
Cite
@article{arxiv.1805.05283,
title = {Biased partitions of $\mathbb{Z}^n$},
author = {Peter van Hintum},
journal= {arXiv preprint arXiv:1805.05283},
year = {2020}
}
Comments
10 pages