Abstract

A structure A = (A; E₀, E₁ , . . . , ${E_{n - 2}}$) is an n-grid if each E i is an equivalence relation on A and whenver X and Y are equivalence classes of, repectively, distinct E i and E j , then X ∩ Y is finite. A coloring χ : A → n is acceptable if whenver X is an equivalence class of E i , then {ϰ Є X: χ(ϰ) = i} is finite. If B is any set, then the n-cube B n = (B n ; E₀ E₁ , . . . , ${E_{n - 2}}$) is considinate axis. Kuratowski [9], generalizing the n = 3 case proved by Sierpiński [17], proved that ℝ n has an acceptable coloring iff ${2^{{N_0}}}$ ≤ ${N_{n - 2}}$. The main result is: of A is a semialgebraic (i.e., first-order definable in the field of reals) n-grid, then the following are equivalent: (1) if A embeds all finite n-cubes, then ${2^{{N_0}}}$ ≤ ${N_{n - 2}}$; if A embeds ℝ n , then ${2^{{N_0}}}$ ≤ ${N_{n - 2}}$; (3) A has an acceptable coloring