English

On the compatibility of binary sequences

Probability 2012-04-17 v1

Abstract

An ordered pair of semi-infinite binary sequences (η,ξ)(\eta,\xi) is said to be compatible if there is a way of removing a certain number (possibly infinite) of ones from η\eta and zeroes from ξ\xi, whichwould map both sequences to the same semi-infinite sequence. This notion was introduced by Peter Winkler, who also posed the following question: η\eta and ξ\xi being independent i.i.d. Bernoulli sequences with parameters pp^\prime and pp respectively, does it exist (p,p)(p', p) so that the set of compatible pairs has positive measure? It is known that this does not happen for pp and pp^\prime very close to 1/2. In the positive direction, we construct, for any ϵ>0\epsilon > 0, a deterministic binary sequence ηϵ\eta_\epsilon whose set of zeroes has Hausdorff dimension larger than 1ϵ1-\epsilon, and such that Ppξ ⁣:(ηϵ,ξ)is compatible>0\mathbb{P}_p {\xi\colon (\eta_\epsilon,\xi) \text {is compatible}} > 0 for pp small enough, where Pp\mathbb{P}_p stands for the product Bernoulli measure with parameter pp.

Cite

@article{arxiv.1204.3197,
  title  = {On the compatibility of binary sequences},
  author = {Harry Kesten and Bernardo N. B. de Lima and Vladas Sidoravicius and Maria Eulália Vares},
  journal= {arXiv preprint arXiv:1204.3197},
  year   = {2012}
}

Comments

32 pages, 5 figures

R2 v1 2026-06-21T20:49:28.904Z