Hales–Jewett theorem
Source: Iran PPCE 2004
January 9, 2009
geometry3D geometrycombinatorics proposedcombinatorics
Problem Statement
Let be natural numbers. We want to prove that for large numbers , for each -coloring of the -dimensional cube with side length , there is a -dimensional subspace that all of its vertices have the same color. Let be the least number such that for the previus statement holds.
a) Prove that:
H(l,d \plus{} 1,k)\leq H(l,1,k) \plus{} H(l,d,k^l)^{H(l,1,k)}
b) Prove that
H(l \plus{} 1,1,k \plus{} 1)\leq H(l,1 \plus{} H(l \plus{} 1,1,k),k \plus{} 1)
c) Prove the statement of problem.
d) Prove Van der Waerden's Theorem.