Narrow coverings of ω-ary product spaces

Narrow Coverings of Ω-ary Product Spaces

Results of Sierpiński and others have shown that certain finite-dimensional product sets can be written as unions of subsets, each of which is “narrow” in a corresponding direction; that is, each line in that direction intersects the subset in a small set. For example, if the set ω × ω is partitioned into two pieces along the diagonal, then one piece meets every horizontal line in a finite set,...

On Set Coverings in Cartesian Product Spaces

Appendix: On Set Coverings in Cartesian Product Spaces

Consider (X, E), where X is a finite set and E is a system of subsets whose union equals X. For every natural number n ∈ N define the cartesian products Xn = ∏n 1 X and En = ∏n 1 E . The following problem is investigated: how many sets of En are needed to cover Xn? Let this number be denoted by c(n). It is proved that for all n ∈ N exp{C · n} ≤ c(n) ≤ exp{Cn+ log n+ log log |X|}+ 1. A formula f...

A Product Decomposition of Ω

We give a specific product decomposition of the base-point path connected component of the triple loop space of the suspension of the projective plane.

Good coverings of Hamming spaces with spheres

The covering radius problem has been considered by many authors (e.g. [ 1, 5, 61). Finally, let t(n, k) be the minimum possible covering radius for an (n, k) code and k(n, p) the minimum possible dimension of a code with covering radius p. The study of t(n, k) was initiated by Karpovsky. For a survey of these questions, see ]41. The main goal of this paper is to find good linear coverings. The ...